How did you determine the input impedance ? Tweaking or measurement ?
73,
Steve, N2IC
On 12/18/2019 12:29 PM, Bill McHugh wrote:
Problem solved! After much gnashing of teeth and scratching of head, I
discovered that the tube impedance of my GI7-Bs is actually closer to 150 ohms
per tube rather than the 100 ohms which everyone assumes it is. The input pi
sections were assembled at the factory and installed with no regard for the fact
that the tubes had a different load impedance. I wonder if someone decided that
the input SWR problem could be handled by running the radio's internal tuner?
As you know, doing that often causes the tuner to continually try to re-set
itself as SWR goes down, power out comes up as does SWR and so on. It sure does
not work with my K3-perhaps some other radios with slower responding tuners
would find this an acceptable solution.
Some tweaking, mainly on the input C has enabled me to get input SWR on all
bands down pretty close to 1:1 or 1.2:1 in a couple of cases and my K3 is happy
once again!
73 and Merry Christmas to all
Bill VE3NH.
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