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Author Topic: W8JI NEUTRALIZING CIRCUIT FOR SB200  (Read 1887 times)
K2LGO
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Posts: 180




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« on: January 01, 2009, 07:29:24 AM »

W8JI-s page on amplifiers is one of the best there is, and on
http://www.w8ji.com/neutralizing__amplifier.htm
he shows a circuit for neutralizing a SB200 and similar  amps, but the connection marked STUB pla I don't understand...Can someone please clarify.  Just as Tom mentioned in his site, indeed my SB200 has the plate resonance, and maximum power at different points...BOB
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WB2WIK
Member

Posts: 21837




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« Reply #1 on: January 01, 2009, 09:37:47 AM »

It's a coupling "stub" aligned to couple to the plates of the 572Bs, so it's located in between the two tubes, usually soldered to a ceramic or teflon feedthrough, the other side of which is connected to the toroid installed below the tube bases at the filament connection.

Usually this is just a wire or a "tab" (maybe 1/8" wide, made of copper flashing or similar) maybe a couple of inches long sticking up in between the tubes and not touching anything, but having a soldered connection at its base where it attaches to the feedthrough terminal.

Possibly Tom has some photo examples.  He gets on this site pretty often.

WB2WIK/6
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