[AMPS] FUTURE SS AMP

[Jon Ogden]

>SAW A HIGH POWER, INEXPENSIVE SOLID STATE AMP DESIGN IN QST A COUPLE
>MONTHS AGO.  IT WORKS FB ON CW, BUT CANNOT BE USED ON SSB DUE TO
>NON-LINEARITY.
>    MY IDEA IS THIS:  BRIDGE A COMPARATOR/ CORRECTOR CKT TO SAMPLE
>OUTPUT, THEN MODIFY  INPUT, TO MAKE THE THING NEAR-LINEAR RESPONDING,
>USING SEVERAL MILLISECOND DELAY.
>   THERE IS A ROMANCE TO THE OLD TUBE AMPS, BUT ALSO BIG NEED FOR CHEAP,
>SOLID STATE POWER.
>    PLEASE LET ME KNOW YOUR THOUGHTS ON THIS.  CUD SAME COMPARE/CORRECT
>CKT NOT BE USED FOR TUBE AMPS, RUNNING NON-LINEAR, HIGH EFFICIENCY
>CONFIGS??
>    DOUG WALLER - NX4D

IMHO, yes you can do this sort of thing.  However, it isn't easy and can 
be quite complicated.  In my engineering days, I was part of a design 
team that developed several linear amplifiers that were for use with 
multiple carriers.  We used a technology called "feed-forward" to 
actually generate IM in a parallel path to the main amplifier, shift it 
180 degrees out of phase and then add it back into the main path.  When 
two signals 180 degrees in phase get added...BAMO! no signal.  So the IM 
effectively was eliminated.  That's a simple answer and not technically 
complete.  We were able to achieve IMR levels of -70 dBc or better 
running 150 Watts out with 16 carriers.  150 Watts might not sound like a 
lot, but it was at 800 MHz.

Linear Television amplifiers for HDTV also use this same sort of 
technology but on a much larger power scale.

Unfortunately, there was more software in our amplifiers than hardware.  
The software and control mechanism to do the cancelation was quite 
complex.  Yes, you could build a similar system and tweak it by hand but 
it ain't necessarily that easy.  The amplifier shown in QST was a Class E 
amplifier which is extremely non-linear.

Try it is my best suggestion.  If it works, then maybe YOU can write a 
QST article.

73,

Jon
KE9NA


-------------------------------------
Jon Ogden
KE9NA

http://www.qsl.net/ke9na


"A life lived in fear is a life half lived."


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