UHF 80 Watt PA, Modified NMT transmitter


This is not a homemade design ! only modified..
All the stuff in the other small rooms, osc. pll. modulation. drivers and so on has been removed
The PA gives 80 Watt out after the filter, at 28Volt powersupply and 30Watt input drive


It took 2 weeks to change it to give full power out,
it's not an easy thing on UHF 434Mhz, even the smallest leads can give problems.
I wanted to use this PA meny MHZ from the normal opperating frequency, so it was try and try again to get the gain and phase right..

The input stage is a 90 degree spliter, then the two power NPN transistors. The two outputs is then combined into one.
The internal phase needs to be exatly 90 degree to give max power out, so a few adjustments was done
This PA had no adjustments, no variable capasitors from the beginning, so I mounted a few the right place,
and changed a few of the caps on the in and output tuned circuits.