Jim,
Yes, the adaptive pre-distortion algorithm works very well when using SSB.
In my own use with Alpha amplifiers and an ANAN 200D, I see a 25 dB 2-tone
improvement in SSB mode, that results in -60 dBc 3rd-order products. SSB
shows no "head and shoulder" bandwidth on a panadapter.
To your point, the "memory effect" he describes in the presentation relates
to changes in linearity with device heating. LDMOS devices exhibit low
memory effect and are of course, the rage in SS amp design. Memory effect
manifests in dynamic IMD testing. For example, 2-tone testing may show a 25
dB IMD improvement of 3rd-order products but when observing occupied
bandwidth on a spectrum analyzer or panadapter, the real improvement is
compromised with dynamic heating changes to a transistor.
The improvement is also affected by RF signal leakages. The algorithm
adjusts for any non-linearity it sees at the RF input. That can be a
combination of the exciter, PA, and external amplifier. The goal is to
maximize isolation so that only the final RF source is sampled and
corrected. As such, I ended up making extensive mods to my ANAN 200D. A
pair of Dow-Key microwave relays are now responsible for RF signal
management. It's an RF-tight system from the Alpha amplifier's RF output
sample back to the ANAN receiver.
One consequence is that a lot of relays were chattering in CW mode. But
since CW doesn't require linearization, I wrote a small program that uses an
Arduino microcontroller on a custom PC board to sample the mode state. The
controller samples the mode and deactivates the unnecessary relays. The
ANAN is now completely silent during CW QSK operation. The custom PC board
can be seen somewhere down the middle of my QRZ page. The Arduino code is
also shown.
Paul, W9AC
-----Original Message-----
From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Jim Thomson
Sent: Tuesday, December 6, 2016 10:06 AM
To: amps@contesting.com
Subject: [Amps] Alpha 9500 vs. Acom 2000A questions
Date: Sun, 4 Dec 2016 09:56:48 -0500
From: "Paul Christensen" <w9ac@arrl.net>
To: <amps@contesting.com>
Subject: Re: [Amps] Alpha 9500 vs. Acom 2000A questions
Correction. The IMD improvement is closer to 20-25 dB for vacuum tube
amplifiers.
http://www.n3sh.org/Tech%20Section/PureSignal_final_selection.pdf
>"NR0V's pre-distortion algorithm can clean-up most any dirty amp by
>10-15
dB when the amp is included in the correction loop."
Paul, W9AC
## On page 39 of the above power point presentation...it sez...
... Probably difficult for modes such as SSB and AM....
## Does this concept work on ssb or not ?? It appears all the various
tests were done using a steady state 2 tone signal.
Jim VE7RF
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