Forgive me if this has been already asked, but I cannot seem to find the answer. My QMX+ is showing some signal every 500Hz in USB mode (and in DIGI mode) on RX. I hear it in the headphones as a light tone or series of tones a little louder than the static. My Yaesu FT-710 doesn't hear these tones when connected to the same antenna. This morning I made another MFSK144 contact with the QMX+ with a station I had just contacted on the FT-710. Same set up, same antenna, only difference is the radio used. The FT-710 was "hearing" the MSK144 signals, but they were light. The QMX could not "hear" the same signals, the "birdies" were louder than the signal. Almost as if AGC was adjusting to the birdies and not to the background noise. Here is a screenshot of the waterfall in WSJT-X showing the birdie signals. Notice the fairly solid lines every 500 Hz and the not quite as solid ones every 250 Hz.

?

?

I see the "birdies" on every band, but they get more pronounced the higher the frequency is. At 40m they are barely there, at 6m very obvious. Does anyone know what they are or how to get rid of them?

Erik,

My QMX+ began having similar, though not exact symptoms after a lot of experimenting with configuring in the new beta SSB firmware. I don't know the cause yet, but, out of curiosity, how are you powering your QMX+?

--

73, Dan - W2DLC

I have a Pyramid PS9KX 13.8V 5A supply that I am currently feeding through a 12V buck converter to keep it at 12.0V. I have also tried with my station supply (JetStream JTPS31MA) adjusted to 12V output instead of the standard 13.8. Same result with both of them.

So that eliminates the power supply as the source of interference.

--

73, Dan - W2DLC

On Mon, Mar 31, 2025 at 09:00 AM, Erik Larson wrote:

My QMX+ is showing some signal every 500Hz in USB mode (and in DIGI mode) on RX.

This is also happening on my QMX+ in Digi mode into WSJT-x.

So it should have nothing to do with AGC or with the SSB update - ?the SSB firmware should not have changed the Digi signal path, excepting some bug, and AGC is not in the data path in Digi mode, nor is any of the audio output or microphone wizardry.?

?

Their amplitude is quite low, even on 6m where they are most prominent - but in my case, the positions of the birdies are somewhat different on the lower bands except 10m.? I can reduce the amplitude a bit by touching or messing around with the 6m BPF and LPF, but they are still there, with the ones at 1500 and 3000 most prominent by far.? And they are there at the same amplitude even with a dummy load and different power supplies, so their source seems likely to be internal to the QMX+.

I'm just wondering if they might be the reason it seems "deaf" on MSK144 mode, since there is a birdie right at 1500 which is the center of DF frequency in MSK144..

I hear mine most on LSB. The sound changes on USB, and it's an on and off tone that repeats. I can hear them from 17 meters to 6 meters, and strongest on 12 meters. They seem to have gotten worse/stronger the more I mess with the configuration.?

--

73, Dan - W2DLC

On Mon, Mar 31, 2025 at 02:41 PM, Daniel Conklin wrote:

I hear mine most on LSB. The sound changes on USB, and it's an on and off tone that repeats. I can hear them from 17 meters to 6 meters, and strongest on 12 meters. They seem to have gotten worse/stronger the more I mess with the configuration.?

--

73, Dan - W2DLC

I didn't notice it in digi mode before the SSB beta.

--

73, Dan - W2DLC

On Mon, Mar 31, 2025 at 11:44 AM, Daniel Conklin wrote:

I didn't notice it in digi mode before the SSB beta

I see it on a QMX+ I haven't yet updated with the SSB beta, maybe with a bit lower amplitude; are you sure it wasn't there before?

Stan,? Yes, I'm sure about that. After I read reports of that I checked for tones and birdies. I found a few birdies here and there, but not these tones. They also were not there at first with the SSB software, but appeared after I started experimenting with band settings and calibration. I noticed the case got very warm after about 2 hours of trying different configurations, and then at one point I got a high pitched, very loud screech on one band. I noticed these in and off beeping noises after that, and it seemed like the birdies became more noticeable too. Something changed.?

--

73, Dan - W2DLC

I have the issue too since before the SSB FW release.? It has been suggested (by Jeff Moore here /g/QRPLabs/message/136646) that this issue could be PCM1804 related.? I bought a replacement but then life and complications from eye surgery have so far prevented me from attempting to swap it out.? FYI.

?

I think it can be corrected with filters or settings somehow. When I change to DIGI mode on the QMX, a lot of these noises disappear. In the image below, the bottom portion was DIGI, the top portion USB on the QMX+ (Pressed the Mode button just as green line appeared to change to USB RX)

Whatever filtering or settings are different between USB and DIGI, the RX looks a LOT better in DIGI. Notice the lines at 750, 1250, 1750, 2250, 2750 are non-existent in DIGI. The lines at 500,1000,1500,2000,2500,3000 appear unchanged by this, but there is definately something different between RX in DIGI and USB.

?

In this picture, I cycle back through USB to LSB. The bottom half is USB, the top is LSB.

Notice that when I switch between USB and LSB the tone or noise at 1500 and 3k both become more pronounced (stronger signal indicated by line turning red instead of yellow) Also the lines at 500 and 250 get stronger (solid yellow instead of broken yellow). Earlier today the LSB side was showing a pulsing tone at 750 almost like carrier from CW, but not in any CW pattern.. I did not get a screen shot of that while it was happening, but I now suspect it may have been an external signal. Note that all these signals I am highlighting are with the radio connected to a dummy load with a 36" piece of RG-8x

That pulsing signal like CW is what I get too, so I don't think it's external. It doesn't change with tuning, so it seems like something getting injected into the audio.

--

73, Dan - W2DLC

That confirms what I thought. It still seems like there is something firmware that could change how this behaves. Was just hoping there was a quick, easy solution. With these here decoding MFSK modes like MSK144 and VARA becomes difficult unless you have a strong signal, and MSK144 is a weak signal mode to begin with.?

GPS module causes the pulsing tones in mine too.

Unplugging it clears them, but obviously not best solution!

Im going to try decoupling the power local to it when I get the chance, and see if this helps, maybe someone else has tried this?? Perhaps some form of screening, GPS right next to the antenna input…

The fixed “birdies” I thought were mostly due to smps and Hans will enable (in due course) some sort of active frequency switching to keep any out of the band in use.

?

Rowan.

?

Yep, I second that. I discovered exactly the same thing. The GPS module generates CW like pulses. It goes away with out it.

?

For me, it was more obvious on the higher bands with wider filter (digi mode) and didn't really notice it on the lower bands.

Another observation on mine was that there is an awful lot of noise on 6m band with digi mode set and just a dummy load.

I have attached two audio file samples. One with GPS connected and one without GPS connected, both on 6m in digi mode, on dummy load.

?

Mel. M0KMD.

Mel,

Yours sounds a lot worse than mine does! You can definitely hear a solid tone, though, with or without the GPS. With the GPS there is the on-off code like tone under the other solid tone. My QMX high band does not have either of these tones, but my QMX+ seemed to begin having them after I installed the SSB Beta firmware and started experimenting with the band edges over the course of a couple of hours. I think something in the audio line became more sensitive to interference somehow.?

--

73, Dan - W2DLC

For some reason I cannot get audacity to record from the QMX.. But WSJT-X sees it fine (yes, I closed WSJT-X first before trying Audacity). So no audio recordings but another picture. Mel, mine sounds very similar to yours.

?

?

I have confirmed that the pulsating tone noise at 1Khz was from the GPS module, as with it removed the noise at 1Khz is markedly reduced. I will run it this way in the morning and see if it is better able to decode MSK144 without that persistent pulsating noise at 1KHz. I still see less of these noise lines in DIGI mode than in either USB or LSB, so I think there is something different with the RX audio? in DIGI that might help with USB also if I can figure out what the difference is.