[Amps] re: EBS at soft or quiet moments

[skipp isaham]

Are EBS circuits worthwhile..? 
-
I would venture to say there is little time where a 
radio driving an amplifier (combination) has no 
RF output in the transmit mode. Even quiet station 
transceivers have a minimal amount of RF output 
result from ambient room noise. 
-
Add some compression and the story gets 
worse. 
- 
The last Alpha EBS circuit I tested, required less than 
a watt to activate ("trigger"). 
-
(The standby/receive mode of a standard amplifier 
most often cuts off the cathode current, as does 
the EBS type circuit )
-
As quiet as I can be, my peak reading watt meter 
and scope often indicate some RF output most 
of the time... even between words on breath and 
room noise.  Is the EBS honestly helping much 
in linear mode operation when the input rarely 
falls below the control detector threshold in a 
typical amateur operation?  
-
I can see the case for CW operation, but 
most SSB operators are going to bias on 
during most any portion of the transmit 
mode where the EBS is supposed to 
pay off..? 
- 
What might I be overlooking...?
-
skipp
- 
From: 2 <2 at vc.net>
***  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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