[Amps] door knob capacitors

[Glen Zook]

Basically, the other door knobs that I obtained for a VERY good price were 20 kV!  Definitely overkill.

I "solved" the problem by putting 2 0.01 mfd capacitors in series with the 1400 pf door knob fixed loading capacitor.  This got the effective value of the 1400 pf down to just under 1100 pf which, in turn, got the loading at 50 ohms impedance almost in the middle of the air variable range.  

Being that I am a firm believer in the principles of the conservation of my finances and labor ("cheap and lazy"), I had the 0.01 mfd capacitors in stock and therefore used them.  I do need a high voltage transformer that is just a little bit heavier than the one that I had in the junque box.  That one has just a 120 VAC primary and I prefer to run my linears from 240 VAC.  Also, the voltage is a bit lower than optimum and I want to eventually run between 200 and 400 volts more on the plates of the GI-7bT tubes.  However, I did use the linear this past weekend during the CQ 160-meter SSB contest and it worked very well.  The output was right at 700 watts which is a great improvement over my "normal" 60 to 70 watts output.

Glen, K9STH

Website:  http://k9sth.com


--- On Sun, 2/27/11, DJ7WW <dj7ww at t-online.de> wrote:

Why do you want at least a 10KV rating while the capacitors will not see more then 500V? More important is to select a RF doorknob with low TCC.