Re: Topband: Rig Comparisons

["Carl" <km1h@jeremy.mv.com>]

Feedforward, pre distortion, and conventional FB have all been around a long 
time in the analog world of amplifiers at audio and RF.
With digital it has become easier to implement the complex versions and is 
pretty much standard well into the 100 GHz range and beyond.
The USN and USAF in particular use it extensively in the EHF region. My last 
employer before retiring had me working in that region.
Carl
KM1H
----- Original Message ----- 
From: "James Wolf" <jbwolf@comcast.net>
To: "'Richard (Rick) Karlquist'" <richard@karlquist.com>; "'Michael St. 
Angelo'" <mstangelo@comcast.net>; <jim@audiosystemsgroup.com>; "'TopBand'" 
<topband@contesting.com>
Sent: Saturday, August 02, 2014 7:06 PM
Subject: Re: Topband: Rig Comparisons


> 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@contesting.com] On Behalf Of Richard
> (Rick) Karlquist
> Sent: Saturday, August 02, 2014 4:22 PM
> To: Michael St. Angelo; jim@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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