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Author Topic: tank capacitance  (Read 1945 times)
WA2JHS
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Posts: 111




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« on: September 14, 2008, 08:28:58 PM »

Hello to all,
I have a linear amp that has a pair of 813's. It was given to me long ago and finally had time to get this thing working, first the power supply was an issue, but now that is fixed. Now, it seems, I can't seem to load it up on 80 meters, the plate load capacitor is
fully meshed and it still wants more. It has an additional 600pf in parallel with it on 80 meters. Does this mean I need more inductance or less???
73
Bill
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AD4U
Member

Posts: 2543




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« Reply #1 on: September 15, 2008, 06:26:41 AM »

Assuming everything else is OK, it sounds to me like you need additional capacitance (more than 600 pF)in parallel with your loading capacitor, although I never built an amp with 813's.  Did you tune it into a dummy load?

Why not just cruise hamfests and find a larger loading capacitor.  They can be had for just a few dollars.  Most amps I built used around 2000 pF as a loading cap.

I would not mess with the inductor.

Being a homebrew amp (I assume it is HB) there could be other issues as well.

Dick  AD4U

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