|[AMRadio] Re: AMRadio Digest, Vol 42, Issue 14|
ars.w5omr at gmail.com
Wed Jul 11 21:53:54 EDT 2007
Ron Lawrence KC4YOY wrote:
>>> Anyone got a HF Plate Modulated AM transmitter for sale in North
>>> Carolina. Hopefully the coastal area?
>> Grab a good ol' Johnson Viking II. They're floating around pretty
>> much everywhere,
> Saturday night we put the Viking II on the bench at w4zo's for a
> little check out,
> and got it working after finding about half the tubes had shook out of
> their sockets.
> 100 watts out with 300ma on the plate. It's loaded with AM crystals.
Typically, a pair of 6146's should probably only be loaded to around
220mA ~ 230mA *max*.
The manuals for the Viking Ranger, and Viking II's, and Viking Valiants
(all use 6146's in the final) say to load the final to 110mA, 220mA and
They -more strongly- state that grid drive should not exceed 2.5mA, 5mA
and 7.5mA, for the Ranger, Viking II and Valiant.
Just something to keep in mind, when you're loading the final.
A tip I learned a -long- time ago, from Fred/W5JKD in Priddy, TX (high
school chum of W5PYT) was to load the rigs 10 to 20mA -less- than what
the book says. 20mA is pretty significant as far as the impedance of
the final is concerned, and a difference of about 5 watts output (not
that anyone could tell), but -more room- for the audio to expand in the
plate of the final.
Best of luck with your find!
73 = Best Regards,
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