I mentioned yesterday that after retuning my vertical I had a 
diabolical swr at the shack end. That turned out to be because the pa 
was going unstable when it saw a 50 ohm load!!!

I have now done a few changes to the pa to hopefully get round this 
problem. The T50-61 toroid I had used for the pa output coupling 
transformer wasn't really up to the job and was getting hot. I have 
replaced that with a 26mm 3C85 toroid from my 136 stock and 
reconfigured it to be an isolating transformer which gets rid of a 
nasty series coupling capacitor. I have also done a couple of changes 
with the decoupling. My website has the updated circuit. It now seems 
to be stable and also putting out a bit more umpth.

My antenna tuning exercise yesterday has certainly got it one 
frequency (maybe a little on the low side as it is 50 ohm resistive 
at 501kHz and rises to 67.8ohms slightly reactive at 504kHz). 
Excellent SWR!

It obviously has worked as I have just had a (slightly scratchy) chat 
with G3UNT followed by a nice QSO with Mike G3KZU in Oxford. Brian 
has never heard me before!

73 Dave G3YMC

http://www.davesergeant.com