"Richard Clark" wrote in message
...
On Wed, 26 May 2004 02:07:50 GMT, "Lord Snooty" wrote:
Hi Andrew,

a load capacitor value of 250 +/- 10pF (-j80 ohms @ 8 MHz) was found to
produce a
minimum in the total voltage across the load.
What was the voltage?

Load voltage lies in the 5 to 20 volt peak range, depending on the power
setting.
This minimum represented about a 15% dip.

Also, as capacitance was increased over the range 100-700pF, the voltage
across the load resistor
increased monotonically.
What were the voltages?

Again, a nominal value between 5 and 20 V pk.

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.

as the capacitive reactance falls, you note the voltage climbs, this
hardly requires an inductance to explain this. Simple divider action
serves quite well. You have since revealed the inductor buffered
output, but the data is still pretty skimpy to bless it as the major
contributor to source Z.

Agreed, but if I keep increasing the load C (decreasing the capacitative
reactance ), I will see a peak in the voltage across the load resistor, which
will only happen if a conjugate match is occurring.

What are you using to measure this voltage?

A scope probe set to 10x, which has an unmeasurably high DC resistance and a
capacitance of 22 pF (measured). It's a good idea to use the 10x, not 1x,
setting, since the latter contributes about 80 pF, and will change the AC
response of the circuit.

Best,
Andrew