G0MGX via rec.radio.amateur.moderated Admin
2017-06-11 15:17:07 UTC
Its brick time!
Posted: 11 Jun 2017 07:53 AM PDT
To compliment the DATV transmitter I made here, I've been building a PA
rated at 60W RF out - it will be used at way less than this, but for any
kind of TV transmission we need loads of overhead in the PA to avoid
nastyness in the output.
The PA is this design here, the PCB from G4DDK.
The module itself is a RA60H1317M1A and I got mine from Anglia Live.
The heatsink feels like a great find, I saw it listed on eBay by JPG
Electronics in Chesterfield; as it's just up the road I paid a visit - what
a find! Loads of goodies!
Anyhow, here the PA under test:
The TX RF from the Portsdown will come in through the LPF we tested last
time; then through the PA and out through the SMA relay. The RX Signal will
pass through the BPF also from last time, and to the Receiver we made here.
The relay was one of a number I found some time ago; they are Ducommun
latching 12V SMA relays. These need a driver circuit which I made like this:
and that's built on the veroboard you can see at the front of the PA block.
The output lines do this when the PTT is grounded and then disconnected:
All I need to decide now is what to set the Bias voltage to on the PA - not
sure about that!
Throughout Miss Luna Cat has been supervising from a distance: