On 4/16/2013 8:37 AM, Chris Wilson wrote:
I am unsure if the antenna matching "stuff" in my Kenwood TS-590
exciter precludes the need for this, though? I am trying to match 50
ohms to near 50 ohms,which is the cathode impedance of the 3CX3000A7
valve, I guess the antenna matching unit in the Kenwood would do this,
if I just removed the stock Pi input on the Henry, but would I then
lose the desired "flywheel effect"?
If you don't have a tuned input circuit in the amplifier, then the return path for the RF
cathode current is through the coax and the transceiver output tank. This causes the
performance to be dependent on the cable length. It also might damage components in the
transceiver.
I am similarly confused by advice I have had regarding*measuring* the
stock 27.12 MHz input circuit in the Henry, as a test of my measuring
methods. I am advised to put a 50 ohm carbon composite resistor from
the cathode of the 3CX3000A7 to ground and use the AIM on the RF input
socket to the RF Generator RF deck to measure how it is now. But
looking at the circuit diagram of the Henry I see there are isolating
capacitors between the PI input circuit and the actual pins for the
cathode. Shouldn't the loading resistor be direct to the output side
of the Pi tuned circuit? If not I now have doubts over whether a dummy
load DIRECT to the output side of my own Pi circuit, on the bench, is
correct, or if it needs the de-coupling capacitor before the dummy
load?
The capacitor is probably large enough that it won't affect the results either way. It
won't hurt to put it in, though.
--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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