[Elecraft] Mod for AM?

[N2EY@aol.com]

In a message dated 8/14/03 9:27:57 AM Eastern Daylight Time, 
elecraft@radions.net writes:


> I have a friend 
> with an old Johnson Thunderbolt and I bet it would work out fine.

oh mama, a T-Bolt! Let's see how well it would work....

IIRC, a Thunderbolt consists of a pair of grid-driven 4-400As with a pair of 
866As for power. It was meant for SSB and CW service back when the legal limit 
was 1 KW input (averaged on SSB) to the final plate. So the power supply is 
probably good for 1000 watts continuous duty. 

Conventional AM linear operation is no more than 35% efficient, so you can 
expect 300-350 watts output (carrier) in AM linear mode. The other 650-700 watts 
are burned up as heat. The pair of 4-400s has 800 W of plate dissipation so 
they will be OK. 

Remember that in conventional AM service the PEP is about four times the 
carrier, so you will get 1200 - 1400 W PEP out. That's about the same peak power 
you could expect in SSB service at 2000 W PEP input (1000 W average) - the old 
legal limit. 

Is it worth all that trouble for a 300-350 watt AM signal? You be the judge. 
Consider, however, that a Valiant (275 watts input, maybe 180-200 out) is less 
than 3 dB below that level. 

73 de Jim, N2EY

(who once ran a nice NC-173/122/Viking 2 setup)


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