[Amps] IMD & ALC's

[R.Measures]

>Hi Rich,
>
>> **  RF-actuated EBS is an idea that looks workable on paper but one
>> which doesn't work acceptably in practice because the EBS switches in
>> and out of non-linear bias during soft-syllables.   Synchronizing the
>> EBS with the RF-relays is clearly the best approach - even though it
>> requires two, additional wires from the transceiver to the amplifier's
>> RL Control circuit.   As I see it, even with a  radio that had no
>> overshoot and pristine IMD, RF-actuated EBS would still have the
>> problem of generating IMD (and harsh-sounding audio)  by rapidly
>> switching in and out of non-linear bias during soft-syllables.  
>
>Yep.  The Aussie amp maker, Emtron, is VERY proud of their EBS, 
>because it holds dissipation down.  

**  This is true for those who still use PTT.  However, many people 
(including me) currently use VOX and transceiver-controlled bias 
switching.    Whenever I stop talking, within a fraction of a second, 
ZSAC dissipation is zero.

>I have had quite a bit of 
>experience with these amps (several different DX-2's with the now 
>scarce-as-hensteeth 4cx1600b), and have experimented on-the-air with 
>setting the threshold.  When set as the factory suggests, on SSB the 
>best report I got was "your signal sucks!"  It sounded fine when I 
>backed the bias down to where the resting anode current was... guess 
>what!?... equal to the value with the EBS turned off!  It would be a 
>good energy saver on CW, RTTY, etc.

**  chortle.  In other words, when adjusted for minimal suckiness in the 
Tx audio,  RF-controlled EBS Increases average dissipation for SSB.  It 
still puzzles me why anyone would promote a T/R system where the 
bias-switching was not always in perfect sync with the RF-switching.
>
>There are many things I like about the Emtron amps, though.
>
**  As do I.    He seems to have done his homework on VHF suppressors.  
>
cheers, George