** The tradeoff with Carborundum/Globar ® units is that they have a bit
much intrinsic L for optimal VHF suppression service. To explain: To
exhibit good suppression, the inductances of the R and the L paths need
to widely different.
After experiencing problems with 10 meter operation on a 4-1000A amp
years ago (R-sup toasting) I ordered a suppressor direct from Eimac that
they used on all their Eimac-Varian RF generators. (2X4-1000A) It is made
up of a 120 ohm 25 watt Globar resistor surrounded by two turns of silver
plated quarter-inch copper tubing, 1 inch in diameter. After 25 years, I can
still read the printing on the Globar. The trade-off seemed to pay off. Eimac's
stock suppressor for their 3-1000Z is a 10 ohm 25 watt Globar, with two turns
of half-inch silver plated copper strap, tightly wound around the resistor, and
secured with clips. This allows quick checking of the R-sup value during
annual spring cleaning by just removing one clip.
I have used all of Rich's products at one time or another, and have had
excellent results with 3-500Z and smaller tubes.
There is a world of proven engineering and research out there which allows
us laymen to pick and choose the right components for the job at hand.
My fear is that with the passing of so many Handbook authors and the
"dumbing down" of the ARRL Handbook to a QRP manual, no one is
there to pick up the ball to document this legacy of knowledge for future
builders.
(((73)))
Phil, K5PC
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