[AMRadio] Re: Gates BC250L efficiency

K9AF at aol.com K9AF at aol.com
Thu Sep 30 00:45:05 EDT 2004

hello to all:
SUCCESS!!   I took a small file and carefully filed the enamel off the wire 
near the hot end of the IPA tank coil/ PA grid coil, then I attached a small 
piece of tinned bus wire to the end threaded connector post.  I then shorted out 
the first 9 turns of that coil with this small jumper. Of course retuning to 
resonance was necessary, and to be honest, it didn't change the variable 
capacitor a whole lot, nor did it increase the 810s grid drive more than 2 MA, BUT  
I now have achieved 73% PA efficiency, which according to the Gates factory 
manual is exactly what I should get, and what I was getting on 640 kc BEFORE I 
converted the transmitter to 1.885 MC.  
So now just a few more 'clean-up" items, and you'll hear me on 160 meters 
with full AM!   Thanks to all who made suggestions!


Jerry K9AF

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