The Boonton (later HP) model 260A Q meter used such a tube for a 100 megohm VTVM. The tube was specially made for Boonton as the 535-A. There are also references to the 1659/535-A. If you search for it, use "Boonton 535-A" to avoid the Tektronix 535 scope. The Q meter manual has a picture of it.
Bill Hawkins -----Original Message----- From: Poul-Henning Kamp Sent: Wednesday, June 25, 2014 3:45 PM Somewhere, sometime, I saw an homebrew article for a lightning detector which was based on some obscure valve/tube that had grid on the top terminal. A wire from the grid electrode ran to a porcelain isolator and from there to the wire antenna, in order to get the highest possible imput impedance. I have no idea where I saw that article, but some HAM magazine or possibly Elector about 10-20 years back is a good guess. _______________________________________________ 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.