[AMPS] Input matching experiment

[Jim Strohm]

Hi

The latest swapfest yielded up an old ultrasonic generator with an 812A.
In my stacks of comic boo^H^H^H^H^H^H^H^H^H ARRL handbooks, I find a
reference that the input impedance of a cathode-fed 811A / 812A is approx.
300 ohms.

Has anybody ever tried using a broadband matching transformer, the kind
used in solid-state amps?  I'm thinking that a 1:4 transformer would give a
satisfactory match to 50 ohms; I'm probably going to experiment with a 1:9.
My idea is not to present a perfect match to the exciter, but to get close
enough that an SS exciter in the 5-watt range is happy on 10 to 40 meters,
which is a nice spread for the parts that came with the unit and the space
I have for a pi network.

Simplicity is the key.

Under load, would the cathode impedance swing higher or lower?

Any comments/words from experience?

Jim N6OTQ



--
FAQ on WWW:               http://www.contesting.com/FAQ/amps
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com