[Amps] PLATE RESISTENCE

[Will Matney <craxd1@ezwv.com>]

Chris,

The Q is of the tank circuit and is added in the formula after you find 
the plate impedance. You are correct that the impedance will be 1/2 of 
one tube. A Q of 10-12 is used for the proper action of the tank circuit 
as a filter for harmonics, etc. There's an Excel spreadsheet available 
at several websites for determining pi and pi-l tanks. I think Rich 
Measures has it on his website. Just input the plate impedance, the Q, 
and frequency, it will determine the Tune C, Load C, and L. Then for L, 
use the air coil formula in most text books. The coils wire diameter 
needs to be sized for the power out and the frequency to hold the Q you 
want. This wire size is in a chart in most ARRL and radio engineering 
books. You will see that the gage raises with the frequency. 12 to 10 
meters and up will use tubing for legal limit output. About 6 meters and 
up is where using a coil will stop and striplines are used.

Will Matney



Question,

In a 2 tube design the plate Z ohms are cut in half when in parallel
right? Another words the tube plate Z of 1100 ohms is now 550 ohms
correct? How about QO? I have a QO of 12, what would that be?

Thanks for the help

Chris
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