noise burst on transmit

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  • Question
  • Updated 2 years ago
  • Answered

RE: original post:

https://community.flexradio.com/flexradio/topics/noise_burst_at_beginning_of_transmission

I do not believe this was fixed in the last release or two.   It appears that the tx audio buffer is filling while in receive, and a few hundred milliseconds of that buffer is being sent at the initial time of transmission. It appears that the tx audio buffer needs to be gated and/or delayed a few hundred milliseconds once PTT is activated.

For example, if I am listening to a QSO with the speakers, and they are obviously loud enough to open the audio gating of my tx audio chain, when I first key up, stations are reporting a noise burst at the beginning of my transmission. Using a headset is NOT a solution..........


Eric

K2CB


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K2CB Eric Dobrowansky

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Posted 5 years ago

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Tim - W4TME, Customer Experience Manager

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Eric - I have added your report to our bug tracker so we can investigate this further.  Thanks for the report.
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K2CB Eric Dobrowansky

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Has this been properly addressed in version 1.4?
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K2CB Eric Dobrowansky

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Will this be corrected in V1.4?
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K2CB Eric Dobrowansky

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?????
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Lee

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Maybe re-read Tim's post??

Lee

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K2CB Eric Dobrowansky

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I did read his post. That was all I heard. I've heard nothing further on the matter. Here or on the trouble ticket that I submitted months ago. I was hoping for an updated answer from flex regarding this issue.
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np2g

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YEP the transmit buffer fills up . As a interim you may want to use a downward ex pander or level clipping.

You also could use your head set instead of the speakers

I usually must adjust -36db threshold to defeat this effect.

Until its addressed .
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K2CB Eric Dobrowansky

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Has this issue been corrected in the upcoming 1.4 release?
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Ed.G, Software Engineer

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Official Response
Yes, I believe we fixed this issue in 1.4.
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K2CB Eric Dobrowansky

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Thank you for the reply, Ed.
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Ben Morris

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I am having this issue in a new radio I received yesterday. I'm also running 1.4.
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Tim - W4TME, Customer Experience Manager

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Do you have the DEXP enabled and configured?
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K2CB Eric Dobrowansky

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The downward expander should be irrelevant. A downward expander, or some sort of external processor with limiting or gating, is only masking the real problem. The radio should be gating the tx audio path until which time PTT is asserted, with some sort of buffer delay calculated in to compensate for the tx audio path's A/D delay.  I have not had a chance yet, but I hope to install V1.4 this evening and test this. I sure hope it has fixed the issue, as the release notes indicate.


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Ed.G, Software Engineer

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There are two issues here, one as K2CB mentions is the TX gating which we included in v1.4. If this is still a problem then we can re-open the issue to look at it.

The other, as Tim mentions, is the DEXP. If noise on keying is over the DEXP threshold it will open the DEXP temporarily and let through background noise until the decay time is over. This can look like a burst of noise but is different than the TX audio path gating. 
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Ben Morris

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Ed, you are correct on your assumption. It must be radio fan noise I am picking up. If I disable DEX, the noise is there but doesn't appear as a burst. I can get rid of it all the way by turning DEX all the up. However, the mic becomes more critical on direction it is spoken into. I am using a Heil Goldline GM5.
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Howard Koenig

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I am also experiencing this burst.
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Tim - W4TME, Customer Experience Manager

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We have several issues in our bug tracker related to this particular issue to investigate further.  Thanks for the report.
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K2CB Eric Dobrowansky

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Completely deleted prior versions of SDSR. Reset radio defaults twice, once before loading 1.4, once after. 

The noise burst issue still exists in V1.4

Eric

K2CB


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K2CB Eric Dobrowansky

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Any chance of this finally being corrected in version 1.5?
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K2CB Eric Dobrowansky

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Was this fixed in the V1 .5 release?

Unless I missed it, I did not see anything in the release notes.
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K2CB Eric Dobrowansky

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Will this FINALLY be fixed in V1.6?


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Cal Spreitzer

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It does not appear this issue has been fixed.  I'm using V1.6.21.159 and the burst is still seen and heard when using the stock Flex FHM-1 front panel mic in SSB mode.

N3CAL

   
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Doug K0DV

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I have this problem with a new Maestro using 2.1.9 version software... noise burst on transmit.  Dudley has had me increase the TX delay, and that help just a little.  But the TX delay coupled with the remote internet delay is killing me.  Because of the timing delay, working DX in a pile up is more than difficult.  I have filled out a ticket but have not heard anything in several weeks. The noise is heard using the stock Flex mic FMH-1.  The noise is worse when I feed a USB mic into the line-in input on the back of the Maestro.
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K2CB Eric Dobrowansky

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Will this ever be addressed?
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David Holmgren

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I transmit noise when I key the mike with my new 6400.  I'm running the latest version of Smart SDR.  Looks like from the previous posts this has been an on going problem for years.  Is there any fix or ideas to try.  David K9RUF 
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Lee

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How did you discover this??
No one I have talked to on my 6300, 6500 or now 6400 has ever complained I have noide when I key the Mic.
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Ken - NM9P

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If you are using a standard Mic input, this can be greatly reduced with proper adjustment of the DEXP (Downward Expander)   It will prevent random noise being fed into the audio chain while in RX mode that is dumped into the transmit buffer when you first key the mic. 

If you are using audio from your PC on remote, it is more difficult, because DEXP doesn't function in PC Audio mode.

Ken - NM9P
 
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Lee

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What?? Why would RX mode noise ever get put in the TX buffer.
That's a bug for sure.
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K2CB Eric Dobrowansky

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Seriously folks, this is a design flaw that needs to be corrected.

It was first reported over three years ago already.   Any suggestion to use a noise gate, lower the mic gain, or place speakers further away, is not the correct fix.

The tx audio path (and/or following buffer) should be gated prior to assertion of ptt. Just like any other ham radio transceiver. The other brand SDR radios do not suffer from this condition.

How about an official answer from Flex - will it EVER be corrected in software, or is it a hardware design issue? 

If it is indeed a hardware issue, that which carried over to the 6400/6600 series, then shame on Flex!

If we had some sort of schematic, we might be able to answer the question ourselves...........



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Ken - NM9P

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It isn’t RX noise, it is mic noise gathered while receiving. The slight latency between tx and RX gives just enough time for a slight noise burst in some cases. But, as I said, DEXP helps a lot. Also, being careful with mic gain settings helps..

It also got better when they implemented the changes in RX filter latency.
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Lee

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We DON'T want a work around we want it FIXED.....
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David Holmgren

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The DEXP is kind of nice.  You know sometime with some hams you hear a dull roar of background noise when the ham stop speaking the their mic is still keyed?  The DEXP takes care of that.  I tend to agree with you too that something as basic as this should be fixed. 
(Edited)
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David Holmgren

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...Well I’m in my 30 day trial so this may make me sent it back. Can’t believe this has been going on this long with no resolution. When I first experienced it I kept wonder what I did with this new radio not being familiar with it. I was even thinking this was something wrong with just my radio. Everything else is great with the radio but transmitting is as important as a great SDR receiver otherwise it will end up being on my desk as an SDR receiver while I use another radio that works reliably.

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David Holmgren

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OK got home and tried the DEXP and it's basically an audio gate that will turn off or gate the audio going into the radio.  I found the sensitivity and delay slider.  It seems to work pretty good but make me sound like I'm using VOX, cutting off the first part of my speech.  Not a big fan of that...
My problem with audio can't be helped with DEXP.  I think my radio may be defective if you watch the short video clip of what I'm experiencing.  The audio you hear of me is coming through the speaker of my KX-3.
If there's a fix for what the radio is doing on this clip please let me know.  David K9RUF
https://www.dropbox.com/s/fgm7kqxjhh11mjl/IMG_4380.MOV?dl=0
(Edited)
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David Holmgren

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Well here's an update to the above post.  First off the DEXP is more than a gate.  It appears to reduce mic gain and at the same time the sensitivity as to when your voice is heard.  Interesting.  Now as far as the noise goes the last time I experienced something strange with the Flex I unplugged the power in the back from the Anderson Power Pole vs. just cycling power from the front power switch.  After doing that this morning the noise problem seems to be gone.  So far so go.  I'll put the radio through its paces today see if it behaves.  David K9RUF
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Ken - NM9P

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DEXP is like a soft gate, not a hard switch. Adjusting it is like adjusting AGC-T., only backwards... using headphones and MON, key the mic with no audio. The slowly turn it from left to right until the background noise quits. If you want, go a little further if your local shack noise varies. But don’t go too far, or you will get a more abrupt gating effect.

RE: the power-off reset.... yes, this is often the first recommendation when things are acting strangely. Occasionally a power glitch, windows update, or DPC’s can foul things, requiring a reset. I always reboot both computer and rig after a firmware update, or before a major operating event like a contest or DX hunt....

Good luck. Glad things are working better. It is a great little rig!
(Edited)
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David Holmgren

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Well darn it the noise burst came back :(  Opened a support ticket...
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Lee

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ALL of us should open a support ticket right away!
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Bill -VA3WTB

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Is the noise burst transmitting were people mention it on air. I don't think I have ever seen that here.
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K2CB Eric Dobrowansky

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What?

Yes, people are hearing it on the air. That is the whole issue. The operator sitting behind the mic doesn't even know there's an issue unless the receiving party mentions it.

Most appliance operators will not even notice it. But skilled listeners will mention it every time.

Quite embarrassing for a $4300 6500, no less a $7500 6700.
(Edited)
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Bill -VA3WTB

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I see, I talk to people who are very critical about audio mostly because that is what we do when we get together on air. I will ask them to listen to me today and see what they hear.
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Bill -VA3WTB

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I was just talking to Dave W2OX. I did not hear anything on him and he said I was clean as well. But there is a problem that still can be corrected buy Flex. For the most part people are not having this problem, at least with the Flex radios I have talked to.

In my case I use a headset so this problem never happens. And it is clear that this problem can be corrected with with better operation of the radio. Such as turning speakers very low, use DEXP, close talk mics. Use headsets.
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Doug K0DV

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I submitted a ticket about this same issue when operating my Maestro remotely.  Dudley had me add TX latency, but no amount of latency corrected the problem. We had a QSO on 20 meters so he could hear the noise himself. Just received an email from the new Dudley, Mr. Neal Campbell... they are on the case.
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Lee

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Thanks for the update...Is Dudley gone from Flex??
I really like him!
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Jay / NO5J

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I like Dudley too, but having a spare Dudley, I like even better. Dudley might like it too.

#FlexRadio IRC chat

   73, Jay - NO5J

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Doug K0DV

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Dudley is retiring at the end of the month. His conscientious work will be missed.

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K2CB Eric Dobrowansky

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Correction - it's been four years since this was initially reported and acknowledged.

https://community.flexradio.com/flexr...
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David Holmgren

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Eric,

Just so we are talking about the same noise.  You said: "The operator sitting behind the mic doesn't even know there's an issue unless the receiving party mentions it."
If you watch my video you will see on the screen the broadband noise on your screen or at least I do on the 6400M.  It's constant and replaces the mic audio.  The receiving party will hear nothing but white noise.  Is this the problem that you have been experiencing for 4 years or is it different? David K9RUF.
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K2CB Eric Dobrowansky

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You appear to be experiencing a different issue.

This thread concerns the TX audio buffer as described in the original posting.
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David Holmgren

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Well still good news so I am cautiously optimistic.  The noise burst has not occurred since yesterday morning.  Putting the radio through its paces and it's holding up.