You should use separate tuned input slug coils for each bank as Ameritron
does.
-----Èñõîäíîå ñîîáùåíèå-----
Îò: Istvan Bogyo <bogyo@ph.debrecen.hu>
Êîìó: amps@contesting.com <amps@contesting.com>
Äàòà: 21 ôåâðàëÿ 2000 ã. 17:20
Òåìà: [AMPS] GS-35 (=8877?) Amp input
>
>Dear Friends,
>
>I traded in my FT990 to an FT1000MP recently, and have lots of problems. My
>home-made amp does not have a tuned input, and the SWR of the input is far
>from good on multiple bands. This results in the autotuner of the "MP" is
>running all the time, even if I change the freq by a few Hz.
>
>The amp is made with a russian GS-35 tube (similar to an 8877) and
currently
>the input "cicrcuit is a single 5000 pF capacitor connecting the input to
>the cathode of the tube. I have tried other values, with little or no
>result. I have tried to install a 2:1 inpedance xformer, no result.
>
>I have tried to use an external tuner between the rig and amp, but it takes
>then three to five minutes to tune everything on changing the bands.
>
>Since it is an older amp, very little space is provided for a tuned input
>circuitry.
>
>Does anyone have a guess, how much the input impedance of this tube might
>be?
>
>Is there a "magic" method to match it to my "MP" without trying to build in
>a 2x9 position Yaxley switch and separate PI circuits for each band? All
>this in a 1x2x3 inch space...
>
>Is there another solution for this?
>
>Please E-Mail me direct at bogyo@ph.debrecen.hu
>
>73 Steve HA0DU
>
>
>
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>
>
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