>From: Manfred Mornhinweg <manfred@ludens.cl>
>To: amps@contesting.com
>Subject: [Amps] Switching techniques - was SS amps watercooling - was
> PowerGenius XL
>Message-ID: <58B05C9F.6020407@ludens.cl>
>Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>Hi Doug,
> I have been poking around on Internet looking for a scholarly article
> or two on generating SSB using switching techniques for the RF
> generation.
>There is a lot of material out there. But not many practical circuits that
we hams could simply >copy.
A point of historical interest on this is the KAHN STR-84 AM Stereo exciter
and the Power-Side system (which used that same exciter). For stereo the
object was to upper and lower sidebands that were independent and could
carry the right and left channels of the stereo. Power-Side's objective was
to create just one primary sideband.
The late Leonard Kahn created this system to give him total control of the
output of a standard AM broadcast transmitter. Of course for this he was
not interested in eliminating the large carrier (at least not yet). The
exciter modified the envelope feed to the transmitter and phase modulated
the carrier with phase shifts on both. I don't know the details of the
design (Leonard kept this pretty close to his chest) but I know the system
contained an "inner transmitter" which was used in some way to make
corrections to the signal. Generally this could be thought of as a type of
pre-distortion, although since there was feedback it was not pre-distortion
in the traditional sense.
Incidentally, he created the first AM stereo system in 1959, and it was on
the air at (then) XEAK out of Mexico (FCC wouldn't let him on the air in the
states). This system required a rack full of vacuum tubes and wasn't nearly
as elegant as his later solid state designs. The idea was to offset tune two
radios. I played with this at the time, and it worked surprisingly well.
Sadly, the FCC opted to give FM the green light for stereo and not AM, and
the rest is history. Had they granted stereo to AM at that early date, who
knows how things might have transpired. By the time AM stereo was
re-introduced, the market window for stereo had passed and nobody cared
about it.
This is a bit off topic. If you want more please visit my web site at
www.chrishays.com <http://www.chrishays.com/> .
Chris AB6QK
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