>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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