Pre Distortion

  • 1
  • Question
  • Updated 3 years ago
After listening to the Anan's with pure signal, Flex can take all the time they want bringing it in. I don't like the audio on most of them and I find they mostly have the same sound. There is something not natural. Could be just me, but that's my opinion.
Photo of Bill -VA3WTB

Bill -VA3WTB

  • 2317 Posts
  • 529 Reply Likes

Posted 3 years ago

  • 1
Photo of Paul Christensen, W9AC

Paul Christensen, W9AC, Elmer

  • 313 Posts
  • 132 Reply Likes

Whatever distracting artifact you're hearing, it is not caused by the PureSignal pre-distortion algorithm.  

Paul, W9AC

(Edited)
Photo of Peter Bentley

Peter Bentley

  • 74 Posts
  • 25 Reply Likes

Here we go again.

We know it works well in Commercial cellular and for sure its needed on our crowded narrow bands, so lets just get on with it and implement it as soon as possible, thankfully its progress.

To make a judgement on another manufacturers product in such an undefined and casual way is irrelevant.

Most of us want Flex to be the best, so lets be a bit more scientific and precise before we criticize next time please.

G4BIM

Photo of Jon - KF2E

Jon - KF2E

  • 620 Posts
  • 179 Reply Likes
Peter,

I agree with you that PureSignal is a great technology and will ultimately help with crowded bands. However, the reality is that it won't have any meaningful effect for decades. Hams are cheap and as a group are going to spend as few $/watt they can. Older radios that are not capable of this technology aren't simply going to get replaced to help clean up the band.

I too want Flex to be the best, but I can think of a big list of stuff I consider more pressing than PureSignal.

Jon...kf2e
Photo of Peter Bentley

Peter Bentley

  • 74 Posts
  • 25 Reply Likes

Yes I am in broad agreement with you Jon.

What is it they say, 'A journey of a thousand miles starts with a single step'

Personally I may lobby our UK Radio Authority 'Ofcomm' to put all manufacturers of short wave Ham radio equipment on notice, that as from say 2020, all new manufacture Ham transmitters used in the U.K., confirm to tight IMD figures, which may force them to include some form of 'Pure Signal' in their fundamental design.

The genie is out of the bottle and for good sound common sense reasons.

After all, we have good legislation in the civilised world for all sorts of manufacturing and products, maybe its about time we tightened up on the HF spectrum and its proper use.

Its a valuable and powerful asset which we are privileged to be able to use freely and should not be abused.



(Edited)
Photo of Jay / NO5J

Jay / NO5J

  • 1401 Posts
  • 209 Reply Likes
What is it they say, 'A journey of a thousand miles starts with a single step'
Or with a single stagger. Remember many of them are old. They wander about aimlessly, having a poor sense of direction,  They do appear to have been on the journey for a long long time. 1000 miles? yeah could be.

You can get them to stop, place a shiny object in front of them, tell them about it's low low introductory price of $19.99, and the limited time offer that include 2 shiny objects for the price of one. The money back guarantee, if returned within 30 days, and stop them dead in their tracks.

Remember folks PureSignal uses only the purest ingredients! We select only the finest signals.
(Insert the standard legal disclaimer promising a chance at every malady known to science and possibly death.)

And they will form an orderly, but somewhat crooked line.

Will we ever learn? We haven't yet!

Yes Please! Flexradio  Add PureSignal and all the other " Oil of Snake" miracles I read about on my IntarWebs machine.

The preceding was typed into my PureTypeTM USB keyboard, so you know it's all pure.

Pure what?

 
73, Jay - NO5J
Photo of k3Tim

k3Tim

  • 816 Posts
  • 155 Reply Likes
An interesting observation Bill, thanks for your comments / observation. Interesting replies as well! 

"The proof is in the pudding"  - if audio doesn't sound good something is amiss.  Granted it may not be due to pre-distortion (PD) or perhaps the implementation of PD needs a tweak. Would have expected the developers of PD on the other vendors box to have tested on the air signals with / without PD to verify no audio degradation.  Haven't seen test results - can anyone share a link?

I'm all for the PD, would even pay US$ for the feature, but think there are other items of priority before PD, specifically release of 1.4 / noise filters.  Obviously, 1.4 is the train that is about to pull into the station and the filters would be nice but in my local not a must have.

Bear in mind the cellular systems (GSM / CDMA / LTE) are all digital transmissions whilst SSB is analog.  I would expect PD to play well with SSB but maybe it doesn't.....

While on the subject of PD, the cellular folks are moving even further ahead with envelope tracking (ET):

https://www.qualcomm.com/videos/qfe1100-worlds-first-envelope-tracking-technology-3g4g-lte-devices

Basically, ET reduces the DC voltage to the final PA when the RF crest is lower so the PA runs at a more efficient level. The DC voltage to the PA adjusts to a level to match the level where the device is most efficient. This is similar to the old school AM plate modulators I believe. I would suspect this would reduce IMD products as the PA is operating in a more linear region but haven't verified this in any references on ET.

ET in combination with PD should make a ultra-modern / clean / efficient PA.  The downside to ET is the complex / cost of the PA power supply (which is not in our 6K boxes).
Photo of Bill -VA3WTB

Bill -VA3WTB

  • 2317 Posts
  • 529 Reply Likes
Dave, WO2X and I were talking about my observations. He said PS seems to remove an harmonic in voices that we are used to hearing, taking away from the natural sound we are used to hearing.

If Flex brings in PS I hope they can fix this, But it is likely just a part of how it works. Other wise we will all mostly sound much the same.
Yes Peter I am ready for another finger smacking for making another opinion comment.
Photo of Barry N1EU

Barry N1EU

  • 495 Posts
  • 121 Reply Likes
A lot of nonsense intermingled with good comments posted here.  Listen and judge for yourselves whether Pure Signal degrades the audio quality:

https://www.youtube.com/watch?v=TtbNBHhVqeo
https://www.youtube.com/watch?v=HUu-CRmplIw

The ssb sub-bands would be transformed if all manufacturers of dsp hf radios made the decision to implement adaptive pre-distortion in a timely manner.  Amp manufacturers should start providing an attenuated output (BNC) for pre-distortion use by the exciter. 

73, Barry N1EU
Photo of Bill -VA3WTB

Bill -VA3WTB

  • 2317 Posts
  • 529 Reply Likes
Yup just as I said, on the second one it was a removed harmonic with PS switched on, interesting.
Photo of Barry N1EU

Barry N1EU

  • 495 Posts
  • 121 Reply Likes
Bill, could you please describe at what time in the recording you noticed this and what harmonic do you hear being removed by Pure Signal?

https://www.youtube.com/watch?v=HUu-CRmplIw
(Edited)
Photo of Bill -VA3WTB

Bill -VA3WTB

  • 2317 Posts
  • 529 Reply Likes
As soon as he said PS is back on, much of the depth was lost, anyways this is not a debate just my observation. There have been a few of us noticing this and we were just kicking it around.

I have know idea what harmonic is lost but we hear it.
Photo of Barry N1EU

Barry N1EU

  • 495 Posts
  • 121 Reply Likes
What you're hearing is the lack of microphone proximity effect immediately after I switch Pure Signal back on.  There's about 10 seconds of audio after I switch Pure Signal back on and for the first 5 seconds, there's a lack of proximity effect and then for the next 5 seconds the proximity effect is there again.  I probably moved my head while speaking.  Pure Signal is not removing harmonics or otherwise degrading the audio.

Barry N1EU
Photo of k3Tim

k3Tim

  • 816 Posts
  • 155 Reply Likes
Hi Barry,

"A lot of nonsense intermingled with good comments posted here. " 

I fail to see any nonsense, can you please educate us to clear up the nonsense, providing links for further study would be helpful.
Photo of W1AEX

W1AEX

  • 12 Posts
  • 9 Reply Likes
I remember when I got my Flex 5000 being told that one of the best things about the Flex was all the adjustments you can make, and one of the worst things about the Flex was all the adjustments you can make. It was a funny thing to say and very true. The point is that setting up any SDR is a big part of the fun but the opportunity for operator error is great. Pure Signal will not correct that problem and you will hear and see evidence of that on the bands all the time.

There's a lot of "cargo-cult mentality" about TX audio settings and a lot of monkey-see monkey-do chatter about what the settings should be. The truth is that if your audio sounds crappy without PS it will sound crappy with it too. The other truth is that without PS running the typical transmit audio THD hovers around 3% and with PS engaged the audio THD drops to around .2% so I believe Bill when he says he can hear the difference. I hear it too and like it very much. It would be inappropriate for me to post links to reviews of the ANAN radios in the Flex Community so email me if you want a link to a technical review.

Meanwhile enjoy the Flex 6.xxx radios that are on your benches because they are quite awesome and they sound beautiful! I look forward to having a new one sitting on my operating desk when the time comes.  73,  Rob W1AEX
Photo of Mike - WB8CXO

Mike - WB8CXO

  • 54 Posts
  • 12 Reply Likes
Well said Rob... Thank You for all the help you have given SDR radio operators from all camps!
Photo of Paul Christensen, W9AC

Paul Christensen, W9AC, Elmer

  • 313 Posts
  • 132 Reply Likes
Barry,

If you have the time, it would be interesting to post the same video (or even better, just an audio clip) but change APD every 15 seconds for say a 90 second duration.  Only this time, don't identify when APD is on/off.  Just announce when the switch occurs. 

To make this even more interesting, announce a switch for one transition, but don't.  If a video, mask the spectrum display.  It would be interesting to see how well folks score among those who claim the presence of audible APD artifacts.  

Paul, W9AC
Photo of Barry N1EU

Barry N1EU

  • 495 Posts
  • 121 Reply Likes
Sorry Paul, I didn't make the video nor was I aware that I was being recorded during that xmsn.  

Barry N1EU
Photo of Peter Bentley

Peter Bentley

  • 74 Posts
  • 25 Reply Likes

Well done Barry

Thank you

Photo of Ned K1NJ

Ned K1NJ

  • 301 Posts
  • 75 Reply Likes
       It improves the -signal- not necessarily the -audio-. 

Ned,  K1NJ
Photo of Barry N1EU

Barry N1EU

  • 495 Posts
  • 121 Reply Likes
Yes, I think that's the point Ned.  I don't think it affects the audio.  I would guess that the algorithms involved work outside the audio passband - on the sidebands  (but I'm just guessing).  I'll try and ask the engineer who coded Pure Signal and report back.

Barry N1EU
Photo of Barry N1EU

Barry N1EU

  • 495 Posts
  • 121 Reply Likes
Okay I stand corrected: "When you turn on PureSignal, it cleans up the IMD INSIDE the passband as well as the IMD outside the passband.  As a result, with PureSignal ON, the output is a MORE ACCURATE representation of the audio input to the radio."

Barry N1EU
Photo of Steve W6SDM

Steve W6SDM

  • 615 Posts
  • 279 Reply Likes
"Them thar single sidebanders is gonna ruin ham radio, Ahm here to tell ye!  Ain't nuthin' ever gonna sound as good as AM."

An quote from many QSOs heard in the 1960s. 
Photo of Rick Hadley - W0FG

Rick Hadley - W0FG

  • 554 Posts
  • 118 Reply Likes
I'll buy some of that PureSignal once they start packaging in a red plastic bottle and making it smell good like Marvel Mystery Oil!  I bet then I'll be able to stop worrying about elephants getting into the shack too. ;-)
Photo of Jay / NO5J

Jay / NO5J

  • 1402 Posts
  • 209 Reply Likes
Ok I Judge this entire thread, so far, to be lacking in the usual PureSignal FanBoy whingy attitudes.

Useful discussion, Good information for once.

As long as PureSignal is included in SmartSDR 1.X or SmartSDR 2.X for the previously agreed upon charges ie. Free\$199.00 USD ..., then my preference is that it gets included in a 1.X release. If they want to hold off until SmartSDR >2.X to debug and fix PureSignal then that will just make me more likely to buy SmartSDR >2.X even sooner.

But I may hold off, and save my funds for a Flex >6700, and SmarterSDR, and PurerSignal. I don't even know what I'm doing right now, much less what I'll be doing in the future. I suspect I may never know such things.

73, Jay - NO5J   
(Edited)
Photo of Bill -VA3WTB

Bill -VA3WTB

  • 2317 Posts
  • 529 Reply Likes
I don't know either Jay, PS is not a deal breaker for me. If it ended up as a purchase I don't know if I would bother with it to be honest. I see many Flexes on air and their signal goes right down to the very bottom, nothing on the other side band, to me that's pretty good and I know it won't bother anyone close. But then I have seen a few where they were not set up correctly and did not look so well. All depends how we run our radios, if set up well they are very clean.
Photo of Jay / NO5J

Jay / NO5J

  • 1402 Posts
  • 209 Reply Likes
Bill
I have some Flex friends too, Some of them have the cleanest signals you'd ever want to see, some of them need to be reminded to turn down (off) the rack gear. They know they sound better with it on,
look how much money they spent. They are "special".

73, Jay - NO5J
Photo of Bill -VA3WTB

Bill -VA3WTB

  • 2317 Posts
  • 529 Reply Likes
What can ya say Jay.  Lol
Photo of Alan - KA4B

Alan - KA4B

  • 107 Posts
  • 11 Reply Likes
I think that reducing power to the level needed for good communication might do as much good as adaptive predistortion, ----and it doesn't cost anything.