[Amps] TP9383/SD1460 used in 70MHz PA

[Steve Thompson]

Dick wrote:
> First of all thanks those who replied to my question.
> 
> Indeed these transtors came from an old FM-broadcast amplifier.
> I just have some of them, and I want to try to use them on 70MHz.
> 
> 70MHz is the European 4m amateur band, which might become available in PA
> in the future. (soon??)
> 
> As 70MHz is 'only' 18MHz below FM-band, I thought it might be worth to try.
I'd expect them to work fine on 4 or 6m. As John said, the die might 
have been tweaked to give best ruggedness and efficiency in class C use, 
but that's unlikely to stop them being useable in typical amateur use 
where you're unlikely to see temperature or load VSWR extremes. You 
might have to experiment to find the right bias point to get linearity 
across the power range.

Going up in frequency can be a problem as the internal input matching 
works as a low pass filter, but going down 50% in frequency won't 
normally give trouble. Load VSWR tolerance reduces at lower frequencies. 
You can get more power and linearity if you push the supply up to 
32-35V, but they will be much more sensitive to any mistuning or glitch 
at the output.

Steve