Date: Thu, 3 Oct 2013 10:17:33 -0700
From: "Dave Hachadorian" <k6ll.dave@gmail.com>
To: <amps@contesting.com>
Subject: [Amps] Tune cap at minimum
I have an amplifier that tunes up on 21 MHz with the tune
capacitor at minimum value. It acts like the capacitance should
be even lower for max efficiency and output on 21 MHz. All of
the other bands, 10 through 160 are fine. The output network is
a pi-L, and the tubes are a pair of GU-74b's.
I was thinking of squeezing or spreading the coil turns on the 21
MHz inductor closest to the tube, but I can't find the dang
formulas to figure out which way to go.
Any ideas?
Many thanks.
Dave Hachadorian, K6LL
Yuma, Arizona
## Spread the turns apart a bit. Then the uh will be reduced. Then you will
need MORE tune and load C.
Your problem is you have too much uh on 21 mhz. 10m band is fine..so dont
touch the 10m coil.
Just tweak the 15m coil very slightly... not too much. Just barely enough so
it will tune.
Jim VE7RF
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