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In a message dated 9/8/2005 5:56:31 P.M. Pacific Daylight Time,  
lncarman@swbell.net writes:
My  filament transformer didn't have a center-tap
so I improvised a B- by using  an artificial centertap made of diodes
connected
to each leg of the  filament's secondary.
This tube is NOT a directly heated cathode. It has a indirectly  heated 
cathode ... connection to the cathode is the outside heater  connection. This 
is 
where you connect the B- through a RF choke to the tube. I  found that any 
other 
B- connection to this tube will induce hum in the  transmitted signal do to 
the AC heater current ending up in series with the  cathode B-.
 
Terry W6RU
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