Re: Replacing BD139 with 2SC1969 or equivalent RF Transistor
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The biasing would need a little alteration but it should work fine as is. It also depends of course on what tcvr you are altering.
What will get the most gain is isolating the finals from their original supply voltage and increasing that from say 12v to 24v.
Since you are on this forum I expect you are using CRkit products. The spectral output is not great on these products, but they're built to a price point and simplicity.
If you really want to do a good job, dump the original finals and build a daughter board using your silicons.
It's really a chore of diminishing returns, those transistors are expensive compared to the BD139 and although you can push your output a little higher, 12w as I remember, there are cheaper easier options.
Try look for a design you can build outboard, maybe with a push pull circuit or doubled up finals.
Good luck, Nigel de ZL1NAY
On Mon., 30 Dec. 2019, 9:15 am Nicholas Triantafyllou, <nicholas.triantafyllou@...> wrote: