[AMRadio] 833 AM rig

John Coleman jc at pctechref.com
Mon Feb 9 19:39:08 EST 2009

Ok here's the deal.  Otis runs a single 833 in the class C final and modulates with a pair .  The single 833A is in a circuit for push pull but only has the one tube in it. and only one nuetralizing capacitor and only one coupling capacitor to the ballanced tank with swinging link.  The grid circuit is a push pull tank but  any other typewill work  as it's only function is to supply the proper driver to the final grid.  The plate tank is a push pull balance type because the phase inversion for the neutralizing cap is accomplished by the ballanced plate tank.  The tank circuit is shunt fed to keep the DC and audio off of the tank circuit.  The center tap of the coil does have a RF choke but it goes to ground to insure that there is no audio or DC on the tank components.  He used to run about 3000 volts on the plates but after the AM power reduction thing he ran about 2500V at 200 ma.  I can pretty much draw the circuit but you may wish to consult the web page at

Please note that the circuits do not depict the shunt feed tank coil.  But I can draw that up if someone needs it.
The above web page has not been proof read by anyone that is good at it, so there may be some spelling, grammer and other mistakes in it.

John, WA5BXO

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