Improved Anode Circuit Parasitic Suppression for Modern Tubes

Posted on Feb 6, 2014

This is the unexpurgated, pre-edited version of the article `Improved Anode-Circuit Parasitic-Suppression For Modern Amplifier-Tubes` that appeared on page 36 in the October 1988 issue of QST. A more recent treatment of the subject appeared in the September and October 1990 issues of QST. The article is titled `Parasitics Revisited. ` The purpose

Improved Anode Circuit Parasitic Suppression for Modern Tubes
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in publishing this manuscript is to allow the reader to see whether on not QST is influenced by advertisers. To do this, open up a copy of the Oct. 1988 QST, and compare. Anything in parenthesis is not part of the manuscript text. The information in parenthesis was added later. The traditional copper-inductor/carbon-resistor anode [plate] parasitic-suppressor has been used in vacuum-tube amplifiers for at least 50 years. The earliest record of an anode parasitic-suppressor that I can locate was in a transmitter that was built in the early 1930s by the (Art) Collins Radio Company. (In late 1990, I was made aware of some interesting information on anode-circuit VHF parasitic suppressors in the 1926 Edition of The Radio Amateur`s Handbook. This information was inexplicably omitted from post-1929 editions. Info provided by Dave Newkirk, WJ1Z) Much of the reason for Art Collins` early success can be attributed to the fact that he, almost alone, understood that where RF is concerned there is no such thing as a zero-potential "ground" and that any wire or strap was a capacitor-inductor VHF tuned-circuit as well as a conductor. He understood that an "RF-choke" acted like a short-circuit at certain frequencies and that sometimes a resistor would make a better RF-choke than an RF-choke! Because he understood these "RF secrets", he was the first manufacturer to build a transmitter that: worked on all frequencies up to 14. 5MHz, was...

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