Official Position on Adaptive Predistortion

W2PP

Gerald:
   I'm still hoping you will comment on my post above regarding the orphan problems????
Peter

N8SDR

Actually John running radios below there rated power output can at times cause the IMD to be worse than if run at or near full power.

David Decoons, wo2x

I tend to notice the single LDMOS amps are pretty bad with IMD as you start running near rated output. The SPE 1.3 & 1.5k, Acom 1200s for example. Simon Brown (Ham Radio Deluxe fame,) sent his 1200s back since it was bad with IMD. I think Acom has made some changes since. The dual LDMOS amps (Flex PGXL, KPA1500, German kit amp) are a lot cleaner due to the headroom. The 6600 running with low cut at 100 and Power Genius XL is very acceptable. Not APD clean but well within acceptable limits. Based on reports I get on IMD levels, I would rather Flex continue with development of features to improve my enjoyment of using the radio. Dave wo2x

Bill -VA3WTB

The radios has many under the hood tweeks done since that old test that effect IMD performances. Most Flexes I see now can have an IMD as low as -40

Bill -VA3WTB

That is true Dave, If Flex were in trouble with IMD performance. They would not have put APD on the back burner.

Gene - K3GC

The Question, IMO, isn't whether Flex is in trouble without APD (I feel definitely that Flex is quite healthy).

The main question is how much market would Flex gain with APD?  Also, a cleaner signal is good Ham citizenship.

Bill -VA3WTB

Two things come to mind.
First, I don't think they have lost a lot of market share,,Flex radios offer so much that they sell because of what they do,,and what they can do in the future. Flex has things no other company has.
And the same question can be asked about all ham radio companies, Icom for instance has two SDR radios out without APD and are doing just fine without it. And they don't seem to plan on it ever.

Secondly, Flex radios are very good ham citizens because they are one of the cleanest radios on the market. -40 is really good, so bothering others is not an issue,,unless the radio is setup poorly.

And considering the engineering put into the Flex amp to make it really clean shows their commitment to clean signals.

Nigel

I think out of band transmissions is mandated by everyone not just the FCC. or has the licence changed that much?

WQ2H - Jim Poulette

I see Wayne's point, the present numerical standards do present a fairly low bar. And while it really sounds cool from a philosophical perspective - it reminds me of that old idiom of "gilding the lily".

CFR Part 47 §97.307 (a-e) (Emission Standards) do however stipulate emissions limit criteria for radio apparatus put in service after 1 JAN 2003. It's definitely worth at least looking over: http://www.arrl.org/files/file/Regulatory/March%208,%202018.pdf

73
Jim, WQ2H

Rick Peterson

Howard, KY6LA

For an example of the benefits of APD for an amateur digital mode, see:

http://www.qsl.net/wa6nut/PureSignal

This link shows the FreeDV+ signal before and after activating PureSignal (FreeDV plus Video is a multimedia HF mode combining digital voice and video, employing 66 subcarriers total).

Without APD, this mode would produce unacceptable splatter on adjacent frequencies.  So APD is being applied to amateur digital modes with great benefit.

I'm looking forward to FlexRadio's implementation of APD.

Regards, Rick, WA6NUT

AC9S

The latest QST has an excellent article by Rob Sherwood that should be a call to action on predistortion.  Hopefully the market will respond to this the way it did to Rob and the ARRL's focus on receiver performance over the last 10 - 15 years or so.  Some SSB signals I see during major contests look like the pyramids of Giza on the waterfall.  I know it will take a while to cycle all the old poor performing transmitters out of use once good ones begin to appear, but we will never get better if we don't start.  I would think predistortion would be a competitive advantage.

Keith - AC9S

Stan VA7NF

Some contesting stations (CW and SSB) intentionally produce dirty signals - because it keeps other stations away from "their" frequency resulting in better reception.
As long as there is an advantage of dirty signals taking "poor performing transmitters out of use" will not happen.  On CW it also makes a more noticeable signal, and in many cases more readable.

AC9S

Yeah - I know.  It is a really poor practice and I suppose if we were to be true to principle we would avoid working those guys - at least in S&P.

HCampbell WB4IVF

According to Flex noise mitigation and pre-distortion are #1 and #2 customer priorities, per Flex’s comments on the customer priority survey results: 

 “…. the survey was very helpful in revealing the relative importance of noise mitigation and pre-distortion. We have heard these messages loud and clear and have already begun discussions on next steps to make improvements in these areas of performance.”

 So there is light at the end of the tunnel for those of us who would like to see progress in these areas, although I’m still a bit disappointed that Automatic AGC-T in some form didn’t make the cut. 

Howard

Mark K1LSB

What "survey"?  I was never aware of any survey..

Bill -VA3WTB

Were have you been Mark, that is all people talked about for weeks on here. The survey Flex invited us to fill out?

Mark K1LSB

Let me repeat, what "survey"?  I received no invitation (or any notice at all, for that matter) from Flex or anyone else.

HCampbell WB4IVF

https://community.flexradio.com/flexradio/topics/did-you-take-the-flex-survey

Mark Erbaugh

I think contest organizers should recognize this practice and penalize this kind of behavior. Until they do, if a dirty signal gives a station an advantage, why wouldn’t a competitor have a dirty signal? After all, if your goal is to “win,” why wouldn’t you do everything within the rules (and even slightly beyond so long as you don’t get caught) to give yourself an edge?