"Richard Clark" wrote in message
...
On Mon, 24 May 2004 05:46:01 GMT, "Lord Snooty" wrote:

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

Hi Andrew,

You got me confused too.

Is the "load" the resistor, or the resistor-cap combination when you
measure these voltages?

You describe a voltage minimum across the load for a cap setting of
250pF; but you also maintain that the voltage across the load
increases for the variation in capacitance from 100 to 700pF which
contradicts the first measurement.

Further, the construction of a high power semiconductor does not lend
itself to supporting inductive reactances (the junctions are quite
manifestly capacitive in structure). By specification the device is
characterized as exhibiting 27pF @ 1 MHz (for 28Vdc although there is
not much variation until below 10Vdc). There are a world of other
variables to consider, but none portray inductance within the device.
This alone should provoke you to re-examine your premise.

73's
Richard Clark, KB7QHC

To clarify
a) "Load" in my context means "load resistor (r) and load capacitor (reactance
jx) in series"
b) The output transistor feeds to the output port through an inductor. One
would therefore expect X, the source reactance, to be positive.

Andrew