Hi all,
I designed a switchble input pi-net for my 'two-holer' (a pair of 8877's). The
calculated Z is aprox. 23 ohms. The circuit is located close to both input
blocking caps and tubes. I tested this circuit with both tubes connected to
the sockets and a 23 ohms resistor cross to both blocking caps. I tuned this
pi-net for all bands. As source generator I used the MFJ Antenna Analyser 259.
All settings was nearly SWR 1:1 and I was satified. Later, under real power
conditions all values are away up to 2:1 and higher. I know my first test was
made under static circumstance and in the real world it works under dynamic
conditions. But I do have no chance to tune the network under operation
conditions (no possibilities).
Is there to go another way to fix it right under 'could conditions'? Otherwise
I have to make a new metal design to operate the input pi-net parts under
power conditions.
Maybe it would be better to test this circuit with more r.f. power than the
MFJ 259 produces???
73, Werner DJ2HZ
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