Ah! I've noticed this but never understood it. At least with the Globe Champ
350, the power output can increase quite a bit off resonance to the right, but
the plate current also quickly gets way out of hand. I prefer using it to using
my Orion II and my AL-1200 on AM, even though I suspect the Orion II may be a
bit cleaner.
Anyway, I just tried it and, if I'm careful and limit the plate current
increase to no more than 5%, the power output goes up just a wee bit faster
than I'd expect based on the plate current increase alone. I had always
secretly worried that the PA stage wasn't properly neutralized but, after very
careful neutralization, I still saw it. I've modded my Champ so that it uses
tetrode 8643s rather than the unobtainable pentode AX9909s.
When I followed this tuning, it was as the very last step in the tuning
procedure, so I made no changes to the loading once I'd set the plate current.
Have I got the procedure correct?
Kim N5OP
"People that make music together cannot be enemies, at least as long as the
music lasts." -- Paul Hindemith
> On Mar 1, 2014, at 21:02, "Bob McGraw - K4TAX" <RMcGraw@Blomand.net> wrote:
>
> I comes from many years of tuning AM broadcast transmitters. The "right side
> of resonance" refers to adjusting the tank circuit tuning capacitor to a
> slightly lesser value of C which is normally turning the knob to the right.
> One will notice a slight increase in plate current, otherwise a bit more than
> the current at the actual "dip" value. Typically about a 2% to 5% increase
> is adequate. For my RCA BT the dip is about 425 ma and I run it at about 435
> ma for 3300 volts DC.
>
> With this method one will notice an increase in output power when tuned to
> the "right side of resonance" by a few milliamps while tuning to the "left
> side of resonance" the same amount will show a decrease in output. The input
> power remains the same for both cases but the output is greater in one case
> and less in the other case.
>
> 73
> Bob, K4TAX
>
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