[AMPS] Antenna tuner

[Tom Rauch]

> Now I have another question.  The schematic I'm following for the
> tuner calls for a 1700 pf capacitor, in series to ground, on the input
> link.

Current in that link capacitor system is always equal to the line 
current, so you can get the approximate current using standard 
power formula's in the Handbook and other places. I=sqr root of 
P/R, so current would be about 5.5 amps with 1500 watts.

Some doorknobs will handle that, some won't.

The voltage across that capacitor will be current above times Xc at 
the operating frequency, so you might have almost any voltage 
from a few volts to several thousand volts depending on how much 
C you use and the frequency. If you adjust the tuner so you use a 
lot of capacitance, voltage will be very low.

The vacuum variable will be a poor capacitor choice, because the 
link capacitor often has to be moved in value a large amount. It is 
also generally not critical to tune, because Q is often very low in 
the link. Use an air variable if you can find one, and when you 
adjust the tuner use the maximum C you possibly can.

    
73, Tom W8JI
W8JI@contesting.com 

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