[AMRadio] AM Transmitter Advice??

W5OMR/Geoff w5omr at satx.rr.com
Sat Feb 18 17:32:47 EST 2006

Donald Chester wrote:

>> From: "Brian Carling" <bcarling at cfl.rr.com>
>> Hey - mount those 6AG7s upside down in cooling oil and you
>> can run 500 watts to 'em.  I wouldn't try it but I am sure
>> SOMEONE has, LOL!
> My very first plate-modulated AM rig back in 1959 used a single 6AQ5 
> to drive a pair of 807's as class-B triodes with screen and control 
> grids tied together with 20k resistors, and negative feedback round 
> the 6AQ5.  It would work for a few minutes, and then distortion would 
> start to creep up.  I finally figured out that the 6AQ5 was 
> overheating and the distortion was due to thermal runaway.  I turned 
> the driver stage, which was haywired on a separate little chassis, 
> upside down and let the 6AQ5 rest in a jar of water.  That kept it 
> just cool enough to keep away the distortion.  But I would, on the 
> average, overturn the jar of water at least once every time I tried to 
> use that lashup.
> Don K4KYV

John/BXO can confirm this story;

Gene White/WA5ATH(sk) had a plate modulated rig out in his garage, and a 
modulation transformer that made the awfulest racket of talk-back, when 
modulating the rig.  The rig worked well, except for that talk-back.  
Someone (probably Otis/SWK) said "maybe opearte with the transformer in 
a container of oil".  So, Gene did.  But (heh) he kept the oil in a 
styrofoam ice-chest..

The running, on-air, joke was "...what's the oil-pressure on your 
modulator, Gene?"

Mind you, this was also in the days when 'parts was parts' and who 
-cared- what something looked like, as long as it worked!  Therefore, 
several parts were scrapped from rigs that server a different purpose in 
their life, and afterwards, such things as meters that indicated 
"manifold pressure" were used as current meters, etc...  You know how 
home-brewers are.

Ah, radio was a lot more fun, back then :-)

73 = Best Regards,

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