[AMRadio] Re: 4-65's

ne1s ne1s at neandertech.com
Thu Apr 5 15:34:03 EDT 2007

Geoff/W5OMR writes:
> Does anyone have any 4-65's? 
> I think that'd be a neat little ~100w rig to build up.. a single 4-65 
> tetrode, modulated by a pair. 
Sounds like a neat combination. You oughta be able to get about 150W carrier 
out of one, run less conservatively (not that anyone will hear the 
difference, of course). 

Someday I am going to build a rig with a pair of 'em modulated by 811s, when 
I get a round tuit. Already have the HV PS/modulator deck built, just have 
to do up the RF deck, which will also contain the VFO (a T-195 PTO I've been 
saving for this project), and RF and AF driver circuits. I hope to run the 
pair at 500W input (2500V @ 200 mA), or close to it, depending on the plate 
efficiency I'm able to achieve. 


> 6.3v @ 3.5a?  Got those transformers, too.  

Actually, they want 6.0V, so drop the voltage to the primary or run  
resistors in the primary or secondary circuits of the fil xfmr. One trick is 
to use appropriate lengths of undersized wire to the filaments (whatever 
length is necessary to drop the filament voltage at the socket to 6.0 V). 


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