"Geoff" <***@nospam.demon.co.uk> wrote in message
> "Brian Reay" <***@bigfoot.com> wrote in news:***@uni-
> > "Chris Kirby" <***@yahoo.com> wrote in message
> > news:***@4ax.com...
> >> Geoff wrote:
> >> >In what way Walt? 250W on 2m will go a fair way, considerably further
> >> >than (say) 20m. As you well know, EME is possible with 250W on 2m.
> >> It's erp that counts and I doubt that eme is possible with 250w erp.
> > 250W erp is 24dBW, near enough.
> > The free space path loss for EME at 144MHz is about 250dB, as I recall.
> > (That doesn't allow for losses in the reflection process)
> > So, the return signal is, at most, -226dBW, or -196dBm
> > Even without going as far as allowing for the SNR benefits of a narrow
> > bandwidth, rx antenna gain, etc that looks like needing an 'impressive'
> > receiver ;-)
> As a matter of interest, EME is workable on 2m at the 200W level using a
> single Yagi. See http://www.gm4jjj.co.uk/K6PF/k6pf.pdf for an example. I
> was, of course, talking about a power amplifier output (the Dressler,
> we came in) of ~+24dBW, not the ERP, which would more probably be around
> the +38dBW mark given a single long Yagi.
That is still leaving a lot to the recieving system- what will a good VHF rx
manage these days on SSB, say -120dBm for 10dB S/N ?
Reducing the bandwidth to, say, 300Hz gives us, say 10dB. Say another (net)
10dB for the rx antenna and feeder?
So, the original -196dBm, the +12dB from your revised number, +10dB for
the BW reduction, +10dB for the antenna and feeder.
Looks like -164dBm
OK, we don't need 10dB S/N at the rx but we've also assumed the moon is a
I've scanned the pdf file but didn't notice a detailed link budget. I expect
there is on on the web somewhere.
> Also, my "old" single 4CX350A linear was capable of nearer +27dBW on
> My point, to the original post in the sub-context, GM8EOG, was that his
> assertation that 200W on 2m would only go a "medium distance" was rather
> incorrect. If ~500,000 miles ia medium distance, what is "real DX", Mars
> maybe (yes I know the Mars spacecraft have been heard by amateurs on
> 8.4GHz., but that is hardly 2m!).
Well, if we are being pedantic, the RF energy goes the same distance
regardless of frequency in free space, it just gets harder to make use of it
> Of course, Walt jumped in with both feet and little thought, as usual, but
> one rather expects that.
Yes, one does. If Walt passes it by I expect we can be sure the Chippenham
idiot won't ;-)
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