"Richard Clark" wrote in message
...
Hi Guys,

I trust both of you appreciate the difference between a vaguely
described system and trying to fit a spec sheet to it. Far easier to
proceed direct from one or the other, but making a fit between the two
is like stepping from one boat to another with a high chance of
standing on neither.

73's
Richard Clark, KB7QHC

There are uncharacterised components surrounding my MRF136, and I'd rather
determine their lumped behaviour with the transistor than unsolder them one by
one and try and predict the answer. But that's because I think it's possible
to determine what's going on. One reason I *don't* think this is the following
little bench test this afternoon - with the load jammed directly on the amp
output; no cable, no VSWR meter.
At 8.000 Mhz and a load consisting of 50 ohms carbon 10W 10% in series with a
capacitance trimmer bank, at an output power level of about 2W, a load
capacitor value of 250 +/- 10pF (-j80 ohms @ 8 MHz) was found to produce a
minimum in the total voltage across the load. Also, as capacitance was
increased over the range 100-700pF, the voltage across the load resistor
increased monotonically.

The latter is easy to explain (it means the source reactance is positive, and
smaller than +j28.4 ohms), but the former is beyond my ken.

Best,
Andrew