Topband: Rig Comparisons

[James Wolf]

It really doesn't matter how much power the amplifier is outputting.   A
simple explanation is that a sample of the output is inversely fed back and
combined with the input.   As was mentioned before, this method has been
around for a long time.  When you fly into an airport, the FAA radios that
the towers use have a Cartesian loop that does just this and these are 100
watt amps.  You wouldn't normally need that on AM, but the current day FAA
radios were designed to send 64 QAM data, so linearity is a must.
It's not new or difficult, but it does cost more.  

Jim - KR9U 

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Richard
(Rick) Karlquist
Sent: Saturday, August 02, 2014 4:22 PM
To: Michael St. Angelo; jim at audiosystemsgroup.com; 'TopBand'
Subject: Re: Topband: Rig Comparisons

>      * The 2014 ARRL Technical Innovation Award went to Warren C.
> Pratt, NR0V, of Santa Cruz, California. Pratt was cited for his 
> research leading to the development of PureSignal, "an adaptive 
> baseband pre-distortion algorithm used to improve the linearity of 
> amplifiers and reduce intermodulation distortion products emitted by 
> software-defined transmitters."
>
> Mike N2MS

 From the little I can glean from this description, it sounds like what
Agilent has been doing in test equipment since the 1990's.  At Agilent, it
is only good for a 10 dB improvement and assumes a "memoryless"
amplifier.  I don't see how pre-distortion is going to work on a high power
linear that has a significant temperature and load impedance fluctuations.

Again, this is based on the summary given, so maybe there is more to it.

Rick N6RK
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