Official Position on Adaptive Predistortion

It has been quite a while (years) since activity on this topic, and I am reading it in late 2022. I feel like I'm missing something. So here are some questions to help me fill in my noobie gaps. 

1) Isn't there a difference between Pre Distortion and Adaptive Pre DIstortion? 

If the amplifier is known in advance, it seems like all transfer function parameters are internal and can be known except the changes due to output load.

2) Is output load variability the one and only (complex) variable that requires the "A" in APD? 

3) And, can't match be detected during tuning (at least in a fully Flex system) ? 

4) If so, then although the matrix becomes large, can't the amplifier characteristics be entirely formulated in advance (output vs. input IQ, DC biases, load, temperature) ? 

5) Are people miss-using APD to mean PD? 

6) Do people want the radio to somehow learn an added non-Flex amplifier?  (therefore to Adapt)

7) Do any 6000 series radios employ PD for their internal 100W PAs now? (from what I've read, the possibility to implement APD is designed in but not implemented. Fine. What abiut PD?)

7a) if No, then are they so linear as to be comparatively acceptable if not superior to other 100W radios on the market)

8) Does the Power Genius Amplifier, when connected to a 6000 series employ PD? (I have seen a mention of an "IMD Pre-corrector" in a review, and I'm aware of the harmonic diplexer load). I have not seen a specification of 2-tone IMD for the Power Genius.

And finally a comment rather than a question. Problematic IMD is so obvious on the waterfall. And when I hear /see it it's always (so far) been a solid state power amplifier. And in general not noticed on tube amplifiers unless the station is having ALC problems. Not seen on a 100W barefoot rig. Now that is just my observation. If I am at least 50% right, then it seems that a solid state Flex power amplifier should have IMD reduction circuits. And PD is a way to do it very well indeed.

Thanks for your attention.

More about IC 7610:

https://forums.qrz.com/index.php?threads/icom-ic-7610-adds-digital-pre-distortion.878480/

Think about THIS 9 years later - nobody needs APD.

The radios themselves FAR exceed the distortion performance metrics. And if you can't design an amplifier that does as well, APD is not going to bale you out.

73

What amazing things have you accomplished in the last 9 years?

N4GA

No problem Mark, we'll just disagree.

First, this is Amateur Radio communication here. Most commonly SSB over HF, which by any real audio quality standard is garbage.

Knowing this, the FCC has NO spec for IMD, they instead suggest an acceptable bandwidth (3kHz). They however, do have an actual emission standard for harmonic distortion and this is -43dB from the fundamental.

So back to IMD - as long as your audio is not noticably distorted, AND your entire signal (all the IMDs) are inside the target BW (3kHz), that's all that is needed. You're officially not bleeding outside your BW.

And you can obtain this easily with the equipment that is currently on the market.

If you're overdriving your amp, using a really messy amp, or a really messy TX, then this is operator error.

Ever since APD was moved into the Amateur Radio arena by Apache Labs / Anan, that small group of users has taken on APD like a religion. Mostly because they were the only ones to have this so-called holy grail and nobody else did. Usually those people also have what they think are studio quality audio setups - all for really bad SSB audio quality. Pretty entertaining.

73

Rob

www.n4ga.com