Discussion:
A mechanical phase locked loop!
(too old to reply)
Gareth's Downstairs Computer
2017-08-01 11:00:33 UTC
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Raw Message
Continuing my googling following last night's
BHI lecture, and following up on the Shortt
and Hope-jones clocks, here is a mechanical
phase locked loop, and in Meccano! ...

http://www.meccanotec.com/shortt.html
Brian Reay
2017-08-01 11:58:56 UTC
Permalink
Raw Message
Post by Gareth's Downstairs Computer
Continuing my googling following last night's
BHI lecture, and following up on the Shortt
and Hope-jones clocks, here is a mechanical
phase locked loop, and in Meccano! ...
http://www.meccanotec.com/shortt.html
While the article refers to a 'phase lock loop', it isn't really.. There
doesn't seem to be any measurement of error in the slave which is then
use use used to 'pull it' to reduce the error- which is how a true phase
lock loop works.

The system seems to operate more as follows, the slave is designed to
run 'very nearly right'. It receives precise pulses from the master
which it will naturally sync to. The same will happen if you have two
oscillators on nearly the same frequency if you 'feed' the output of one
to the tuned circuit of the other. (Including harmonics.) This is used,
for example, by some amateurs to lock radio oscillators to GPS locked
references.

Still, it is an clever system and of interest.
rickman
2017-08-01 12:49:55 UTC
Permalink
Raw Message
Post by Brian Reay
Post by Gareth's Downstairs Computer
Continuing my googling following last night's
BHI lecture, and following up on the Shortt
and Hope-jones clocks, here is a mechanical
phase locked loop, and in Meccano! ...
http://www.meccanotec.com/shortt.html
While the article refers to a 'phase lock loop', it isn't really.. There
doesn't seem to be any measurement of error in the slave which is then use
use used to 'pull it' to reduce the error- which is how a true phase lock
loop works.
The system seems to operate more as follows, the slave is designed to run
'very nearly right'. It receives precise pulses from the master which it
will naturally sync to. The same will happen if you have two oscillators on
nearly the same frequency if you 'feed' the output of one to the tuned
circuit of the other. (Including harmonics.) This is used, for example, by
some amateurs to lock radio oscillators to GPS locked references.
Still, it is an clever system and of interest.
The Shortt clock *does* make a measurement of the phase. It checks to see
if the phase is fast or slow. In one case it invokes a spring that tweeks
the phase of the slave. In the other case it does not invoke the spring
allowing the clock to continue running unadjusted. The default behavior of
the slave clock is to run a bit slow and the adjustments speed it up (or the
other way round, I can't recall exactly).

The measurement may be binary and the adjustment is the same, but that does
not make it anything other than a phase locked loop.
--
Rick C
Brian Reay
2017-08-01 17:19:14 UTC
Permalink
Raw Message
Post by rickman
Post by Brian Reay
Post by Gareth's Downstairs Computer
Continuing my googling following last night's
BHI lecture, and following up on the Shortt
and Hope-jones clocks, here is a mechanical
phase locked loop, and in Meccano! ...
http://www.meccanotec.com/shortt.html
While the article refers to a 'phase lock loop', it isn't really.. There
doesn't seem to be any measurement of error in the slave which is then use
use used to 'pull it' to reduce the error- which is how a true phase lock
loop works.
The system seems to operate more as follows, the slave is designed to run
'very nearly right'. It receives precise pulses from the master which it
will naturally sync to. The same will happen if you have two
oscillators on
nearly the same frequency if you 'feed' the output of one to the tuned
circuit of the other. (Including harmonics.) This is used, for example, by
some amateurs to lock radio oscillators to GPS locked references.
Still, it is an clever system and of interest.
The Shortt clock *does* make a measurement of the phase. It checks to
see if the phase is fast or slow. In one case it invokes a spring that
tweeks the phase of the slave. In the other case it does not invoke the
spring allowing the clock to continue running unadjusted. The default
behavior of the slave clock is to run a bit slow and the adjustments
speed it up (or the other way round, I can't recall exactly).
The measurement may be binary and the adjustment is the same, but that
does not make it anything other than a phase locked loop.
Hmm, I half see your point but I'm not entirely convinced.

I'm just not convinced that the description truly 'maps' to that of a
true PLL.

I don't doubt that it works nor do I suggest it isn't a very clever bit
of design. I'm just not sure about the terms used.
rickman
2017-08-02 03:59:18 UTC
Permalink
Raw Message
Post by Brian Reay
Post by rickman
Post by Brian Reay
Post by Gareth's Downstairs Computer
Continuing my googling following last night's
BHI lecture, and following up on the Shortt
and Hope-jones clocks, here is a mechanical
phase locked loop, and in Meccano! ...
http://www.meccanotec.com/shortt.html
While the article refers to a 'phase lock loop', it isn't really.. There
doesn't seem to be any measurement of error in the slave which is then use
use used to 'pull it' to reduce the error- which is how a true phase lock
loop works.
The system seems to operate more as follows, the slave is designed to run
'very nearly right'. It receives precise pulses from the master which it
will naturally sync to. The same will happen if you have two oscillators on
nearly the same frequency if you 'feed' the output of one to the tuned
circuit of the other. (Including harmonics.) This is used, for example, by
some amateurs to lock radio oscillators to GPS locked references.
Still, it is an clever system and of interest.
The Shortt clock *does* make a measurement of the phase. It checks to see
if the phase is fast or slow. In one case it invokes a spring that tweeks
the phase of the slave. In the other case it does not invoke the spring
allowing the clock to continue running unadjusted. The default behavior
of the slave clock is to run a bit slow and the adjustments speed it up
(or the other way round, I can't recall exactly).
The measurement may be binary and the adjustment is the same, but that
does not make it anything other than a phase locked loop.
Hmm, I half see your point but I'm not entirely convinced.
I'm just not convinced that the description truly 'maps' to that of a true PLL.
I don't doubt that it works nor do I suggest it isn't a very clever bit of
design. I'm just not sure about the terms used.
Ok, but I don't see what you can be confused about. I believe in
electronics this phase detector is referred to as "bang-bang" where it
outputs a 1 or a 0. So on every measurement the VCO frequency control
signal receives an impulse of one polarity or the other.

The only difference between that and the Shortt clock is the Short clock
only has one polarity of impulse and is adjusted to run a bit off so the
required intermittent impulses will keep it in phase with the master.

If you are interested in mechanical clocks (the Shortt clock uses
electricity to isolate the master and slave even though the master is purely
mechanical) you can read about the Fedchenko AChF-3 time piece. It came
well after the Shortt clock and not long before quartz and atomic clocks,
but was amazingly accurate without any fancy footwork with master slave
complexity.

Fedchenko used a compound spring for want of a better name. I've read that
it corrects for the parabolic distortion introduced in the timing of a
circular pendulum swing. This is a second order effect in that the
coefficient in the term is rather small. But in these clocks it makes a
difference. The way most clocks correct for it is to keep the amplitude of
the pendulum swing as constant as possible minimizing the second order
deviation. The Fedchenko clock uses a pendulum spring with two distinct
lengths. This causes a different rate of spring over the range of angle.
Some descriptions seem to say it actually causes the pendulum to swing in a
parabolic arc. Either way it corrects for the second order term in the time
equation of the pendulum making it less sensitive to variations in the
amplitude of oscillation.
--
Rick C
rickman
2017-08-02 04:08:28 UTC
Permalink
Raw Message
Post by rickman
Post by Brian Reay
Post by rickman
Post by Brian Reay
Post by Gareth's Downstairs Computer
Continuing my googling following last night's
BHI lecture, and following up on the Shortt
and Hope-jones clocks, here is a mechanical
phase locked loop, and in Meccano! ...
http://www.meccanotec.com/shortt.html
While the article refers to a 'phase lock loop', it isn't really.. There
doesn't seem to be any measurement of error in the slave which is then use
use used to 'pull it' to reduce the error- which is how a true phase lock
loop works.
The system seems to operate more as follows, the slave is designed to run
'very nearly right'. It receives precise pulses from the master which it
will naturally sync to. The same will happen if you have two oscillators on
nearly the same frequency if you 'feed' the output of one to the tuned
circuit of the other. (Including harmonics.) This is used, for example, by
some amateurs to lock radio oscillators to GPS locked references.
Still, it is an clever system and of interest.
The Shortt clock *does* make a measurement of the phase. It checks to see
if the phase is fast or slow. In one case it invokes a spring that tweeks
the phase of the slave. In the other case it does not invoke the spring
allowing the clock to continue running unadjusted. The default behavior
of the slave clock is to run a bit slow and the adjustments speed it up
(or the other way round, I can't recall exactly).
The measurement may be binary and the adjustment is the same, but that
does not make it anything other than a phase locked loop.
Hmm, I half see your point but I'm not entirely convinced.
I'm just not convinced that the description truly 'maps' to that of a true PLL.
I don't doubt that it works nor do I suggest it isn't a very clever bit of
design. I'm just not sure about the terms used.
Ok, but I don't see what you can be confused about. I believe in
electronics this phase detector is referred to as "bang-bang" where it
outputs a 1 or a 0. So on every measurement the VCO frequency control
signal receives an impulse of one polarity or the other.
The only difference between that and the Shortt clock is the Short clock
only has one polarity of impulse and is adjusted to run a bit off so the
required intermittent impulses will keep it in phase with the master.
If you are interested in mechanical clocks (the Shortt clock uses
electricity to isolate the master and slave even though the master is purely
mechanical) you can read about the Fedchenko AChF-3 time piece. It came
well after the Shortt clock and not long before quartz and atomic clocks,
but was amazingly accurate without any fancy footwork with master slave
complexity.
Fedchenko used a compound spring for want of a better name. I've read that
it corrects for the parabolic distortion introduced in the timing of a
circular pendulum swing. This is a second order effect in that the
coefficient in the term is rather small. But in these clocks it makes a
difference. The way most clocks correct for it is to keep the amplitude of
the pendulum swing as constant as possible minimizing the second order
deviation. The Fedchenko clock uses a pendulum spring with two distinct
lengths. This causes a different rate of spring over the range of angle.
Some descriptions seem to say it actually causes the pendulum to swing in a
parabolic arc. Either way it corrects for the second order term in the time
equation of the pendulum making it less sensitive to variations in the
amplitude of oscillation.
Thought I'd mention John Harrison's 'Clock B' too. It was designed 250
years ago, but never built that I am aware of until recently. It has proved
to be nearly as accurate as the Shortt and Fedchenko clocks even though it
was a much, much earlier design. I don't know any details of why it is so
good other than that Harrison took into account every source of error and
included a compensating factor to balance it out. I haven't see any further
detail. Pretty impressive. Clearly the man was a genius.
--
Rick C
Brian Reay
2017-08-02 07:19:51 UTC
Permalink
Raw Message
Post by rickman
Post by rickman
Post by Brian Reay
Post by rickman
Post by Brian Reay
Post by Gareth's Downstairs Computer
Continuing my googling following last night's
BHI lecture, and following up on the Shortt
and Hope-jones clocks, here is a mechanical
phase locked loop, and in Meccano! ...
http://www.meccanotec.com/shortt.html
While the article refers to a 'phase lock loop', it isn't really.. There
doesn't seem to be any measurement of error in the slave which is then use
use used to 'pull it' to reduce the error- which is how a true phase lock
loop works.
The system seems to operate more as follows, the slave is designed to run
'very nearly right'. It receives precise pulses from the master which it
will naturally sync to. The same will happen if you have two oscillators on
nearly the same frequency if you 'feed' the output of one to the tuned
circuit of the other. (Including harmonics.) This is used, for example, by
some amateurs to lock radio oscillators to GPS locked references.
Still, it is an clever system and of interest.
The Shortt clock *does* make a measurement of the phase. It checks to see
if the phase is fast or slow. In one case it invokes a spring that tweeks
the phase of the slave. In the other case it does not invoke the spring
allowing the clock to continue running unadjusted. The default behavior
of the slave clock is to run a bit slow and the adjustments speed it up
(or the other way round, I can't recall exactly).
The measurement may be binary and the adjustment is the same, but that
does not make it anything other than a phase locked loop.
Hmm, I half see your point but I'm not entirely convinced.
I'm just not convinced that the description truly 'maps' to that of a
true
PLL.
I don't doubt that it works nor do I suggest it isn't a very clever bit of
design. I'm just not sure about the terms used.
Ok, but I don't see what you can be confused about. I believe in
electronics this phase detector is referred to as "bang-bang" where it
outputs a 1 or a 0. So on every measurement the VCO frequency control
signal receives an impulse of one polarity or the other.
The only difference between that and the Shortt clock is the Short clock
only has one polarity of impulse and is adjusted to run a bit off so the
required intermittent impulses will keep it in phase with the master.
If you are interested in mechanical clocks (the Shortt clock uses
electricity to isolate the master and slave even though the master is purely
mechanical) you can read about the Fedchenko AChF-3 time piece. It came
well after the Shortt clock and not long before quartz and atomic clocks,
but was amazingly accurate without any fancy footwork with master slave
complexity.
Fedchenko used a compound spring for want of a better name. I've read that
it corrects for the parabolic distortion introduced in the timing of a
circular pendulum swing. This is a second order effect in that the
coefficient in the term is rather small. But in these clocks it makes a
difference. The way most clocks correct for it is to keep the amplitude of
the pendulum swing as constant as possible minimizing the second order
deviation. The Fedchenko clock uses a pendulum spring with two distinct
lengths. This causes a different rate of spring over the range of angle.
Some descriptions seem to say it actually causes the pendulum to swing in a
parabolic arc. Either way it corrects for the second order term in the time
equation of the pendulum making it less sensitive to variations in the
amplitude of oscillation.
Thought I'd mention John Harrison's 'Clock B' too. It was designed 250
years ago, but never built that I am aware of until recently. It has
proved to be nearly as accurate as the Shortt and Fedchenko clocks even
though it was a much, much earlier design. I don't know any details of
why it is so good other than that Harrison took into account every
source of error and included a compensating factor to balance it out. I
haven't see any further detail. Pretty impressive. Clearly the man was
a genius.
Oh yes, I recall the B clock- I have an interest in clocks (actually
more watches) - and read up on Harrison's history, partly due to his
work on clocks / watches directly but also as much of my engineering
work was navigation related.

I recall reading of the building of the modern version of the B clock -
it must have been in the 70s or early 80s.

As you say, Harrison was a genius- albeit an largely unrecognised /
unappreciated one in his own time- at least by the Gov. of the day. I've
seen the examples of his work in the National Maritime Museum- the
quality is unbelievable, especially when you consider the technology of
the time.
--
Suspect someone is claiming a benefit under false pretences? Incapacity
Benefit or Personal Independence Payment when they don't need it? They
are depriving those in real need!

https://www.gov.uk/report-benefit-fraud
Chris
2017-08-03 12:43:55 UTC
Permalink
Raw Message
Post by Brian Reay
Post by Brian Reay
Post by Brian Reay
Post by Gareth's Downstairs Computer
Continuing my googling following last night's
BHI lecture, and following up on the Shortt
and Hope-jones clocks, here is a mechanical
phase locked loop, and in Meccano! ...
http://www.meccanotec.com/shortt.html
While the article refers to a 'phase lock loop', it isn't really.. There
doesn't seem to be any measurement of error in the slave which is then use
use used to 'pull it' to reduce the error- which is how a true phase lock
loop works.
The system seems to operate more as follows, the slave is designed to run
'very nearly right'. It receives precise pulses from the master which it
will naturally sync to. The same will happen if you have two oscillators on
nearly the same frequency if you 'feed' the output of one to the tuned
circuit of the other. (Including harmonics.) This is used, for example, by
some amateurs to lock radio oscillators to GPS locked references.
Still, it is an clever system and of interest.
The Shortt clock *does* make a measurement of the phase. It checks
to see
if the phase is fast or slow. In one case it invokes a spring that
tweeks
the phase of the slave. In the other case it does not invoke the
spring
allowing the clock to continue running unadjusted. The default
behavior
of the slave clock is to run a bit slow and the adjustments speed it up
(or the other way round, I can't recall exactly).
The measurement may be binary and the adjustment is the same, but that
does not make it anything other than a phase locked loop.
Hmm, I half see your point but I'm not entirely convinced.
I'm just not convinced that the description truly 'maps' to that of a
true
PLL.
I don't doubt that it works nor do I suggest it isn't a very clever bit of
design. I'm just not sure about the terms used.
Ok, but I don't see what you can be confused about. I believe in
electronics this phase detector is referred to as "bang-bang" where it
outputs a 1 or a 0. So on every measurement the VCO frequency control
signal receives an impulse of one polarity or the other.
The only difference between that and the Shortt clock is the Short clock
only has one polarity of impulse and is adjusted to run a bit off so the
required intermittent impulses will keep it in phase with the master.
If you are interested in mechanical clocks (the Shortt clock uses
electricity to isolate the master and slave even though the master is purely
mechanical) you can read about the Fedchenko AChF-3 time piece. It came
well after the Shortt clock and not long before quartz and atomic clocks,
but was amazingly accurate without any fancy footwork with master slave
complexity.
Fedchenko used a compound spring for want of a better name. I've read
that
it corrects for the parabolic distortion introduced in the timing of a
circular pendulum swing. This is a second order effect in that the
coefficient in the term is rather small. But in these clocks it makes a
difference. The way most clocks correct for it is to keep the
amplitude of
the pendulum swing as constant as possible minimizing the second order
deviation. The Fedchenko clock uses a pendulum spring with two distinct
lengths. This causes a different rate of spring over the range of angle.
Some descriptions seem to say it actually causes the pendulum to swing in a
parabolic arc. Either way it corrects for the second order term in
the time
equation of the pendulum making it less sensitive to variations in the
amplitude of oscillation.
Thought I'd mention John Harrison's 'Clock B' too. It was designed 250
years ago, but never built that I am aware of until recently. It has
proved to be nearly as accurate as the Shortt and Fedchenko clocks even
though it was a much, much earlier design. I don't know any details of
why it is so good other than that Harrison took into account every
source of error and included a compensating factor to balance it out. I
haven't see any further detail. Pretty impressive. Clearly the man was
a genius.
Oh yes, I recall the B clock- I have an interest in clocks (actually
more watches) - and read up on Harrison's history, partly due to his
work on clocks / watches directly but also as much of my engineering
work was navigation related.
I recall reading of the building of the modern version of the B clock -
it must have been in the 70s or early 80s.
As you say, Harrison was a genius- albeit an largely unrecognised /
unappreciated one in his own time- at least by the Gov. of the day. I've
seen the examples of his work in the National Maritime Museum- the
quality is unbelievable, especially when you consider the technology of
the time.
I've had an interest in clocks as well. Working in computing, was
interested in the IBM master clocks, which have a Graham deadbeat
escapement and either an electrically wound spring, or weight
driven mechanism, + an Invar pendulum. Found a mid 1930's
example some time ago, which has been running now for about a
year. Stripped down completely and rebuilt. IBM claim around 15
seconds a month error, but after rating for a few weeks, it shows
an error of less than a second a month. There's noise on the
stability, drifting +/- half a second or so from day to day, but
was quite amazed at the accuracy of such an old clock...

Chris
Brian Reay
2017-08-03 13:44:46 UTC
Permalink
Raw Message
Post by Chris
Post by Brian Reay
Post by Brian Reay
Post by Brian Reay
Post by Gareth's Downstairs Computer
Continuing my googling following last night's
BHI lecture, and following up on the Shortt
and Hope-jones clocks, here is a mechanical
phase locked loop, and in Meccano! ...
http://www.meccanotec.com/shortt.html
While the article refers to a 'phase lock loop', it isn't really.. There
doesn't seem to be any measurement of error in the slave which is then use
use used to 'pull it' to reduce the error- which is how a true phase lock
loop works.
The system seems to operate more as follows, the slave is designed to run
'very nearly right'. It receives precise pulses from the master which it
will naturally sync to. The same will happen if you have two oscillators on
nearly the same frequency if you 'feed' the output of one to the tuned
circuit of the other. (Including harmonics.) This is used, for example, by
some amateurs to lock radio oscillators to GPS locked references.
Still, it is an clever system and of interest.
The Shortt clock *does* make a measurement of the phase. It checks
to see
if the phase is fast or slow. In one case it invokes a spring that
tweeks
the phase of the slave. In the other case it does not invoke the
spring
allowing the clock to continue running unadjusted. The default
behavior
of the slave clock is to run a bit slow and the adjustments speed it up
(or the other way round, I can't recall exactly).
The measurement may be binary and the adjustment is the same, but that
does not make it anything other than a phase locked loop.
Hmm, I half see your point but I'm not entirely convinced.
I'm just not convinced that the description truly 'maps' to that of a
true
PLL.
I don't doubt that it works nor do I suggest it isn't a very clever bit of
design. I'm just not sure about the terms used.
Ok, but I don't see what you can be confused about. I believe in
electronics this phase detector is referred to as "bang-bang" where it
outputs a 1 or a 0. So on every measurement the VCO frequency control
signal receives an impulse of one polarity or the other.
The only difference between that and the Shortt clock is the Short clock
only has one polarity of impulse and is adjusted to run a bit off so the
required intermittent impulses will keep it in phase with the master.
If you are interested in mechanical clocks (the Shortt clock uses
electricity to isolate the master and slave even though the master is purely
mechanical) you can read about the Fedchenko AChF-3 time piece. It came
well after the Shortt clock and not long before quartz and atomic clocks,
but was amazingly accurate without any fancy footwork with master slave
complexity.
Fedchenko used a compound spring for want of a better name. I've read
that
it corrects for the parabolic distortion introduced in the timing of a
circular pendulum swing. This is a second order effect in that the
coefficient in the term is rather small. But in these clocks it makes a
difference. The way most clocks correct for it is to keep the
amplitude of
the pendulum swing as constant as possible minimizing the second order
deviation. The Fedchenko clock uses a pendulum spring with two distinct
lengths. This causes a different rate of spring over the range of angle.
Some descriptions seem to say it actually causes the pendulum to swing in a
parabolic arc. Either way it corrects for the second order term in
the time
equation of the pendulum making it less sensitive to variations in the
amplitude of oscillation.
Thought I'd mention John Harrison's 'Clock B' too. It was designed 250
years ago, but never built that I am aware of until recently. It has
proved to be nearly as accurate as the Shortt and Fedchenko clocks even
though it was a much, much earlier design. I don't know any details of
why it is so good other than that Harrison took into account every
source of error and included a compensating factor to balance it out. I
haven't see any further detail. Pretty impressive. Clearly the man was
a genius.
Oh yes, I recall the B clock- I have an interest in clocks (actually
more watches) - and read up on Harrison's history, partly due to his
work on clocks / watches directly but also as much of my engineering
work was navigation related.
I recall reading of the building of the modern version of the B clock -
it must have been in the 70s or early 80s.
As you say, Harrison was a genius- albeit an largely unrecognised /
unappreciated one in his own time- at least by the Gov. of the day. I've
seen the examples of his work in the National Maritime Museum- the
quality is unbelievable, especially when you consider the technology of
the time.
I've had an interest in clocks as well. Working in computing, was
interested in the IBM master clocks, which have a Graham deadbeat
escapement and either an electrically wound spring, or weight
driven mechanism, + an Invar pendulum. Found a mid 1930's
example some time ago, which has been running now for about a
year. Stripped down completely and rebuilt. IBM claim around 15
seconds a month error, but after rating for a few weeks, it shows
an error of less than a second a month. There's noise on the
stability, drifting +/- half a second or so from day to day, but
was quite amazed at the accuracy of such an old clock...
Chris
I used to have a small, but nice, collection of pocket watches. I'd
collected them over the years, repaired them etc. Then some scum bag
thieved them. While I got a generous insurance payment, it wasn't the
same. I'd put 'sweat and blood' into them- they were in a poor state
when I got them but valuable when I'd restored them. I was tempted to
buy some more to restore but never got around to it- time was always
short. Now my dexterity isn't what it could be and I probably would
struggle with a pocket watch, let alone a wrist watch. One had a
cylinder escapement, not rare, but unusual and with a distinct 'tick'-
different to a normal escapement.

While I prefer mechanical watches, I favour Rolex (originally English,
BTW), I would quite like to get one of the 'tuning fork' watches,
ideally the version with the clear dial. Another classic.
Chris
2017-08-03 15:15:25 UTC
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Post by Brian Reay
While I prefer mechanical watches, I favour Rolex (originally English,
BTW), I would quite like to get one of the 'tuning fork' watches,
ideally the version with the clear dial. Another classic.
Bulova Accutron. You can find them on US Ebay, not cheap, but even
the example with the exposed internals. Pretty neat watches, but not
sure how accurate they would be by now. Also like the early Junghans
Mega msf clocks. Bought one of those around 1990. Still keeps spot
on time and use it to rate the IBM clock and others...

Chris
Jeff
2017-08-02 09:09:53 UTC
Permalink
Raw Message
Post by rickman
Post by Brian Reay
I don't doubt that it works nor do I suggest it isn't a very clever bit of
design. I'm just not sure about the terms used.
Ok, but I don't see what you can be confused about. I believe in
electronics this phase detector is referred to as "bang-bang" where it
outputs a 1 or a 0. So on every measurement the VCO frequency control
signal receives an impulse of one polarity or the other.
I think the confusion occurs because at no time, are the phases of the 2
clocks locked together, even at the point of the impulse. By the very
nature of the design the phase of the 2 pendulums (or should that be
pendula to please Gareth) shift in relation to each other.

In an electronic pll, even one using a bang-bang phase detector, the
phases of the 2 signals are locked together, within the constraints of
the loop filter.

Jeff
rickman
2017-08-02 14:04:19 UTC
Permalink
Raw Message
Post by Jeff
Post by rickman
Post by Brian Reay
I don't doubt that it works nor do I suggest it isn't a very clever bit of
design. I'm just not sure about the terms used.
Ok, but I don't see what you can be confused about. I believe in
electronics this phase detector is referred to as "bang-bang" where it
outputs a 1 or a 0. So on every measurement the VCO frequency control
signal receives an impulse of one polarity or the other.
I think the confusion occurs because at no time, are the phases of the 2
clocks locked together, even at the point of the impulse. By the very nature
of the design the phase of the 2 pendulums (or should that be pendula to
please Gareth) shift in relation to each other.
In an electronic pll, even one using a bang-bang phase detector, the phases
of the 2 signals are locked together, within the constraints of the loop
filter.
This is another false dichotomy. The aspect of the Shortt clock you are
referring to is that it is *discrete* rather than continuous. So you can
clearly see the fact that the slave oscillator is not in perfect lock step
with the master (reference). The same is true in *all* PLL circuits. The
phase of the oscillator is adjusted by the error signal. There can be no
adjustments without error, so the oscillator will not be in perfect lockstep
with the reference. It will be within some tolerance... same as the Shortt
clock. A PLL can be discrete and the phase will move in patterns with small
offsets in frequency at all times. With a continuous phase comparison the
frequency will vary continuously but still will not be "locked" to the
reference with no error. In fact, PLLs are used to remove short term jitter
from clocks by the use of a slow filter on the control signal.
--
Rick C
Jeff
2017-08-03 09:32:32 UTC
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Post by rickman
This is another false dichotomy. The aspect of the Shortt clock you are
referring to is that it is *discrete* rather than continuous.
Not correct the phases of the 2 pendulums are *never* in phase. Even
when a kick is given, as of course if they were in phase there would be
no need for a kick.
Post by rickman
So you
can clearly see the fact that the slave oscillator is not in perfect
lock step with the master (reference). The same is true in *all* PLL
circuits. The phase of the oscillator is adjusted by the error signal.
When a electronic phase lock loop is locked there is no error as the 2
signals are perfectly in phase. There will only be a change in locked
control voltage if the phase drifts.
Post by rickman
There can be no adjustments without error, so the oscillator will not be
in perfect lockstep with the reference. It will be within some
tolerance... same as the Shortt clock.
No, a phase locked loop has the same accuracy, or tolerance if you wish,
as the reference.
Post by rickman
A PLL can be discrete and the
phase will move in patterns with small offsets in frequency at all
times. With a continuous phase comparison the frequency will vary
continuously but still will not be "locked" to the reference with no
error.
No it will only vary in sympathy with the reference signal, or with
signals that are not damped by the loop filter due to being faster than
the loop filer can deal with.

Jeff
rickman
2017-08-03 15:49:00 UTC
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Post by rickman
This is another false dichotomy. The aspect of the Shortt clock you are
referring to is that it is *discrete* rather than continuous.
Not correct the phases of the 2 pendulums are *never* in phase. Even when a
kick is given, as of course if they were in phase there would be no need for
a kick.
You don't understand the meaning of "phase". If you said the two
frequencies were never the same I would agree. The slave pendulum runs
slower than the master with the intermittent impulse to adjust the phase.
The relative phase varies with time as a sawtooth function and so at some
point the phase *must* be aligned as the slave passes from being ahead to
being behind. On the next adjustment the phase is adjusted or not. When
properly adjusted the phase of the slave will only be "bumped" every other
adjustment time. On the adjustment times when the slave phase is *not*
adjusted the phase will be in alignment ideally.
Post by rickman
So you can clearly see the fact that the slave oscillator is not in
perfect lock step with the master (reference). The same is true in *all*
PLL circuits. The phase of the oscillator is adjusted by the error signal.
When a electronic phase lock loop is locked there is no error as the 2
signals are perfectly in phase. There will only be a change in locked
control voltage if the phase drifts.
You need to go back to PLL 101 class. When the PLL is "locked" it simply
means the error in phase is small enough that the loop can compensate by
varying the VCO frequency. If you understand the math you will see that
this means it will *always* hunt for the perfect alignment. If there is no
integral term in the feedback loop, there will always be a phase error
dependent on the dF/dV slope of the VCO. If there *is* an integral term in
the feedback loop the loop will have small fluctuations as the frequency
adjusts to correct the phase, but when the phase error reaches zero the
frequency error will *not* be zero and the phase error will immediately
become non-zero.
Post by rickman
There can be no adjustments without error, so the oscillator will not be
in perfect lockstep with the reference. It will be within some
tolerance... same as the Shortt clock.
No, a phase locked loop has the same accuracy, or tolerance if you wish, as
the reference.
There is always jitter in the output of the PLL that is independent of the
reference clock.
Post by rickman
A PLL can be discrete and the phase will move in patterns with small
offsets in frequency at all times. With a continuous phase comparison the
frequency will vary continuously but still will not be "locked" to the
reference with no error.
No it will only vary in sympathy with the reference signal, or with signals
that are not damped by the loop filter due to being faster than the loop
filer can deal with.
Please review your PLL materials. There is no such thing as a PLL that
aligns perfectly with the reference.
--
Rick C
Jeff
2017-08-03 17:17:37 UTC
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Post by rickman
You don't understand the meaning of "phase". If you said the two
frequencies were never the same I would agree.
Phase is fundamentally linked to frequency.
Post by rickman
The slave pendulum runs
slower than the master with the intermittent impulse to adjust the
phase. The relative phase varies with time as a sawtooth function and so
at some point the phase *must* be aligned as the slave passes from being
ahead to being behind.
That is a ridiculous statement, if it were true you could say that any 2
random signals were 'in phase' just because at some point in time they
both had the same phase angle.

Jeff
rickman
2017-08-03 17:27:04 UTC
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Post by Jeff
Post by rickman
You don't understand the meaning of "phase". If you said the two
frequencies were never the same I would agree.
Phase is fundamentally linked to frequency.
Post by rickman
The slave pendulum runs slower than the master with the intermittent
impulse to adjust the phase. The relative phase varies with time as a
sawtooth function and so at some point the phase *must* be aligned as the
slave passes from being ahead to being behind.
That is a ridiculous statement, if it were true you could say that any 2
random signals were 'in phase' just because at some point in time they both
had the same phase angle.
Not sure if you are referring to the Shortt clock or the PLL. But the
statement applies equally to both. There is no magical stability in the
PLL. It is a control loop and as such the thing being controlled will
*never* remain in phase or at the same frequency as the reference.
--
Rick C
Chris
2017-08-03 19:05:41 UTC
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Not sure if you are referring to the Shortt clock or the PLL. But the
statement applies equally to both. There is no magical stability in the
PLL. It is a control loop and as such the thing being controlled will
*never* remain in phase or at the same frequency as the reference.
I think the difference is that while a pll always has a phase offset
the reference and vco are in phase lockstep once the loop has aquired
lock. It's a closed loop system whereas the Shortt clock is an open
loop system, only getting a kick back into sync from time to time.

Like a hit and miss governor ?...

Chris
rickman
2017-08-03 21:31:05 UTC
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Post by Chris
Not sure if you are referring to the Shortt clock or the PLL. But the
statement applies equally to both. There is no magical stability in the
PLL. It is a control loop and as such the thing being controlled will
*never* remain in phase or at the same frequency as the reference.
I think the difference is that while a pll always has a phase offset
the reference and vco are in phase lockstep once the loop has aquired
lock. It's a closed loop system whereas the Shortt clock is an open
loop system, only getting a kick back into sync from time to time.
Like a hit and miss governor ?...
I don't know what you guys are seeing. The two pendulums of the Shortt
clock are in lock step. The fact that they are only compared every 30
seconds does not change the nature of the design.

The phase comparison signal from a PLL is typically "grainy" in the same way
and has to be filtered to become a control signal. The only reason you say
they are in "lock step" is because the grain is very fine. The Shortt clock
grain is very fine as well typically adjusting only every other 30 second
period.

I guess the difference is the Shortt clock is adjusting the instantaneous
phase and the average frequency while a typical PLL adjusts the
instantaneous frequency to try to keep the phase aligned. Both will see
variations in phase over time.
--
Rick C
Chris
2017-08-03 22:33:00 UTC
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I don't know what you guys are seeing. The two pendulums of the Shortt
clock are in lock step. The fact that they are only compared every 30
seconds does not change the nature of the design.
The phase comparison signal from a PLL is typically "grainy" in the same
way and has to be filtered to become a control signal. The only reason
you say they are in "lock step" is because the grain is very fine. The
Shortt clock grain is very fine as well typically adjusting only every
other 30 second period.
I guess the difference is the Shortt clock is adjusting the
instantaneous phase and the average frequency while a typical PLL
adjusts the instantaneous frequency to try to keep the phase aligned.
Both will see variations in phase over time.
I would see the Shortt clock as a frequency locked loop, not the same
thing as a pll. Different level of instantaneous precision.

Semantics, semantics :-)...

Chris
rickman
2017-08-03 22:42:04 UTC
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Post by Chris
I don't know what you guys are seeing. The two pendulums of the Shortt
clock are in lock step. The fact that they are only compared every 30
seconds does not change the nature of the design.
The phase comparison signal from a PLL is typically "grainy" in the same
way and has to be filtered to become a control signal. The only reason
you say they are in "lock step" is because the grain is very fine. The
Shortt clock grain is very fine as well typically adjusting only every
other 30 second period.
I guess the difference is the Shortt clock is adjusting the
instantaneous phase and the average frequency while a typical PLL
adjusts the instantaneous frequency to try to keep the phase aligned.
Both will see variations in phase over time.
I would see the Shortt clock as a frequency locked loop, not the same
thing as a pll. Different level of instantaneous precision.
Not sure why you say that. What is measured and adjusted is the phase.
Either the slave is a bit ahead or a bit behind and it is either spurred on
a bit or it is not. The frequency of the pendulum is not impacted other than
at the moment of phase adjustment.
--
Rick C
Jeff
2017-08-04 08:58:45 UTC
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Post by rickman
I don't know what you guys are seeing. The two pendulums of the Shortt
clock are in lock step. The fact that they are only compared every 30
seconds does not change the nature of the design.
What we are seeing is that even after the 30 second 'kick' the 2
pendulums are NOT in phase.

They may well be 'a bit closer' in phase, but the kick just moves the
difference a fixed small amount in one direction, which may be
sufficient to bring the phases closer, or it may be too much and go
through the in phase point. With the design there is no time where the 2
pendulums are *held* in phase.

The design in fact relies on the fact that the phase of the 2 pendulums
is constantly changing.

Jeff
rickman
2017-08-04 15:35:51 UTC
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Post by rickman
I don't know what you guys are seeing. The two pendulums of the Shortt
clock are in lock step. The fact that they are only compared every 30
seconds does not change the nature of the design.
What we are seeing is that even after the 30 second 'kick' the 2 pendulums
are NOT in phase.
They may well be 'a bit closer' in phase, but the kick just moves the
difference a fixed small amount in one direction, which may be sufficient to
bring the phases closer, or it may be too much and go through the in phase
point. With the design there is no time where the 2 pendulums are *held* in
phase.
The design in fact relies on the fact that the phase of the 2 pendulums is
constantly changing.
As is true for any PLL.
--
Rick C
Jeff
2017-08-05 09:45:33 UTC
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Post by rickman
What we are seeing is that even after the 30 second 'kick' the 2 pendulums
are NOT in phase.
They may well be 'a bit closer' in phase, but the kick just moves the
difference a fixed small amount in one direction, which may be sufficient to
bring the phases closer, or it may be too much and go through the in phase
point. With the design there is no time where the 2 pendulums are *held* in
phase.
The design in fact relies on the fact that the phase of the 2
pendulums is
constantly changing.
As is true for any PLL.
Rubbish, the function of a phase locked loop is to keep the phase of the
2 signals the same, within the constraints of the loop filter.

The clock *never* achieves this, it is open loop and applies a 'kick' to
one pendulum the amplitude of which is NOT related to the difference in
phase of the 2 pendulums.

A fixed kick is given without any knowledge that it will be of the
correct amplitude to achieve an in phase or near in phase condition.
There is NO feedback of an error signal that relates to the phase
difference between the 2 pendulums.

The only time phase comes into the picture is the timing of when the
'kick' is given, so as not to disrupt the normal swing of the pendulum,
and whether or not to give a kick at all.

It is and ingenious system, but not a phase locked loop.

I guess it could be closer to a PLL if the kick had its amplitude varied
by the phase difference between the 2 pendulums, but you still have the
problem that if you were in the state where no kick was required there
is no way of slowing the second pendulum without waiting for it to drift
back, so it is still open loop.

Jeff
Chris
2017-08-05 13:34:11 UTC
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Post by Jeff
Rubbish, the function of a phase locked loop is to keep the phase of the
2 signals the same, within the constraints of the loop filter.
The clock *never* achieves this, it is open loop and applies a 'kick' to
one pendulum the amplitude of which is NOT related to the difference in
phase of the 2 pendulums.
A fixed kick is given without any knowledge that it will be of the
correct amplitude to achieve an in phase or near in phase condition.
There is NO feedback of an error signal that relates to the phase
difference between the 2 pendulums.
The only time phase comes into the picture is the timing of when the
'kick' is given, so as not to disrupt the normal swing of the pendulum,
and whether or not to give a kick at all.
Exactly. The control is single path, master to slave, with no feedback
to the reference, making it an open loop design. The master has no
knowledge of the state of the slave at any time.

In a pll, there is continuous feedback from the vco to the phase
detector, closing the loop and keeping the phase offset constant,
The phase is continuously updated every cycle, whereas the Shortt
clock can have significant accumulated error in the time between
corrections...

Chris
Gareth's Downstairs Computer
2017-08-05 13:57:01 UTC
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Post by Chris
Exactly. The control is single path, master to slave, with no feedback
to the reference, making it an open loop design. The master has no
knowledge of the state of the slave at any time.
Untrue.

The matter starts off when the slave signals to the master and drops
the gravity link in the master, then, when the master pendulum is in
a position to accept the impulse from that dropped gravity link, it
signals back to the slave

But ... I'm still trying to google for the exact mechanisms because
most URLs only hint at what is happening. (I'm also awaiting delivery
of a couple of hope-jones' books about electric clocks)
mm0fmf
2017-08-05 14:14:18 UTC
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Post by Gareth's Downstairs Computer
Post by Chris
Exactly. The control is single path, master to slave, with no feedback
to the reference, making it an open loop design. The master has no
knowledge of the state of the slave at any time.
Untrue.
The matter starts off when the slave signals to the master and drops
the gravity link in the master, then, when the master pendulum is in
a position to accept the impulse from that dropped gravity link, it
signals back to the slave
But ... I'm still trying to google for the exact mechanisms because
most URLs only hint at what is happening. (I'm also awaiting delivery
of a couple of hope-jones' books about electric clocks)
I hope you have more success getting a copy of those books than getting
the PA tuning instructions for a mass produced amateur TX.
Bernie
2017-08-05 14:54:48 UTC
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On Sat, 5 Aug 2017 14:57:01 +0100
Gareth's Downstairs Computer
Post by Gareth's Downstairs Computer
But ... I'm still trying to google for the exact mechanisms because
most URLs only hint at what is happening. (I'm also awaiting delivery
of a couple of hope-jones' books about electric clocks)
Horological Journal 139/3 Accurate Rating of Clocks & Watches. Shortt
Clock

www.ebay.co.uk/itm/141115584188
rickman
2017-08-05 15:08:55 UTC
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Post by Gareth's Downstairs Computer
Post by Chris
Exactly. The control is single path, master to slave, with no feedback
to the reference, making it an open loop design. The master has no
knowledge of the state of the slave at any time.
Untrue.
The matter starts off when the slave signals to the master and drops
the gravity link in the master, then, when the master pendulum is in
a position to accept the impulse from that dropped gravity link, it
signals back to the slave
But ... I'm still trying to google for the exact mechanisms because
most URLs only hint at what is happening. (I'm also awaiting delivery
of a couple of hope-jones' books about electric clocks)
What you are describing is how the phase measurement of the master is made.
The gravity lever is simply a remontoire providing a consistent push to
overcome the force of friction. It is designed to be invariant of small
changes in timing of its release. You can see that in the animation linked
below. The gravity arm is released at the point when the wheel is directly
under the end of the gravity lever. A small change in timing changes the
force only a tiny amount. This is critical to maintaining the swing of the
free pendulum without affecting its period.

http://www.chronometrophilia.ch/Electric-clocks/Shortt.htm

The animation happens in real time so it is hard to see the details of what
is going on. The gravity lever and accompanying control is the magic of the
clock. The rest is pretty straight forward. You need Flash to view this
page. There is a button to see the wires.
--
Rick C
rickman
2017-08-05 16:10:02 UTC
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Post by rickman
Post by Gareth's Downstairs Computer
Post by Chris
Exactly. The control is single path, master to slave, with no feedback
to the reference, making it an open loop design. The master has no
knowledge of the state of the slave at any time.
Untrue.
The matter starts off when the slave signals to the master and drops
the gravity link in the master, then, when the master pendulum is in
a position to accept the impulse from that dropped gravity link, it
signals back to the slave
But ... I'm still trying to google for the exact mechanisms because
most URLs only hint at what is happening. (I'm also awaiting delivery
of a couple of hope-jones' books about electric clocks)
What you are describing is how the phase measurement of the master is made.
The gravity lever is simply a remontoire providing a consistent push to
overcome the force of friction. It is designed to be invariant of small
changes in timing of its release. You can see that in the animation linked
below. The gravity arm is released at the point when the wheel is directly
under the end of the gravity lever. A small change in timing changes the
force only a tiny amount. This is critical to maintaining the swing of the
free pendulum without affecting its period.
http://www.chronometrophilia.ch/Electric-clocks/Shortt.htm
The animation happens in real time so it is hard to see the details of what
is going on. The gravity lever and accompanying control is the magic of the
clock. The rest is pretty straight forward. You need Flash to view this
page. There is a button to see the wires.
One other part of the Shortt clock that requires careful thought is the
relay and spring that perform the phase detection and correction. The slave
pendulum has a leaf spring parallel to the rod and the control relay has a
pick which is activated under control of the master gravity lever. The pick
can intercept the leaf spring or not, depending on the timing. There is an
issue with this which is impossible to eliminate, only minimize and that is
metastability. A decision is being made and it can not be done with
infinite resolution. So the pick and leaf spring must be designed to
minimize the problem, likely done by making the spring thin as possible and
making the edge on the pick as sharp as possible.

We see the same problem in electronics when trying to make decisions on the
state of an input that is changing.
--
Rick C
rickman
2017-08-05 14:48:53 UTC
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Post by Chris
Post by Jeff
Rubbish, the function of a phase locked loop is to keep the phase of the
2 signals the same, within the constraints of the loop filter.
The clock *never* achieves this, it is open loop and applies a 'kick' to
one pendulum the amplitude of which is NOT related to the difference in
phase of the 2 pendulums.
A fixed kick is given without any knowledge that it will be of the
correct amplitude to achieve an in phase or near in phase condition.
There is NO feedback of an error signal that relates to the phase
difference between the 2 pendulums.
The only time phase comes into the picture is the timing of when the
'kick' is given, so as not to disrupt the normal swing of the pendulum,
and whether or not to give a kick at all.
Exactly. The control is single path, master to slave, with no feedback
to the reference, making it an open loop design. The master has no
knowledge of the state of the slave at any time.
You aren't making sense. The reference is never adjusted in a PLL. That's
why it's the *reference*.
Post by Chris
In a pll, there is continuous feedback from the vco to the phase
detector, closing the loop and keeping the phase offset constant,
The phase is continuously updated every cycle, whereas the Shortt
clock can have significant accumulated error in the time between
corrections...
There is no requirement in a PLL for continuous action or even frequent
action.
--
Rick C
Chris
2017-08-05 18:33:41 UTC
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You aren't making sense. The reference is never adjusted in a PLL.
That's why it's the *reference*.
Just where did I say that ?. Having worked with pll's since the
4046 and earlier, I should know the difference.
Post by Chris
In a pll, there is continuous feedback from the vco to the phase
detector, closing the loop and keeping the phase offset constant,
The phase is continuously updated every cycle, whereas the Shortt
clock can have significant accumulated error in the time between
corrections...
There is no requirement in a PLL for continuous action or even frequent
action.
That's probably why the Shortt clock is described as a hit and miss
system and correction is unipolar, whereas a classic pll continually
updates the vco every cycle, not multiples thereof.

Ok, the Shortt clock is probably as close as you can get to a classic
pll using mechanics :-)...

Chris
rickman
2017-08-05 19:06:12 UTC
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Post by Chris
You aren't making sense. The reference is never adjusted in a PLL.
That's why it's the *reference*.
Just where did I say that ?. Having worked with pll's since the
4046 and earlier, I should know the difference.
You snipped the part I was replying to but you talked about the master
knowing the status of the slave which would only be useful if you were
adjusting the master.
Post by Chris
Post by Chris
In a pll, there is continuous feedback from the vco to the phase
detector, closing the loop and keeping the phase offset constant,
The phase is continuously updated every cycle, whereas the Shortt
clock can have significant accumulated error in the time between
corrections...
There is no requirement in a PLL for continuous action or even frequent
action.
That's probably why the Shortt clock is described as a hit and miss
system and correction is unipolar, whereas a classic pll continually
updates the vco every cycle, not multiples thereof.
"Classic"??? There is no such definition of a PLL to "continuously" update
anything.
Post by Chris
Ok, the Shortt clock is probably as close as you can get to a classic
pll using mechanics :-)...
Yes, because it *is* a PLL. In fact the problem most people have with it is
that it doesn't adjust the phase by adjusting the frequency of the slave.
It adjusts the *phase* so clearly it *is* a phase locked loop.
--
Rick C
Gareth's Downstairs Computer
2017-08-05 19:14:56 UTC
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Post by rickman
Yes, because it *is* a PLL. In fact the problem most people have with
it is that it doesn't adjust the phase by adjusting the frequency of the
slave. It adjusts the *phase* so clearly it *is* a phase locked loop.
All pendulums have circular error where the frequency is determined by
the amplitude of swing, so for the half cycle where the phase is
adjusted by abridging the swing by the hit of the hit and miss
stabiliser, the frequency of the slave is, indeed, changed.

The standard formula given for the cycle time of pendulums ..

2 * PI * root( L / G)

... is only valid for those small angles where sin( theta ) = theta,
and such angles are so infinitesimal that no visible movement
of a pendulum would be seen!
Chris
2017-08-05 20:06:56 UTC
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Post by Gareth's Downstairs Computer
Yes, because it *is* a PLL. In fact the problem most people have with
it is that it doesn't adjust the phase by adjusting the frequency of
the slave. It adjusts the *phase* so clearly it *is* a phase locked loop.
All pendulums have circular error where the frequency is determined by
the amplitude of swing, so for the half cycle where the phase is
adjusted by abridging the swing by the hit of the hit and miss
stabiliser, the frequency of the slave is, indeed, changed.
The standard formula given for the cycle time of pendulums ..
2 * PI * root( L / G)
... is only valid for those small angles where sin( theta ) = theta,
and such angles are so infinitesimal that no visible movement
of a pendulum would be seen!
This just won't go away, will it :-). Here we are, arguing over the
semantics of phase locked loops, but the term pll didn't come into
wide use until the 1960's, decades after the Shortt clock. I'll
continue to think of it as a hit and miss governor, as it was
originally described...

Chris
rickman
2017-08-05 21:26:25 UTC
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Post by Chris
Post by Gareth's Downstairs Computer
Yes, because it *is* a PLL. In fact the problem most people have with
it is that it doesn't adjust the phase by adjusting the frequency of
the slave. It adjusts the *phase* so clearly it *is* a phase locked loop.
All pendulums have circular error where the frequency is determined by
the amplitude of swing, so for the half cycle where the phase is
adjusted by abridging the swing by the hit of the hit and miss
stabiliser, the frequency of the slave is, indeed, changed.
The standard formula given for the cycle time of pendulums ..
2 * PI * root( L / G)
... is only valid for those small angles where sin( theta ) = theta,
and such angles are so infinitesimal that no visible movement
of a pendulum would be seen!
This just won't go away, will it :-). Here we are, arguing over the
semantics of phase locked loops, but the term pll didn't come into
wide use until the 1960's, decades after the Shortt clock. I'll
continue to think of it as a hit and miss governor, as it was
originally described...
And that is what it is, not at all unlike a PLL using a bang-bang phase
detector.
--
Rick C
Brian Reay
2017-08-05 21:10:06 UTC
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Post by Gareth's Downstairs Computer
Post by rickman
Yes, because it *is* a PLL. In fact the problem most people have with
it is that it doesn't adjust the phase by adjusting the frequency of
the slave. It adjusts the *phase* so clearly it *is* a phase locked loop.
All pendulums have circular error where the frequency is determined by
the amplitude of swing, so for the half cycle where the phase is
adjusted by abridging the swing by the hit of the hit and miss
stabiliser, the frequency of the slave is, indeed, changed.
The standard formula given for the cycle time of pendulums ..
2 * PI * root( L / G)
... is only valid for those small angles where sin( theta ) = theta,
and such angles are so infinitesimal that no visible movement
of a pendulum would be seen!
You seem to be confusing two different things

The error you refer to is due to the pendulum not actually taking a
direct line between the ends of its travel, the error is small for small
amplitudes. There was a famous experiment by a Frenchman in, I think
Paris, he hung a huge pendulum and let it trace its path in sand, rather
than it going 'to and fro' it actually went in arcs as it went to and fro.

The effect is minimised by reducing the amplitude.

As you correctly say, the frequency of a pendulum is given by the
formula you state. If you 'give it a nudge' you may shorted one swing
but the overall frequency is still determined by the formula.

The 'nudge' will change the phase of the swing, not the frequency- ie it
will shorten one cycle.
rickman
2017-08-05 21:42:10 UTC
Permalink
Raw Message
Post by Brian Reay
Post by Gareth's Downstairs Computer
Post by rickman
Yes, because it *is* a PLL. In fact the problem most people have with it
is that it doesn't adjust the phase by adjusting the frequency of the
slave. It adjusts the *phase* so clearly it *is* a phase locked loop.
All pendulums have circular error where the frequency is determined by
the amplitude of swing, so for the half cycle where the phase is adjusted
by abridging the swing by the hit of the hit and miss stabiliser, the
frequency of the slave is, indeed, changed.
The standard formula given for the cycle time of pendulums ..
2 * PI * root( L / G)
... is only valid for those small angles where sin( theta ) = theta,
and such angles are so infinitesimal that no visible movement
of a pendulum would be seen!
You seem to be confusing two different things
The error you refer to is due to the pendulum not actually taking a direct
line between the ends of its travel, the error is small for small
amplitudes. There was a famous experiment by a Frenchman in, I think Paris,
he hung a huge pendulum and let it trace its path in sand, rather than it
going 'to and fro' it actually went in arcs as it went to and fro.
The effect is minimised by reducing the amplitude.
I believe you are thinking of the Foucault pendulum. This had nothing to do
with elliptical paths of pendulums. This was a pendulum free to swing along
any axis. As the earth rotates the pendulum continues to swing in its
original path and the earth turns beneath it. Of course the pendulum
appears to rotate the plane of swing.
Post by Brian Reay
As you correctly say, the frequency of a pendulum is given by the formula
you state. If you 'give it a nudge' you may shorted one swing but the
overall frequency is still determined by the formula.
The 'nudge' will change the phase of the swing, not the frequency- ie it
will shorten one cycle.
Yes, that is right. The change in frequency (phase change rate) is only
momentary.
--
Rick C
rickman
2017-08-05 21:24:41 UTC
Permalink
Raw Message
Post by Gareth's Downstairs Computer
Post by rickman
Yes, because it *is* a PLL. In fact the problem most people have with it
is that it doesn't adjust the phase by adjusting the frequency of the
slave. It adjusts the *phase* so clearly it *is* a phase locked loop.
All pendulums have circular error where the frequency is determined by
the amplitude of swing,
All *uncorrected* pendulums have circular error. The Fedchenko clock has a
mounting spring for the pendulum that corrects for circular error.
Post by Gareth's Downstairs Computer
so for the half cycle where the phase is adjusted by
abridging the swing by the hit of the hit and miss stabiliser, the frequency
of the slave is, indeed, changed.
This has nothing to do with the circular error.
Post by Gareth's Downstairs Computer
The standard formula given for the cycle time of pendulums ..
2 * PI * root( L / G)
... is only valid for those small angles where sin( theta ) = theta,
and such angles are so infinitesimal that no visible movement
of a pendulum would be seen!
This equation is an approximation which ignores the higher terms of the
power series of the full equation. It is only truly valid for no swing at all.
--
Rick C
Gareth's Downstairs Computer
2017-08-05 21:57:25 UTC
Permalink
Raw Message
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
Yes, because it *is* a PLL. In fact the problem most people have with it
is that it doesn't adjust the phase by adjusting the frequency of the
slave. It adjusts the *phase* so clearly it *is* a phase locked loop.
All pendulums have circular error where the frequency is determined by
the amplitude of swing,
All *uncorrected* pendulums have circular error. The Fedchenko clock
has a mounting spring for the pendulum that corrects for circular error.
Hadn't heard of that one. At the BHI lecture there was mention of
another correction of circular error by a colied spring attached
somewhere at the bottom, but I wasn't paying full attention at
that point.

There were also other means such as cycloidal cheeks around the
suspension spring.
Post by rickman
Post by Gareth's Downstairs Computer
so for the half cycle where the phase is adjusted by
abridging the swing by the hit of the hit and miss stabiliser, the frequency
of the slave is, indeed, changed.
This has nothing to do with the circular error.
It has everything to do with the circular error and the variation
in frequency that comes with varying amplitude of the swing.
Post by rickman
Post by Gareth's Downstairs Computer
The standard formula given for the cycle time of pendulums ..
2 * PI * root( L / G)
... is only valid for those small angles where sin( theta ) = theta,
and such angles are so infinitesimal that no visible movement
of a pendulum would be seen!
This equation is an approximation which ignores the higher terms of the
power series of the full equation. It is only truly valid for no swing at all.
... which is virtually the range where sin( theta) = theta.
rickman
2017-08-05 22:25:51 UTC
Permalink
Raw Message
Post by Gareth's Downstairs Computer
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
Yes, because it *is* a PLL. In fact the problem most people have with it
is that it doesn't adjust the phase by adjusting the frequency of the
slave. It adjusts the *phase* so clearly it *is* a phase locked loop.
All pendulums have circular error where the frequency is determined by
the amplitude of swing,
All *uncorrected* pendulums have circular error. The Fedchenko clock has
a mounting spring for the pendulum that corrects for circular error.
Hadn't heard of that one. At the BHI lecture there was mention of
another correction of circular error by a colied spring attached
somewhere at the bottom, but I wasn't paying full attention at
that point.
There were also other means such as cycloidal cheeks around the
suspension spring.
Post by rickman
Post by Gareth's Downstairs Computer
so for the half cycle where the phase is adjusted by
abridging the swing by the hit of the hit and miss stabiliser, the frequency
of the slave is, indeed, changed.
This has nothing to do with the circular error.
It has everything to do with the circular error and the variation
in frequency that comes with varying amplitude of the swing.
You seem to be completely misunderstanding the operation of the Shortt
clock. The slave pendulum has no need for correction of circular error. It
is a good pendulum, but not a great one. It doesn't need to be great, it is
corrected every 30 seconds by the electromechanical escapement of the master
pendulum. It only has to be good enough to provide an appropriately timed
release of the gravity lever.

So the small circular error has no bearing on the slave pendulum.
Post by Gareth's Downstairs Computer
Post by rickman
Post by Gareth's Downstairs Computer
The standard formula given for the cycle time of pendulums ..
2 * PI * root( L / G)
... is only valid for those small angles where sin( theta ) = theta,
and such angles are so infinitesimal that no visible movement
of a pendulum would be seen!
This equation is an approximation which ignores the higher terms of the
power series of the full equation. It is only truly valid for no swing at all.
... which is virtually the range where sin( theta) = theta.
Exactly. This *is* the range where sin(theta) = theta. Anywhere other than
zero it is an approximation.
--
Rick C
Gareth's Downstairs Computer
2017-08-06 09:26:41 UTC
Permalink
Raw Message
Post by rickman
You seem to be completely misunderstanding the operation of the Shortt
clock. The slave pendulum has no need for correction of circular
error.
I'm sorry, but you totally misunderstood what I was saying, which was
that because all pendulums exhibit circular error, when the hit occurs
in the hit and miss synchroniser and foreshortens the swing, then, for
that half-cycle, and only that half cycle, the frequency is
changed, as it must be.

Just as in the electronic PLL, instantaneous changes of phase have
instantaneous changes of frequency, no matter how short lived,
associated with them.
rickman
2017-08-06 16:18:53 UTC
Permalink
Raw Message
Post by Gareth's Downstairs Computer
Post by rickman
You seem to be completely misunderstanding the operation of the Shortt
clock. The slave pendulum has no need for correction of circular error.
I'm sorry, but you totally misunderstood what I was saying, which was
that because all pendulums exhibit circular error, when the hit occurs
in the hit and miss synchroniser and foreshortens the swing, then, for
that half-cycle, and only that half cycle, the frequency is
changed, as it must be.
Just as in the electronic PLL, instantaneous changes of phase have
instantaneous changes of frequency, no matter how short lived,
associated with them.
What you say about frequency vs. phase is true and how the Shortt clock
adjusts phase, but it has nothing to do with circular error of the pendulum.
The correction of the phase is from the added spring resistance shortening
the time as well as the travel of the pendulum. The fact that the swing is
shorter and the second order circular error will create a tiny error in the
timing is pretty much irrelevant. The real change is from the added spring
constant changing the first order effect in the pendulum equation. The
coefficient of the gravitational constant is effectively changed by the spring.

Is that more clear?
--
Rick C
Gareth's Downstairs Computer
2017-08-06 17:37:33 UTC
Permalink
Raw Message
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
You seem to be completely misunderstanding the operation of the Shortt
clock. The slave pendulum has no need for correction of circular error.
I'm sorry, but you totally misunderstood what I was saying, which was
that because all pendulums exhibit circular error, when the hit occurs
in the hit and miss synchroniser and foreshortens the swing, then, for
that half-cycle, and only that half cycle, the frequency is
changed, as it must be.
Just as in the electronic PLL, instantaneous changes of phase have
instantaneous changes of frequency, no matter how short lived,
associated with them.
What you say about frequency vs. phase is true and how the Shortt clock
adjusts phase, but it has nothing to do with circular error of the
pendulum. The correction of the phase is from the added spring
resistance shortening the time as well as the travel of the pendulum.
The fact that the swing is shorter and the second order circular error
will create a tiny error in the timing is pretty much irrelevant. The
real change is from the added spring constant changing the first order
effect in the pendulum equation. The coefficient of the gravitational
constant is effectively changed by the spring.
Is that more clear?
You continue to misunderstand. Any pendulum swinging with circular error
speeds up for shorter amplitude; speeding up means increased frequency.
Therefore, for the half cycle inwhich there is a hit, a shorter
amplitude and hence instantaneous higher frequency exists.
rickman
2017-08-06 17:52:19 UTC
Permalink
Raw Message
Post by Gareth's Downstairs Computer
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
You seem to be completely misunderstanding the operation of the Shortt
clock. The slave pendulum has no need for correction of circular error.
I'm sorry, but you totally misunderstood what I was saying, which was
that because all pendulums exhibit circular error, when the hit occurs
in the hit and miss synchroniser and foreshortens the swing, then, for
that half-cycle, and only that half cycle, the frequency is
changed, as it must be.
Just as in the electronic PLL, instantaneous changes of phase have
instantaneous changes of frequency, no matter how short lived,
associated with them.
What you say about frequency vs. phase is true and how the Shortt clock
adjusts phase, but it has nothing to do with circular error of the
pendulum. The correction of the phase is from the added spring resistance
shortening the time as well as the travel of the pendulum. The fact that
the swing is shorter and the second order circular error will create a
tiny error in the timing is pretty much irrelevant. The real change is
from the added spring constant changing the first order effect in the
pendulum equation. The coefficient of the gravitational constant is
effectively changed by the spring.
Is that more clear?
You continue to misunderstand. Any pendulum swinging with circular error
speeds up for shorter amplitude; speeding up means increased frequency.
Therefore, for the half cycle inwhich there is a hit, a shorter amplitude
and hence instantaneous higher frequency exists.
I understand perfectly and explained it for you in excruciating detail. The
change in phase of the Shortt clock slave pendulum is due to the FIRST ORDER
change in the effective gravitational constant in the pendulum equation by
engaging the leaf spring. While the reduced amplitude of the swing *will*
cause a SECOND ORDER effect in the motion of the pendulum, it will be MUCH
SMALLER than the FIRST ORDER effect.

What part of this do you not understand or not agree with?
--
Rick C
Gareth's Downstairs Computer
2017-08-06 18:15:02 UTC
Permalink
Raw Message
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
You seem to be completely misunderstanding the operation of the Shortt
clock. The slave pendulum has no need for correction of circular error.
I'm sorry, but you totally misunderstood what I was saying, which was
that because all pendulums exhibit circular error, when the hit occurs
in the hit and miss synchroniser and foreshortens the swing, then, for
that half-cycle, and only that half cycle, the frequency is
changed, as it must be.
Just as in the electronic PLL, instantaneous changes of phase have
instantaneous changes of frequency, no matter how short lived,
associated with them.
What you say about frequency vs. phase is true and how the Shortt clock
adjusts phase, but it has nothing to do with circular error of the
pendulum. The correction of the phase is from the added spring resistance
shortening the time as well as the travel of the pendulum. The fact that
the swing is shorter and the second order circular error will create a
tiny error in the timing is pretty much irrelevant. The real change is
from the added spring constant changing the first order effect in the
pendulum equation. The coefficient of the gravitational constant is
effectively changed by the spring.
Is that more clear?
You continue to misunderstand. Any pendulum swinging with circular error
speeds up for shorter amplitude; speeding up means increased frequency.
Therefore, for the half cycle inwhich there is a hit, a shorter amplitude
and hence instantaneous higher frequency exists.
I understand perfectly and explained it for you in excruciating detail.
The change in phase of the Shortt clock slave pendulum is due to the
FIRST ORDER change in the effective gravitational constant in the
pendulum equation by engaging the leaf spring. While the reduced
amplitude of the swing *will* cause a SECOND ORDER effect in the motion
of the pendulum, it will be MUCH SMALLER than the FIRST ORDER effect.
What part of this do you not understand or not agree with?
It's not that I do not understand nor disagree with you, it's that
you're off on a complete tangent to what I was suggesting, and
do not realise it.
Brian Reay
2017-08-06 18:16:40 UTC
Permalink
Raw Message
Post by Gareth's Downstairs Computer
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
You seem to be completely misunderstanding the operation of the Shortt
clock. The slave pendulum has no need for correction of circular error.
I'm sorry, but you totally misunderstood what I was saying, which was
that because all pendulums exhibit circular error, when the hit occurs
in the hit and miss synchroniser and foreshortens the swing, then, for
that half-cycle, and only that half cycle, the frequency is
changed, as it must be.
Just as in the electronic PLL, instantaneous changes of phase have
instantaneous changes of frequency, no matter how short lived,
associated with them.
What you say about frequency vs. phase is true and how the Shortt clock
adjusts phase, but it has nothing to do with circular error of the
pendulum. The correction of the phase is from the added spring resistance
shortening the time as well as the travel of the pendulum. The fact that
the swing is shorter and the second order circular error will create a
tiny error in the timing is pretty much irrelevant. The real change is
from the added spring constant changing the first order effect in the
pendulum equation. The coefficient of the gravitational constant is
effectively changed by the spring.
Is that more clear?
You continue to misunderstand. Any pendulum swinging with circular error
speeds up for shorter amplitude; speeding up means increased frequency.
Therefore, for the half cycle inwhich there is a hit, a shorter amplitude
and hence instantaneous higher frequency exists.
I understand perfectly and explained it for you in excruciating
detail. The change in phase of the Shortt clock slave pendulum is due
to the FIRST ORDER change in the effective gravitational constant in
the pendulum equation by engaging the leaf spring. While the reduced
amplitude of the swing *will* cause a SECOND ORDER effect in the
motion of the pendulum, it will be MUCH SMALLER than the FIRST ORDER
effect.
What part of this do you not understand or not agree with?
It's not that I do not understand nor disagree with you, it's that
you're off on a complete tangent to what I was suggesting, and
do not realise it.
No he isn't, you are not keeping up.
mm0fmf
2017-08-06 18:56:12 UTC
Permalink
Raw Message
Post by Brian Reay
Post by Gareth's Downstairs Computer
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
You seem to be completely misunderstanding the operation of the Shortt
clock. The slave pendulum has no need for correction of circular error.
I'm sorry, but you totally misunderstood what I was saying, which was
that because all pendulums exhibit circular error, when the hit occurs
in the hit and miss synchroniser and foreshortens the swing, then, for
that half-cycle, and only that half cycle, the frequency is
changed, as it must be.
Just as in the electronic PLL, instantaneous changes of phase have
instantaneous changes of frequency, no matter how short lived,
associated with them.
What you say about frequency vs. phase is true and how the Shortt clock
adjusts phase, but it has nothing to do with circular error of the
pendulum. The correction of the phase is from the added spring resistance
shortening the time as well as the travel of the pendulum. The fact that
the swing is shorter and the second order circular error will create a
tiny error in the timing is pretty much irrelevant. The real change is
from the added spring constant changing the first order effect in the
pendulum equation. The coefficient of the gravitational constant is
effectively changed by the spring.
Is that more clear?
You continue to misunderstand. Any pendulum swinging with circular error
speeds up for shorter amplitude; speeding up means increased frequency.
Therefore, for the half cycle inwhich there is a hit, a shorter amplitude
and hence instantaneous higher frequency exists.
I understand perfectly and explained it for you in excruciating
detail. The change in phase of the Shortt clock slave pendulum is due
to the FIRST ORDER change in the effective gravitational constant in
the pendulum equation by engaging the leaf spring. While the reduced
amplitude of the swing *will* cause a SECOND ORDER effect in the
motion of the pendulum, it will be MUCH SMALLER than the FIRST ORDER
effect.
What part of this do you not understand or not agree with?
It's not that I do not understand nor disagree with you, it's that
you're off on a complete tangent to what I was suggesting, and
do not realise it.
No he isn't, you are not keeping up.
If he's not keeping up then he needs Viagra.
Stephen Thomas Cole
2017-08-06 18:57:35 UTC
Permalink
Raw Message
Post by mm0fmf
Post by Brian Reay
Post by Gareth's Downstairs Computer
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
You seem to be completely misunderstanding the operation of the Shortt
clock. The slave pendulum has no need for correction of circular error.
I'm sorry, but you totally misunderstood what I was saying, which was
that because all pendulums exhibit circular error, when the hit occurs
in the hit and miss synchroniser and foreshortens the swing, then, for
that half-cycle, and only that half cycle, the frequency is
changed, as it must be.
Just as in the electronic PLL, instantaneous changes of phase have
instantaneous changes of frequency, no matter how short lived,
associated with them.
What you say about frequency vs. phase is true and how the Shortt clock
adjusts phase, but it has nothing to do with circular error of the
pendulum. The correction of the phase is from the added spring resistance
shortening the time as well as the travel of the pendulum. The fact that
the swing is shorter and the second order circular error will create a
tiny error in the timing is pretty much irrelevant. The real change is
from the added spring constant changing the first order effect in the
pendulum equation. The coefficient of the gravitational constant is
effectively changed by the spring.
Is that more clear?
You continue to misunderstand. Any pendulum swinging with circular error
speeds up for shorter amplitude; speeding up means increased frequency.
Therefore, for the half cycle inwhich there is a hit, a shorter amplitude
and hence instantaneous higher frequency exists.
I understand perfectly and explained it for you in excruciating
detail. The change in phase of the Shortt clock slave pendulum is due
to the FIRST ORDER change in the effective gravitational constant in
the pendulum equation by engaging the leaf spring. While the reduced
amplitude of the swing *will* cause a SECOND ORDER effect in the
motion of the pendulum, it will be MUCH SMALLER than the FIRST ORDER
effect.
What part of this do you not understand or not agree with?
It's not that I do not understand nor disagree with you, it's that
you're off on a complete tangent to what I was suggesting, and
do not realise it.
No he isn't, you are not keeping up.
If he's not keeping up then he needs Viagra.
I expect that Mrs Evans has been putting bromide in his tea since shortly
after they got married.
--
STC / M0TEY /
http://twitter.com/ukradioamateur
rickman
2017-08-06 21:15:59 UTC
Permalink
Raw Message
Post by Gareth's Downstairs Computer
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
You seem to be completely misunderstanding the operation of the Shortt
clock. The slave pendulum has no need for correction of circular error.
I'm sorry, but you totally misunderstood what I was saying, which was
that because all pendulums exhibit circular error, when the hit occurs
in the hit and miss synchroniser and foreshortens the swing, then, for
that half-cycle, and only that half cycle, the frequency is
changed, as it must be.
Just as in the electronic PLL, instantaneous changes of phase have
instantaneous changes of frequency, no matter how short lived,
associated with them.
What you say about frequency vs. phase is true and how the Shortt clock
adjusts phase, but it has nothing to do with circular error of the
pendulum. The correction of the phase is from the added spring resistance
shortening the time as well as the travel of the pendulum. The fact that
the swing is shorter and the second order circular error will create a
tiny error in the timing is pretty much irrelevant. The real change is
from the added spring constant changing the first order effect in the
pendulum equation. The coefficient of the gravitational constant is
effectively changed by the spring.
Is that more clear?
You continue to misunderstand. Any pendulum swinging with circular error
speeds up for shorter amplitude; speeding up means increased frequency.
Therefore, for the half cycle inwhich there is a hit, a shorter amplitude
and hence instantaneous higher frequency exists.
I understand perfectly and explained it for you in excruciating detail.
The change in phase of the Shortt clock slave pendulum is due to the FIRST
ORDER change in the effective gravitational constant in the pendulum
equation by engaging the leaf spring. While the reduced amplitude of the
swing *will* cause a SECOND ORDER effect in the motion of the pendulum, it
will be MUCH SMALLER than the FIRST ORDER effect.
What part of this do you not understand or not agree with?
It's not that I do not understand nor disagree with you, it's that
you're off on a complete tangent to what I was suggesting, and
do not realise it.
Sorry, I was talking about how the Shortt clock adjusts the timing of the
slave pendulum. What are you talking about?
--
Rick C
Brian Reay
2017-08-06 21:56:41 UTC
Permalink
Raw Message
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
You seem to be completely misunderstanding the operation of the Shortt
clock. The slave pendulum has no need for correction of circular error.
I'm sorry, but you totally misunderstood what I was saying, which was
that because all pendulums exhibit circular error, when the hit occurs
in the hit and miss synchroniser and foreshortens the swing, then, for
that half-cycle, and only that half cycle, the frequency is
changed, as it must be.
Just as in the electronic PLL, instantaneous changes of phase have
instantaneous changes of frequency, no matter how short lived,
associated with them.
What you say about frequency vs. phase is true and how the Shortt clock
adjusts phase, but it has nothing to do with circular error of the
pendulum. The correction of the phase is from the added spring resistance
shortening the time as well as the travel of the pendulum. The fact that
the swing is shorter and the second order circular error will create a
tiny error in the timing is pretty much irrelevant. The real change is
from the added spring constant changing the first order effect in the
pendulum equation. The coefficient of the gravitational constant is
effectively changed by the spring.
Is that more clear?
You continue to misunderstand. Any pendulum swinging with circular error
speeds up for shorter amplitude; speeding up means increased frequency.
Therefore, for the half cycle inwhich there is a hit, a shorter amplitude
and hence instantaneous higher frequency exists.
I understand perfectly and explained it for you in excruciating detail.
The change in phase of the Shortt clock slave pendulum is due to the FIRST
ORDER change in the effective gravitational constant in the pendulum
equation by engaging the leaf spring. While the reduced amplitude of the
swing *will* cause a SECOND ORDER effect in the motion of the pendulum, it
will be MUCH SMALLER than the FIRST ORDER effect.
What part of this do you not understand or not agree with?
It's not that I do not understand nor disagree with you, it's that
you're off on a complete tangent to what I was suggesting, and
do not realise it.
Sorry, I was talking about how the Shortt clock adjusts the timing of
the slave pendulum. What are you talking about?
This is one of Evans' usual tactics Rick, he is out of his depth so he
is trying to muddy the water. Before long he will be hurling abuse in
earnest.
Gareth's Downstairs Computer
2017-08-06 22:10:40 UTC
Permalink
Raw Message
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
You seem to be completely misunderstanding the operation of the Shortt
clock. The slave pendulum has no need for correction of circular error.
I'm sorry, but you totally misunderstood what I was saying, which was
that because all pendulums exhibit circular error, when the hit occurs
in the hit and miss synchroniser and foreshortens the swing, then, for
that half-cycle, and only that half cycle, the frequency is
changed, as it must be.
Just as in the electronic PLL, instantaneous changes of phase have
instantaneous changes of frequency, no matter how short lived,
associated with them.
What you say about frequency vs. phase is true and how the Shortt clock
adjusts phase, but it has nothing to do with circular error of the
pendulum. The correction of the phase is from the added spring resistance
shortening the time as well as the travel of the pendulum. The fact that
the swing is shorter and the second order circular error will create a
tiny error in the timing is pretty much irrelevant. The real change is
from the added spring constant changing the first order effect in the
pendulum equation. The coefficient of the gravitational constant is
effectively changed by the spring.
Is that more clear?
You continue to misunderstand. Any pendulum swinging with circular error
speeds up for shorter amplitude; speeding up means increased frequency.
Therefore, for the half cycle inwhich there is a hit, a shorter amplitude
and hence instantaneous higher frequency exists.
I understand perfectly and explained it for you in excruciating detail.
The change in phase of the Shortt clock slave pendulum is due to the FIRST
ORDER change in the effective gravitational constant in the pendulum
equation by engaging the leaf spring. While the reduced amplitude of the
swing *will* cause a SECOND ORDER effect in the motion of the pendulum, it
will be MUCH SMALLER than the FIRST ORDER effect.
What part of this do you not understand or not agree with?
It's not that I do not understand nor disagree with you, it's that
you're off on a complete tangent to what I was suggesting, and
do not realise it.
Sorry, I was talking about how the Shortt clock adjusts the timing of
the slave pendulum. What are you talking about?
I ... explained it for you in excruciating detail.
rickman
2017-08-06 23:58:25 UTC
Permalink
Raw Message
Post by Gareth's Downstairs Computer
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
You seem to be completely misunderstanding the operation of the Shortt
clock. The slave pendulum has no need for correction of circular error.
I'm sorry, but you totally misunderstood what I was saying, which was
that because all pendulums exhibit circular error, when the hit occurs
in the hit and miss synchroniser and foreshortens the swing, then, for
that half-cycle, and only that half cycle, the frequency is
changed, as it must be.
Just as in the electronic PLL, instantaneous changes of phase have
instantaneous changes of frequency, no matter how short lived,
associated with them.
What you say about frequency vs. phase is true and how the Shortt clock
adjusts phase, but it has nothing to do with circular error of the
pendulum. The correction of the phase is from the added spring resistance
shortening the time as well as the travel of the pendulum. The fact that
the swing is shorter and the second order circular error will create a
tiny error in the timing is pretty much irrelevant. The real change is
from the added spring constant changing the first order effect in the
pendulum equation. The coefficient of the gravitational constant is
effectively changed by the spring.
Is that more clear?
You continue to misunderstand. Any pendulum swinging with circular error
speeds up for shorter amplitude; speeding up means increased frequency.
Therefore, for the half cycle inwhich there is a hit, a shorter amplitude
and hence instantaneous higher frequency exists.
I understand perfectly and explained it for you in excruciating detail.
The change in phase of the Shortt clock slave pendulum is due to the FIRST
ORDER change in the effective gravitational constant in the pendulum
equation by engaging the leaf spring. While the reduced amplitude of the
swing *will* cause a SECOND ORDER effect in the motion of the pendulum, it
will be MUCH SMALLER than the FIRST ORDER effect.
What part of this do you not understand or not agree with?
It's not that I do not understand nor disagree with you, it's that
you're off on a complete tangent to what I was suggesting, and
do not realise it.
Sorry, I was talking about how the Shortt clock adjusts the timing of the
slave pendulum. What are you talking about?
I ... explained it for you in excruciating detail.
No, you simply state that the circular error exists for pendulum clocks and
that the swing of the Shortt clock slave pendulum is shortened a small
amount. You imply the shorter swing of the pendulum invokes the circular
error factor to change the speed of the pendulum changing the phase.

None of that is wrong. But the circular arc error a very small effect. As
I have clearly explained to you the leaf spring also causes the first order
effect of changing the constant in the pendulum equation. This is a *much*
larger effect than the small circular error effect.

You say you understand what I am saying, but it directly shows what you are
describing is at best, a second order effect. If you don't disagree with
that how can it be tangential to what you are saying? Or is that a play on
words with the circular error???
--
Rick C
Brian Reay
2017-08-06 18:09:45 UTC
Permalink
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Post by Gareth's Downstairs Computer
Post by rickman
Post by Gareth's Downstairs Computer
Post by rickman
You seem to be completely misunderstanding the operation of the Shortt
clock. The slave pendulum has no need for correction of circular error.
I'm sorry, but you totally misunderstood what I was saying, which was
that because all pendulums exhibit circular error, when the hit occurs
in the hit and miss synchroniser and foreshortens the swing, then, for
that half-cycle, and only that half cycle, the frequency is
changed, as it must be.
Just as in the electronic PLL, instantaneous changes of phase have
instantaneous changes of frequency, no matter how short lived,
associated with them.
What you say about frequency vs. phase is true and how the Shortt
clock adjusts phase, but it has nothing to do with circular error of
the pendulum. The correction of the phase is from the added spring
resistance shortening the time as well as the travel of the pendulum.
The fact that the swing is shorter and the second order circular error
will create a tiny error in the timing is pretty much irrelevant. The
real change is from the added spring constant changing the first order
effect in the pendulum equation. The coefficient of the gravitational
constant is effectively changed by the spring.
Is that more clear?
You continue to misunderstand. Any pendulum swinging with circular error
speeds up for shorter amplitude; speeding up means increased frequency.
Therefore, for the half cycle inwhich there is a hit, a shorter
amplitude and hence instantaneous higher frequency exists.
Nothing in any of rick's posts he does understand the above, or anything
else. Plus, what you have posted is exactly what I explained to you
earlier.

It is clear you are on the edge of resorting to your normal abuse.
Peter Fairbrother
2017-08-05 15:01:26 UTC
Permalink
Raw Message
Post by Chris
Post by Jeff
Rubbish, the function of a phase locked loop is to keep the phase of the
2 signals the same, within the constraints of the loop filter.
The clock *never* achieves this, it is open loop and applies a 'kick' to
one pendulum the amplitude of which is NOT related to the difference in
phase of the 2 pendulums.
The amplitude is not, but the frequency is - why do you think the
amplitude should be related to the difference in phase?
Post by Chris
Post by Jeff
A fixed kick is given without any knowledge that it will be of the
correct amplitude to achieve an in phase or near in phase condition.
There is NO feedback of an error signal that relates to the phase
difference between the 2 pendulums.
Ah, yes there is, see below.
Post by Chris
Post by Jeff
The only time phase comes into the picture is the timing of when the
'kick' is given, so as not to disrupt the normal swing of the pendulum,
and whether or not to give a kick at all.
Are you referring to the kick given to the master pendulum? That is not
part of the PLL system. The kicks given to the master pendulum are
specifically designed not to affect the phase of the master pendulum at all.

If not, if you are referring to the kick given to the slave pendulum
(these are quite different kicks) that is not how the clock works.

The slave pendulum is kicked from time to time, ad kicked a little more
often when the phases get too far apart - the difference in phases is
the error signal mentioned above - and these kicks do affect the phase
of the slave pendulum.
Post by Chris
Exactly. The control is single path, master to slave, with no feedback
to the reference, making it an open loop design. The master has no
knowledge of the state of the slave at any time.
That is exactly what a PLL is - and it is almost (though not quite) what
this clock does. It is certainly what the slave does.
Post by Chris
In a pll, there is continuous
Not necessarily continuous - a bang-bang action is allowable, and does
not prevent a system from being a PLL.
Post by Chris
feedback from the vco to the phase
detector, closing the loop and keeping the phase offset constant,
A PLL does not necessarily keep the phase offset constant, just within
the interval =/- 2pi.
Post by Chris
The phase is continuously updated every cycle,
Not necessarily continuously updated, or updated every cycle - as long
as the offset is continuously within the range -2pi to 2pi, the phases
are locked.
Post by Chris
whereas the Shortt
clock can have significant accumulated error in the time between
corrections...
Yes - but that doesn't mean it is not a PLL, as long as the error is
less than +/- 2pi.



A phase-locked loop is a system which produces a (slave) vibration the
integral of whose phase in comparison to the phase of another (master)
vibration is continuously between -2pi and 2pi over long periods.

A last requirement is that the phase-locked loop system should have no
effect whatsoever on the master vibration. That's it.

If it does that, the phases are locked - they may not be tightly locked,
but the vibrations do not skip or add beats.

More advanced PLLs might keep the difference between phases much
smaller, as in this clock - but that is not a requirement of a PLL.
There is no such thing as absolutely tightly locked, there is only
unlocked or locked.

Neither is continuous updating necessary, though the integral should be
continuously in that interval.

In this clock the hit-and-miss synchroniser action undoubtedly does act
as a PLL.

However it might be argued that the slave does subsequently have some
(very small) input to the master, when it operates the gravity drive
(whuzzat? I am not a clockmaker).

That certainly has an effect on the amplitude of the master; although as
the idea an intention and practical effect is that it has no effect
whatsoever on the phase of the master, thus the slave clock action
overall most definitely should be considered a PLL.

-- Peter Fairbrother

ps; the +/- 2pi bit is not really a requirement either, as long as the
system can keep count of the missing/extra beats - but as most systems
don't do that we shall just gracefully ignore that for now ..
rickman
2017-08-05 15:19:06 UTC
Permalink
Raw Message
Post by Chris
Post by Jeff
Rubbish, the function of a phase locked loop is to keep the phase of the
2 signals the same, within the constraints of the loop filter.
The clock *never* achieves this, it is open loop and applies a 'kick' to
one pendulum the amplitude of which is NOT related to the difference in
phase of the 2 pendulums.
The amplitude is not, but the frequency is - why do you think the amplitude
should be related to the difference in phase?
Post by Chris
Post by Jeff
A fixed kick is given without any knowledge that it will be of the
correct amplitude to achieve an in phase or near in phase condition.
There is NO feedback of an error signal that relates to the phase
difference between the 2 pendulums.
Ah, yes there is, see below.
Post by Chris
Post by Jeff
The only time phase comes into the picture is the timing of when the
'kick' is given, so as not to disrupt the normal swing of the pendulum,
and whether or not to give a kick at all.
Are you referring to the kick given to the master pendulum? That is not part
of the PLL system. The kicks given to the master pendulum are specifically
designed not to affect the phase of the master pendulum at all.
If not, if you are referring to the kick given to the slave pendulum (these
are quite different kicks) that is not how the clock works.
The slave pendulum is kicked from time to time, ad kicked a little more
often when the phases get too far apart - the difference in phases is the
error signal mentioned above - and these kicks do affect the phase of the
slave pendulum.
What they fail to see is that the amplitude of the kick *is* adjusted. It's
just the adjustment is binary, on or off. But that is still *adjustment*
and is in response to the measured phase.
Post by Chris
Exactly. The control is single path, master to slave, with no feedback
to the reference, making it an open loop design. The master has no
knowledge of the state of the slave at any time.
That is exactly what a PLL is - and it is almost (though not quite) what
this clock does. It is certainly what the slave does.
Post by Chris
In a pll, there is continuous
Not necessarily continuous - a bang-bang action is allowable, and does not
prevent a system from being a PLL.
Post by Chris
feedback from the vco to the phase
detector, closing the loop and keeping the phase offset constant,
A PLL does not necessarily keep the phase offset constant, just within the
interval =/- 2pi.
Not only that, but if you examine the equations for a PLL you will find it
is *impossible* to maintain a constant phase offset with any variations in
the reference or noise in the system.
Post by Chris
The phase is continuously updated every cycle,
Not necessarily continuously updated, or updated every cycle - as long as
the offset is continuously within the range -2pi to 2pi, the phases are locked.
Post by Chris
whereas the Shortt
clock can have significant accumulated error in the time between
corrections...
Yes - but that doesn't mean it is not a PLL, as long as the error is less
than +/- 2pi.
A phase-locked loop is a system which produces a (slave) vibration the
integral of whose phase in comparison to the phase of another (master)
vibration is continuously between -2pi and 2pi over long periods.
A last requirement is that the phase-locked loop system should have no
effect whatsoever on the master vibration. That's it.
If it does that, the phases are locked - they may not be tightly locked, but
the vibrations do not skip or add beats.
More advanced PLLs might keep the difference between phases much smaller, as
in this clock - but that is not a requirement of a PLL. There is no such
thing as absolutely tightly locked, there is only unlocked or locked.
Neither is continuous updating necessary, though the integral should be
continuously in that interval.
In this clock the hit-and-miss synchroniser action undoubtedly does act as a
PLL.
However it might be argued that the slave does subsequently have some (very
small) input to the master, when it operates the gravity drive (whuzzat? I
am not a clockmaker).
That certainly has an effect on the amplitude of the master; although as the
idea an intention and practical effect is that it has no effect whatsoever
on the phase of the master, thus the slave clock action overall most
definitely should be considered a PLL.
-- Peter Fairbrother
ps; the +/- 2pi bit is not really a requirement either, as long as the
system can keep count of the missing/extra beats - but as most systems don't
do that we shall just gracefully ignore that for now ..
In a typical PLL isn't the requirement to be within +/- pi rather than 2 pi?
If you exceed a range of +/- pi from the intended alignment the feedback
will start to push the controlled oscillator further out of alignment
potentially aligning with another cycle of the master.
--
Rick C
Peter Fairbrother
2017-08-05 16:05:38 UTC
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[..
Post by rickman
The slave pendulum is kicked from time to time, and kicked a little more
often when the phases get too far apart - the difference in phases is the
error signal mentioned above - and these kicks do affect the phase of the
slave pendulum.
What they fail to see is that the amplitude of the kick *is* adjusted.
It's just the adjustment is binary, on or off. But that is still
*adjustment* and is in response to the measured phase.
Yup.

Compare with pwm (pulse width modulation) or ppm (pulse position
modulation) - I forget what the actual modulation in the clock is
called, but it is just another modulation, despite being binary and
fixed in amplitude.
Post by rickman
A PLL does not necessarily keep the phase offset constant, just within
the interval +/- 2pi.
Not only that, but if you examine the equations for a PLL you will find
it is *impossible* to maintain a constant phase offset with any
variations in the reference or noise in the system.
Indeed.. in some ultimate sense, perhaps that is the final purpose of a
PLL.
Post by rickman
ps; the +/- 2pi bit is not really a requirement either, as long as the
system can keep count of the missing/extra beats - but as most systems don't
do that we shall just gracefully ignore that for now ..
In a typical PLL isn't the requirement to be within +/- pi rather than 2
pi? If you exceed a range of +/- pi from the intended alignment the
feedback will start to push the controlled oscillator further out of
alignment potentially aligning with another cycle of the master.
Yes, in a typical PLL - however I was considering a more theoretical one
where eg the phase offset was known to be positive or negative.



On reflection, is a system where the phases are several full cycles
out-of-phase, but where the system over time adjusts the slave to (close
to) the actual phase of the master, still a PLL?

On further reflection, I think it must be - so perhaps a better
definition might be that the integral of the phase difference remains
close to zero over long periods time (while leaving how close and how
long as an exercise for the reader) :) .

-- Peter F
rickman
2017-08-05 14:46:59 UTC
Permalink
Raw Message
Post by rickman
What we are seeing is that even after the 30 second 'kick' the 2 pendulums
are NOT in phase.
They may well be 'a bit closer' in phase, but the kick just moves the
difference a fixed small amount in one direction, which may be sufficient to
bring the phases closer, or it may be too much and go through the in phase
point. With the design there is no time where the 2 pendulums are *held* in
phase.
The design in fact relies on the fact that the phase of the 2 pendulums is
constantly changing.
As is true for any PLL.
Rubbish, the function of a phase locked loop is to keep the phase of the 2
signals the same, within the constraints of the loop filter.
The clock *never* achieves this, it is open loop and applies a 'kick' to one
pendulum the amplitude of which is NOT related to the difference in phase of
the 2 pendulums.
A fixed kick is given without any knowledge that it will be of the correct
amplitude to achieve an in phase or near in phase condition. There is NO
feedback of an error signal that relates to the phase difference between the
2 pendulums.
The only time phase comes into the picture is the timing of when the 'kick'
is given, so as not to disrupt the normal swing of the pendulum, and whether
or not to give a kick at all.
It is and ingenious system, but not a phase locked loop.
I guess it could be closer to a PLL if the kick had its amplitude varied by
the phase difference between the 2 pendulums, but you still have the problem
that if you were in the state where no kick was required there is no way of
slowing the second pendulum without waiting for it to drift back, so it is
still open loop.
You are making pointless distinctions. A phase locked loop is not defined
by its mechanics but by the nature of its control. The Shortt clock
maintains the relative *phase* of the two clocks by brief adjustments to the
frequency via a spring. This is controlled by measuring the relative
*phase* of the two clocks.

It's that simple. You are just making things more complicated by talking
about the details of how the adjustment works and the time function of the
frequency. NO PLL can keep the two clocks perfectly in sync.

Calling it open loop is just absurd. The loop is closed because it
*measures* the phase of the clocks and adjusts the phase according to the
measurement. It may be binary, but the adjustment is controlled by the
measurement.
--
Rick C
Jeff
2017-08-06 10:38:27 UTC
Permalink
Raw Message
Post by rickman
You are making pointless distinctions. A phase locked loop is not
defined by its mechanics but by the nature of its control. The Shortt
clock maintains the relative *phase* of the two clocks by brief
adjustments to the frequency via a spring. This is controlled by
measuring the relative *phase* of the two clocks.
Wrong! It does NOT measure the relative phase, it makes NO measurement
of the phase difference. All it does is detect if there is a phase lag
of any degree. It could be a fraction of a degree or 180 degrees, the
same correction is then applied regardless.
Post by rickman
It's that simple. You are just making things more complicated by
talking about the details of how the adjustment works and the time
function of the frequency. NO PLL can keep the two clocks perfectly in
sync.
Calling it open loop is just absurd. The loop is closed because it
*measures* the phase of the clocks and adjusts the phase according to
the measurement. It may be binary, but the adjustment is controlled by
the measurement.
Wrong again it is open loop, there is no measurement, just the same
adjustment regardless of the phase difference.

Jeff
Chris
2017-08-06 11:24:10 UTC
Permalink
Raw Message
Post by Jeff
You are making pointless distinctions. A phase locked loop is not
defined by its mechanics but by the nature of its control. The Shortt
clock maintains the relative *phase* of the two clocks by brief
adjustments to the frequency via a spring. This is controlled by
measuring the relative *phase* of the two clocks.
Wrong! It does NOT measure the relative phase, it makes NO measurement
of the phase difference. All it does is detect if there is a phase lag
of any degree. It could be a fraction of a degree or 180 degrees, the
same correction is then applied regardless.
It's that simple. You are just making things more complicated by
talking about the details of how the adjustment works and the time
function of the frequency. NO PLL can keep the two clocks perfectly in
sync.
Calling it open loop is just absurd. The loop is closed because it
*measures* the phase of the clocks and adjusts the phase according to
the measurement. It may be binary, but the adjustment is controlled by
the measurement.
Wrong again it is open loop, there is no measurement, just the same
adjustment regardless of the phase difference.
Jeff
Might be easier to define a set entitled "Locked Oscillators, of which
the phase locked loop, injection locked and hit and miss synchronised
are all members.

Are there other candidates ?...

Chris
Gareth's Downstairs Computer
2017-08-06 12:52:23 UTC
Permalink
Raw Message
Post by Chris
Post by Jeff
You are making pointless distinctions. A phase locked loop is not
defined by its mechanics but by the nature of its control. The Shortt
clock maintains the relative *phase* of the two clocks by brief
adjustments to the frequency via a spring. This is controlled by
measuring the relative *phase* of the two clocks.
Wrong! It does NOT measure the relative phase, it makes NO measurement
of the phase difference. All it does is detect if there is a phase lag
of any degree. It could be a fraction of a degree or 180 degrees, the
same correction is then applied regardless.
It's that simple. You are just making things more complicated by
talking about the details of how the adjustment works and the time
function of the frequency. NO PLL can keep the two clocks perfectly in
sync.
Calling it open loop is just absurd. The loop is closed because it
*measures* the phase of the clocks and adjusts the phase according to
the measurement. It may be binary, but the adjustment is controlled by
the measurement.
Wrong again it is open loop, there is no measurement, just the same
adjustment regardless of the phase difference.
Jeff
Might be easier to define a set entitled "Locked Oscillators, of which
the phase locked loop, injection locked and hit and miss synchronised
are all members.
Are there other candidates ?...
From pre-war, the Goyder Lock?

Which raises an interesting point; before the 3-tier
coffer-filling fiasco was the spawn of the RSCB, the candidature
for the RAE tended to know all about the history of amateur radio
before getting their licence, but now they seem to know
sweet FA even after getting their licences, such as the
difference between sideband and sidetone.
mm0fmf
2017-08-06 13:00:01 UTC
Permalink
Raw Message
Post by Gareth's Downstairs Computer
Post by Chris
Post by Jeff
You are making pointless distinctions. A phase locked loop is not
defined by its mechanics but by the nature of its control. The Shortt
clock maintains the relative *phase* of the two clocks by brief
adjustments to the frequency via a spring. This is controlled by
measuring the relative *phase* of the two clocks.
Wrong! It does NOT measure the relative phase, it makes NO measurement
of the phase difference. All it does is detect if there is a phase lag
of any degree. It could be a fraction of a degree or 180 degrees, the
same correction is then applied regardless.
It's that simple. You are just making things more complicated by
talking about the details of how the adjustment works and the time
function of the frequency. NO PLL can keep the two clocks perfectly in
sync.
Calling it open loop is just absurd. The loop is closed because it
*measures* the phase of the clocks and adjusts the phase according to
the measurement. It may be binary, but the adjustment is controlled by
the measurement.
Wrong again it is open loop, there is no measurement, just the same
adjustment regardless of the phase difference.
Jeff
Might be easier to define a set entitled "Locked Oscillators, of which
the phase locked loop, injection locked and hit and miss synchronised
are all members.
Are there other candidates ?...
From pre-war, the Goyder Lock?
Which raises an interesting point; before the 3-tier
coffer-filling fiasco was the spawn of the RSCB, the candidature
for the RAE tended to know all about the history of amateur radio
before getting their licence, but now they seem to know
sweet FA even after getting their licences, such as the
difference between sideband and sidetone.
House!
Chris
2017-08-06 14:27:36 UTC
Permalink
Raw Message
Post by Gareth's Downstairs Computer
Post by Chris
Post by Jeff
You are making pointless distinctions. A phase locked loop is not
defined by its mechanics but by the nature of its control. The Shortt
clock maintains the relative *phase* of the two clocks by brief
adjustments to the frequency via a spring. This is controlled by
measuring the relative *phase* of the two clocks.
Wrong! It does NOT measure the relative phase, it makes NO measurement
of the phase difference. All it does is detect if there is a phase lag
of any degree. It could be a fraction of a degree or 180 degrees, the
same correction is then applied regardless.
It's that simple. You are just making things more complicated by
talking about the details of how the adjustment works and the time
function of the frequency. NO PLL can keep the two clocks perfectly in
sync.
Calling it open loop is just absurd. The loop is closed because it
*measures* the phase of the clocks and adjusts the phase according to
the measurement. It may be binary, but the adjustment is controlled by
the measurement.
Wrong again it is open loop, there is no measurement, just the same
adjustment regardless of the phase difference.
Jeff
Might be easier to define a set entitled "Locked Oscillators, of which
the phase locked loop, injection locked and hit and miss synchronised
are all members.
Are there other candidates ?...
From pre-war, the Goyder Lock?
Which raises an interesting point; before the 3-tier
coffer-filling fiasco was the spawn of the RSCB, the candidature
for the RAE tended to know all about the history of amateur radio
before getting their licence, but now they seem to know
sweet FA even after getting their licences, such as the
difference between sideband and sidetone.
Hadn't heard of that, so looked it up and found:

http://www.dxmaps.com/discuss/oven.html

Which was an interesting read, but not enlightening.

Some of the early scope timebases, puckle, for example sounded
interesting, but they were effectively injection lock, of course.
I guess a triggered timebase is a variation of the hit and miss model.

Couldn't grok the relevance of the following paragraph above :-)...

Chris
Gareth's Downstairs Computer
2017-08-06 17:34:37 UTC
Permalink
Raw Message
Post by Chris
Post by Gareth's Downstairs Computer
Post by Chris
Post by Jeff
You are making pointless distinctions. A phase locked loop is not
defined by its mechanics but by the nature of its control. The Shortt
clock maintains the relative *phase* of the two clocks by brief
adjustments to the frequency via a spring. This is controlled by
measuring the relative *phase* of the two clocks.
Wrong! It does NOT measure the relative phase, it makes NO measurement
of the phase difference. All it does is detect if there is a phase lag
of any degree. It could be a fraction of a degree or 180 degrees, the
same correction is then applied regardless.
It's that simple. You are just making things more complicated by
talking about the details of how the adjustment works and the time
function of the frequency. NO PLL can keep the two clocks perfectly in
sync.
Calling it open loop is just absurd. The loop is closed because it
*measures* the phase of the clocks and adjusts the phase according to
the measurement. It may be binary, but the adjustment is controlled by
the measurement.
Wrong again it is open loop, there is no measurement, just the same
adjustment regardless of the phase difference.
Jeff
Might be easier to define a set entitled "Locked Oscillators, of which
the phase locked loop, injection locked and hit and miss synchronised
are all members.
Are there other candidates ?...
From pre-war, the Goyder Lock?
Which raises an interesting point; before the 3-tier
coffer-filling fiasco was the spawn of the RSCB, the candidature
for the RAE tended to know all about the history of amateur radio
before getting their licence, but now they seem to know
sweet FA even after getting their licences, such as the
difference between sideband and sidetone.
http://www.dxmaps.com/discuss/oven.html
Which was an interesting read, but not enlightening.
Some of the early scope timebases, puckle, for example sounded
interesting, but they were effectively injection lock, of course.
I guess a triggered timebase is a variation of the hit and miss model.
Couldn't grok the relevance of the following paragraph above :-)...
It relates to the abysmal lack of technical acumen amongst those
who are today's would-br radio amateurs, most of whom are
really CBers-masquerading-as-radio-hams, identifiable by their
M3 and M6 callsigns past and present.
Chris
2017-08-06 18:58:54 UTC
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Post by Gareth's Downstairs Computer
It relates to the abysmal lack of technical acumen amongst those
who are today's would-br radio amateurs, most of whom are
really CBers-masquerading-as-radio-hams, identifiable by their
M3 and M6 callsigns past and present.
Perhaps you are right, but does that matter ?. Might not all have
the tech ability of the past, but just as keen on operating and
the social aspects of the hobby. We can't all be tech experts, but
there are still plenty of deep tech areas for those interested.

Seems a bit of an elitist attitude really, speaking as one who
built his first one valve set at 11 and always more interested
in the tech side than operating...

Chris
Gareth's Downstairs Computer
2017-08-06 19:18:51 UTC
Permalink
Raw Message
Post by Chris
Post by Gareth's Downstairs Computer
It relates to the abysmal lack of technical acumen amongst those
who are today's would-br radio amateurs, most of whom are
really CBers-masquerading-as-radio-hams, identifiable by their
M3 and M6 callsigns past and present.
Perhaps you are right, but does that matter ?. Might not all have
the tech ability of the past, but just as keen on operating and
the social aspects of the hobby. We can't all be tech experts, but
there are still plenty of deep tech areas for those interested.
Seems a bit of an elitist attitude really, speaking as one who
built his first one valve set at 11 and always more interested
in the tech side than operating...
Elitism, yes, and something to be jealously guarded.

AIUI, there are already countries where only commercially
available rigs may be used, and by flooding this country
with technical numbskulls risks the powers-that-would-be
perceiving we all as operators only.

Amateur radio is primarily a technical pursuit with operation
being a trivially simple follow-on; so trivially simple, in fact,
that it is a nonsense to examine based upon operating. The 5-year-old
with her smartphone does not have to pass an exam on her operating
capability!

As to your last comment, Yes, more technician than operative,
I still maintain a logbook, with all test
and CQ calls logged, and yet after 47 years I'm only just half way
through my 2nd log book.
mm0fmf
2017-08-06 19:26:57 UTC
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Post by Gareth's Downstairs Computer
Amateur radio is primarily a technical pursuit with operation
being a trivially simple follow-on; so trivially simple, in fact,
that it is a nonsense to examine based upon operating.
If operating is so trivially simple why couldn't you tune the PA in the
radio you bought? Even CBers can do that.
Roger Hayter
2017-08-06 19:45:21 UTC
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Post by mm0fmf
Post by Gareth's Downstairs Computer
Amateur radio is primarily a technical pursuit with operation
being a trivially simple follow-on; so trivially simple, in fact,
that it is a nonsense to examine based upon operating.
If operating is so trivially simple why couldn't you tune the PA in the
radio you bought? Even CBers can do that.
Do you need to trade silly (and, yes, typically junior school stuff)
abuse rehearsed from interminable local arguments all over the Internet?
Why not keep this childish repetitive stuff for ukra where it "belongs"?
You *are* an adult, aren't you? Gareth's silly comments are quite
obviously silly comments without you clutttering the place up arguing
with him about it. If you think his comments about operating being too
easy and of no interest are inaccurate, why not say so, at least it will
soon be obvious he is in a minority of one? I for instance have very
little interest in operating but agree that it is an essential and
worthy part of the hobby (and not so easy as Gareth thinks) so why not
stick to the actual issue when discussing it internationally and outside
of the AR groups?
--
Roger Hayter
Bernie
2017-08-06 20:15:46 UTC
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Raw Message
On Sun, 6 Aug 2017 20:45:21 +0100
Post by Roger Hayter
Post by mm0fmf
Post by Gareth's Downstairs Computer
Amateur radio is primarily a technical pursuit with operation
being a trivially simple follow-on; so trivially simple, in fact,
that it is a nonsense to examine based upon operating.
If operating is so trivially simple why couldn't you tune the PA in
the radio you bought? Even CBers can do that.
Do you need to trade silly (and, yes, typically junior school stuff)
abuse rehearsed from interminable local arguments all over the
Internet? Why not keep this childish repetitive stuff for ukra where
it "belongs"? You *are* an adult, aren't you? Gareth's silly
comments are quite obviously silly comments without you clutttering
the place up arguing with him about it. If you think his comments
about operating being too easy and of no interest are inaccurate, why
not say so, at least it will soon be obvious he is in a minority of
one? I for instance have very little interest in operating but agree
that it is an essential and worthy part of the hobby (and not so easy
as Gareth thinks) so why not stick to the actual issue when
discussing it internationally and outside of the AR groups?
Isn't that post just your own version of deriding others' comments and
"cluttering the place up" with pointless opinion posts, though, Roger?

Or are your posts somehow intrinsically superior?

Personally, I'd tell you to go fuck yourself.
Brian Reay
2017-08-06 20:26:48 UTC
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Post by Bernie
On Sun, 6 Aug 2017 20:45:21 +0100
Post by Roger Hayter
Post by mm0fmf
Post by Gareth's Downstairs Computer
Amateur radio is primarily a technical pursuit with operation
being a trivially simple follow-on; so trivially simple, in fact,
that it is a nonsense to examine based upon operating.
If operating is so trivially simple why couldn't you tune the PA in
the radio you bought? Even CBers can do that.
Do you need to trade silly (and, yes, typically junior school stuff)
abuse rehearsed from interminable local arguments all over the
Internet? Why not keep this childish repetitive stuff for ukra where
it "belongs"? You *are* an adult, aren't you? Gareth's silly
comments are quite obviously silly comments without you clutttering
the place up arguing with him about it. If you think his comments
about operating being too easy and of no interest are inaccurate, why
not say so, at least it will soon be obvious he is in a minority of
one? I for instance have very little interest in operating but agree
that it is an essential and worthy part of the hobby (and not so easy
as Gareth thinks) so why not stick to the actual issue when
discussing it internationally and outside of the AR groups?
Isn't that post just your own version of deriding others' comments and
"cluttering the place up" with pointless opinion posts, though, Roger?
Or are your posts somehow intrinsically superior?
Not superior, just as ever with Roger, 'selective'- he never chastises
his chum for his behaviour. Hardly surprising as they clearly have so
much in common, as his behaviour in ukram shows.
mm0fmf
2017-08-06 20:27:16 UTC
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Raw Message
Post by Bernie
On Sun, 6 Aug 2017 20:45:21 +0100
Post by Roger Hayter
Post by mm0fmf
Post by Gareth's Downstairs Computer
Amateur radio is primarily a technical pursuit with operation
being a trivially simple follow-on; so trivially simple, in fact,
that it is a nonsense to examine based upon operating.
If operating is so trivially simple why couldn't you tune the PA in
the radio you bought? Even CBers can do that.
Do you need to trade silly (and, yes, typically junior school stuff)
abuse rehearsed from interminable local arguments all over the
Internet? Why not keep this childish repetitive stuff for ukra where
it "belongs"? You *are* an adult, aren't you? Gareth's silly
comments are quite obviously silly comments without you clutttering
the place up arguing with him about it. If you think his comments
about operating being too easy and of no interest are inaccurate, why
not say so, at least it will soon be obvious he is in a minority of
one? I for instance have very little interest in operating but agree
that it is an essential and worthy part of the hobby (and not so easy
as Gareth thinks) so why not stick to the actual issue when
discussing it internationally and outside of the AR groups?
Isn't that post just your own version of deriding others' comments and
"cluttering the place up" with pointless opinion posts, though, Roger?
Or are your posts somehow intrinsically superior?
Personally, I'd tell you to go fuck yourself.
I told the sanctimonious shite to go fuck himself a long time ago.
Brian Reay
2017-08-06 19:24:01 UTC
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Post by Chris
Post by Gareth's Downstairs Computer
It relates to the abysmal lack of technical acumen amongst those
who are today's would-br radio amateurs, most of whom are
really CBers-masquerading-as-radio-hams, identifiable by their
M3 and M6 callsigns past and present.
Perhaps you are right, but does that matter ?. Might not all have
the tech ability of the past, but just as keen on operating and
the social aspects of the hobby. We can't all be tech experts, but
there are still plenty of deep tech areas for those interested.
Seems a bit of an elitist attitude really, speaking as one who
built his first one valve set at 11 and always more interested
in the tech side than operating...
That puts you ahead of Gareth, he still hasn't finished building his by
his own admission it has been several decades.
rickman
2017-08-06 16:23:33 UTC
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Post by rickman
You are making pointless distinctions. A phase locked loop is not defined
by its mechanics but by the nature of its control. The Shortt clock
maintains the relative *phase* of the two clocks by brief adjustments to
the frequency via a spring. This is controlled by measuring the relative
*phase* of the two clocks.
Wrong! It does NOT measure the relative phase, it makes NO measurement of
the phase difference. All it does is detect if there is a phase lag of any
degree. It could be a fraction of a degree or 180 degrees, the same
correction is then applied regardless.
...and that is a measurement. It determines if the relative phase is plus
or minus, a binary measurement. This is exactly the same as the measurement
taken by a 1 bit ADC. Even though it is one bit it is still a measurement.
Post by rickman
It's that simple. You are just making things more complicated by talking
about the details of how the adjustment works and the time function of the
frequency. NO PLL can keep the two clocks perfectly in sync.
Calling it open loop is just absurd. The loop is closed because it
*measures* the phase of the clocks and adjusts the phase according to the
measurement. It may be binary, but the adjustment is controlled by the
measurement.
Wrong again it is open loop, there is no measurement, just the same
adjustment regardless of the phase difference.
Totally wrong. The phase adjustment varies from a constant about to ZERO!
Again it is a binary adjustment.

If there was a three level range of measurement and adjustment +, 0, -,
would that be enough to constitute a measurement and adjustment so it
becomes a PLL? If not, how many bits are required? If any number of bits
can't do it are digital PLLs not PLLs?
--
Rick C
j***@specsol.spam.sux.com
2017-08-04 16:07:12 UTC
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Post by Jeff
Post by rickman
I don't know what you guys are seeing. The two pendulums of the Shortt
clock are in lock step. The fact that they are only compared every 30
seconds does not change the nature of the design.
What we are seeing is that even after the 30 second 'kick' the 2
pendulums are NOT in phase.
They may well be 'a bit closer' in phase, but the kick just moves the
difference a fixed small amount in one direction, which may be
sufficient to bring the phases closer, or it may be too much and go
through the in phase point. With the design there is no time where the 2
pendulums are *held* in phase.
The design in fact relies on the fact that the phase of the 2 pendulums
is constantly changing.
Jeff
https://en.wikipedia.org/wiki/Shortt%E2%80%93Synchronome_clock#Hit_and_miss_synchronizer

"This feedback loop functioned as an electromechanical version of a
phase-locked loop..."
--
Jim Pennino
Jeff
2017-08-05 09:46:25 UTC
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Post by j***@specsol.spam.sux.com
https://en.wikipedia.org/wiki/Shortt%E2%80%93Synchronome_clock#Hit_and_miss_synchronizer
"This feedback loop functioned as an electromechanical version of a
phase-locked loop..."
..and of course everything on Wikki is correct!!!

Jeff
j***@specsol.spam.sux.com
2017-08-05 16:03:57 UTC
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Post by Jeff
Post by j***@specsol.spam.sux.com
https://en.wikipedia.org/wiki/Shortt%E2%80%93Synchronome_clock#Hit_and_miss_synchronizer
"This feedback loop functioned as an electromechanical version of a
phase-locked loop..."
..and of course everything on Wikki is correct!!!
Jeff
The usual cry of those who have not bothered to do any research on a
subject and are shown a Wiki article that contradicts their position
is that Wiki can be edited by anybody.

Wiki is more correct than most of the babble on USENET and the Wiki article
has 18 external references to back it up.

Where is your annotated list of references?

Here's another site that says the same thing:

http://www.meccanotec.com/shortt.html

"The slave is kept in synchrony with the master in a phase locked loop."
--
Jim Pennino
Jerry Stuckle
2017-08-04 02:25:09 UTC
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Post by Chris
Not sure if you are referring to the Shortt clock or the PLL. But the
statement applies equally to both. There is no magical stability in the
PLL. It is a control loop and as such the thing being controlled will
*never* remain in phase or at the same frequency as the reference.
I think the difference is that while a pll always has a phase offset
the reference and vco are in phase lockstep once the loop has aquired
lock. It's a closed loop system whereas the Shortt clock is an open
loop system, only getting a kick back into sync from time to time.
Like a hit and miss governor ?...
Chris
In this case I have to (surprise!) agree with Rickman. A phase locked
loop is never in lockstep with the reference - there is always a bit of
drift in the oscillator.

It's no different than driving down a highway. You can aim your car
straight down the road - but you need to continually make small
adjustments to account for things like the road and the wind.

The Shortt clock is not that much different, except that it purposely
runs at a slightly lower frequency than the reference, and the frequency
at which the comparison occurs is much lower.

But the result is the same - a signal that is accurate due to
compensation based on the instantaneous phase at specific times.
--
==================
Remove the "x" from my email address
Jerry Stuckle
***@attglobal.net
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