[Heath] More SB-200 joys...long...

[Kenneth G. Gordon]

On 14 Jan 2012 at 14:59, Guy Giacopuzzi wrote:

> Assuming the 47 ohm resistors are the plate parasitics, and they're
> that different in value, I'm curious how you can have almost full
> output?  I'm used to a 200' giving me about 600 rf out.... Guy...

Remember that those resistors' only purpose is to load the coils to 
make them more broad-banded, and that the resistors are essentially 
shorted for DC by the parasitic choke coil.

Therefore, their difference in resistance has no effect on the 
voltage reaching the tube's plates.

What the difference in resistance shows is that one or the other of 
the tubes is exhibiting a serious oscillation at some VHF frequency, 
heating the coil, and cooking the resistor.

My SB-200, when everything is working correctly, and with new finals, 
in CW, outputs 750 watts on 80 meters, 700 on 40 and 20, and 650 on 
15 and 10, withOUT "overdrive". I.e., with grid current well under 
100 mA.

Ken W7EKB