[Amps] Ameritron EBS-1 in AL-1200?

[Steve Katz]

The electronic bias switch circuit may cause additional IMD during soft
syllables, but in normal Ameritron amplifiers it does not cause any hot
switching of T-R relays because the amplifier remains "keyed" as long as the
key line signal from the exciter is present.  It only switches bias between
"near cutoff" and "operating," but the T-R relay contacts, both exciter and
amp out sides, remain keyed the whole time. -WB2WIK/6

"Success is the ability to go from failure to failure with no loss of
enthusiasm." -Winston Churchill

> -----Original Message-----
> From:	2 [SMTP:2 at vc.net]
> Sent:	Wednesday, July 30, 2003 2:27 PM
> To:	Dan Levin; AMPS
> Subject:	Re: [Amps] Ameritron EBS-1 in AL-1200?
> 
> >I'm pretty clueless about such matters, and would appreciate any advice.
> >
> >What do folks think about the importance of, and/or utility of,
> installing
> >the
> >EBS-1 electronic bias kit in an AL-1200 that is going to see heavy duty
> >contest use?
> >
> >At the risk of demonstrating to the world my complete lack of
> undestanding
> >of high power amplifiers, is it correct that this kit basically senses
> input 
> RF,
> >and biases the tube to cut-off in the absence of input RF - thus reducing
> the
> >"circulating currents"?
> 
> ***  With no input RF, there is always zero RF circulating current, no 
> matter what type of bias switch is used.
> --  .  When SSB RF drive  drops below the EB-switch threshold level 
> during soft-syllables, the amplifier switches in and out of non-linear 
> bias.  This results in more IMD during soft-syllables.  Another problem 
> with RF-actuated bias switching is that there is no headstart for the 
> amplifier's RF relay contacts to close before RF arrives.  This results 
> in hot-switching the RF input relay and the RF output relay in the 
> amplifier.  For AM and FM modes, RF-actuated bias switching does not 
> switch during soft-syllables, so there is no added IMD, although the 
> hot-switching problem still exists.  
> >
> >Thanks!
> >
> >            ***dan, K6IF
> 
> Rich, AG6K, 805-386-3734, www.somis.org / new e-mail adr r at somis.org
> 
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