[AMRadio] Re: AMRadio Digest, Vol 42, Issue 14


Geoff/W5OMR 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.

Ron,

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 
330mA, respectively.

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,
-Geoff/W5OMR




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