As I recall, the Boonton 535A isn't specially made at all, but rather a selected 2A6 triode/twin diode. The tube is selected for having an especially clean vacuum, and being capable of running with a really high grid leak resistor (100M).
-Chuck Harris Bill Hawkins wrote:
A couple of other things about dealing with lightning: There is a cone of protection starting at the highest grounded point around for about 100 feet. These were developed to protect explosives bunkers from direct hits. The angle of the cone (between a vertical line to the tip and the edge of the cone) is 30 to 45 degrees. Exceptions have been reported, of course. That should save you from most direct hits. Then you have to deal with the electric field that builds up from passing charged clouds. Some kind of high-value resistor in parallel with a small glass sealed spark gap from antenna to ground would help. It doesn't have to deal with a direct hit, just keep the grid from arcing in the tube. Some of the sealed spark gaps also contain inert gas. You don't want a triggered spark gap, just a surge suppressor. Old radios with octal sockets had tubes in the RF and IF amplifiers with grid caps, like the 6K7. Should be a lot more available than the Boonton 535-A. Bill Hawkins _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
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