Transmited signal corruption

  • 3
  • Problem
  • Updated 5 years ago
  • In Progress

Issue:
The quality of the transmitted signal, using any mode, declines over a period of time - typically within about two days of continuous operation.

For example: a single-tone (JT65-HF) digital mode TX signal will, immediately after booting the radio, will be sound (on an external receiver), look on the SmartSDR panadapter and appear on a spectrum analyzer as expected. The signal will degrade to something noisier and broader in, at most, two days of continuous operation and much faster when used in a complex (e.g. multiple panadapters) manner.

Receiving seems unaffected.

Mitigation:
Rebooting the radio (and restarting SmartSDR as a precaution) restores the system to nominal condition, but eventually degrades again.

Severity:
Relatively high, as I normally leave radios on for months (collecting spots, etc.) and I will invariably have to reboot the 6700 before attempting transmitting, taking several minutes.


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Mike - N8MSA

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  • Annoyed

Posted 6 years ago

  • 3
Photo of Ed, K0KC

Ed, K0KC

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Mike,

I also normally run my 6700 24 hours per day. I currently operate almost 100% JT65 and JT9 using WSJT-X. I do not listen to my audio and normally have just one panadapter open. A screen shot of a normal JT65 transmission on the panadapter is as follows:



Although it is difficult to see (click on the image to enlarge), the first "artifact" is about 60 dB down from this signal peak. After two or three days of continuous operation, the "artifact" moves up and is only about 20 dB down with a significant broadening as you mentioned. The only way to clear this anomaly up is to re-boot the 6700. I will do a screen capture of the anomaly the next time that it occurs and post both so that a comparison is possible. If I had not monitored the transmitted signal and attempted to operate under these conditions, I probably would have been spewing "garbage" all over the band. This particular screen shot is from 10 meter operation, but I have seen the effect on other bands as well.

Ed, K0KC
(Edited)
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Ed, K0KC

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Mike,

My degradation seems sudden rather than gradual as you mentioned.

Ed, K0KC
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Tim - W4TME, Customer Experience Manager

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Official Response
We are aware of this issue and are currently investigating it.  It is in our bug tracker.  Quality issues like this do get our highest attention.
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Duane, AC5AA

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Hi Tim - I'm curious if this is the same situation that is shown by Rob Sherwood's spectral purity measurements of a FLEX-6700 and posted in a PDF on the following page link, below his positive remarks about using the 6700 during a 160m contest:  http://www.dj0ip.de/transceivers/sherwood-xcvr-tests/flex-6x00/  I know in other fora it has come up as one of the poorer performers in that regard.  (not trolling, just concerned.)  Thanks!

  Duane, AC5AA

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Tim - W4TME, Customer Experience Manager

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Duane - We do not believe they are related.  We suspect it is an issue with intermittent buffer corruption in the DAX driver that is feeding digital audio to the radio.  We are investigating this.

BTW, Rob's comments were based on very old (as of now) SmartSDR software. It has gotten much better with v1.2.1.

Also his comments about having to use two computers is not a global truth, but is specific to his setup.  Using a single quad core or beter PC with twp sufficiently large (> 23") wide screen monitors works just fine for contesting.
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k0eoo

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Tim, can we get an update on this issue being fixed yet or not in the current SSDR 1217?
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Tim - W4TME, Customer Experience Manager

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The update is the issue of spurious artifacts when running DAX is still in the bug tracker.  I can't commit that it will be addressed in the upcoming SmartSDR.
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k0eoo

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That's OK Tim, I just wanted to know if it had been already fixed...  I can wait...
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Bob Wright, N7ZO

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Just to add some more information to this:  The DAX transmit distortion also occurs here with 1.2.17, usually after running DAX for 24-48 hours.  I find that I can fix the problem by simply disabling and then re-enabling the DAX channel (pressing the blue channel number on the DAX panel twice).

Here is a picture of the distorted signal while transmitting a tune signal from WSJT-X:


And the good signal after stopping and starting the DAX channel:


And a wider picture to show the scale (both pictures above are at the same vertical scale):


(Edited)
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Ed, K0KC

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Bob,

Your screen shot of the distorted waveform looks a lot like what I reported 4 months ago (see reply to you initial post). I promised a screen shot myself, but I stopped running the 6700 24/7 and have not seen the problem appear again.

Ed, K0KC
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Michael Alexander

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This is exactly what I saw, on the SSDR GUI and on the spectrum analyzer. I do run mine 24/7 (8 slices feeding 8 instances of WSJT-X), so this is a relatively significant issue for me.

Mike - N8MSA
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Mike - N8MSA

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Everyone - 

This is still occurring under SSDR v1.3. Is there timing on a fix, or can I provide anyone at FRS with additional information to help determine root-cause and remediate this?

Mike - N8MSA