After some investigation I have found that there is a time varying gain of some sort from the microphone to the modulation output.? It is worse at lower frequencies but can be seen at all frequencies.

This plot shows a 165Hz tone in white and a 170Hz tone behind in red.

Zoom in on 170Hz


Here the envelope was extracted from the above data and plotted as dB from the mean signal amplitude.? Additionally, there are measurements of 250 Hz and 2.5 kHz.? You can see that the period of the modulation is not the same for each tone frequency I tested.? I do not know if it is related to the audio frequency or if the modulation frequency just drifts around.? In any case, my frequency response test just happens to be grabbing points off of this envelope and it was displayed as ripple vs frequency when in fact it is ripple vs time.?


I will play around with various mic gains and input levels to see if I can learn anything.? Also, the hand mic has a 220k resistor between the mic input and the base of a NPN transistor that acts as a switch for the power inside the hand mic.? I will try loading the mic line with a resistor to see if it somehow impacts the mic input.

Hmm... Just thinking, I should be able to see ~5Hz AM sidebands on these ~170Hz audio tones.? I hope it is not some sort of power supply stability issue in my radio.

Franco, i have rebuild the Kernel and was able to make a? FT8 QSO.

So i think FT8 works now.

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Again, thanks for your and all the others Work to make the x6100 better. ?

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73 de Markus, DB2ZW

Ah thanks I got you done and working?

73

KQ4WGS

Under the Gen button, Volume page 3 - last button on the right is MONI - turn it down to zero.

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I am sorry for my bluntness but what do you mean by turn off the monitor

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73

KQ4WGS

Turn off the monitor.?

I am having some terrible issues when I Key the mic it come out form the speaker high pitch any help would be appreciate I am loving this firmware.

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73

KQ4WGS

Turns out that the problem with FT8 TX not sending out any signal was due to this line in the sun8i codec module in the Linux kernel:

Once I commented that line out, I could hear the typical FT8 sound coming out from the speaker, and I could see it on the waterfall.

It looks like that line was added to the sun8i code as part of this commit:

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I just pushed the patch to fix that issue to the X6100 buildroot version 2024.11 repo:

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Markus,

when you have time, please run a 'git pull', rebuild the kernel, and let me know if FT8 TX works for you.

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After this issue is confirmed fixed, I'll start working on a GitHub workflow to create an SD card image similar to Georgy's, so others can try it too.

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73,

Franco

Did you ever find a solution to this?

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I have the same error.

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Side note: FT8 WSJT-X works

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73

I've always heard the tale as starting with a stone rather than an axe, but so applicable in many contexts! I have been known to relay that story when discussing feature creep with new in career software developers.

On Sat, Dec 28, 2024 at 12:24 PM, Dan Wertz wrote:

Now, that would be very cool if we could have custom TX audio filters!

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On Fri, Dec 27, 2024 at 10:47 PM, Georgy Dyuldin wrote:

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As far as I remember, biquad filter is used there. I'm not 100% sure, but looks like coefficients are precomputed (stored as a values within firmware). I wonder to extract them and to apply to some test signal on computer. Perhaps, it will be possible to design a filter with better parameters).

--

Georgy // R2RFE

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Now, that would be very cool if we could have custom TX audio filters!

I initially thought so as well. ?I did measure the function generator, and it was extremely flat.

But after looking at several runs of the test using different drive levels, you can see that the ripples change run to run. ?Also, for the green trace below I cranked up the number of points in the FFT I am applying to the demodulated audio and there is a distinctly different pattern.? Tomorrow I will look closer at the demodulated waveforms to try and ferret out what is happening.? Hopefully it is something stupid in my test and not a "feature" of the radio

On Sat, Dec 28, 2024 at 02:36 AM, Dan Wertz wrote:

I found a 10uF tantalum cap I used as a DC block.? The 0.18uF I used previously was introducing some additional roll off.? I also changed to acquisition code to actually look at the FFT bin that has the signal.? Previously I was just taking the max of the entire FFT, but there is significant in band noise that was limiting the measurement floor.

I am not sure what is up with the fast passband ripple.? I may have some measurement issue.? Right now, I am trusting the function generator to be flat.? I will get a DMM on it to make sure.

It might be due to digital filter design on the firmware. At least, when I recorded signals - they all have some audible resonance close to cut-off frequency for any frequency from 160,200, 250, 300 Hz.

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As far as I remember, biquad filter is used there. I'm not 100% sure, but looks like coefficients are precomputed (stored as a values within firmware). I wonder to extract them and to apply to some test signal on computer. Perhaps, it will be possible to design a filter with better parameters).

--

Georgy // R2RFE

I found a 10uF tantalum cap I used as a DC block.? The 0.18uF I used previously was introducing some additional roll off.? I also changed to acquisition code to actually look at the FFT bin that has the signal.? Previously I was just taking the max of the entire FFT, but there is significant in band noise that was limiting the measurement floor.

I am not sure what is up with the fast passband ripple.? I may have some measurement issue.? Right now, I am trusting the function generator to be flat.? I will get a DMM on it to make sure.

Thanks for this!? I am planning on connecting a nice microphone and footswitch to the X6100 and started doing some testing.? I noticed the 300Hz lower limit on the audio and searched to see if that was typical of SSB radios.? I stumbled on this thread, and I agree it sounds much nice to my ear with the 160Hz lower limit.? Though I am reading for DX contacts the below 300Hz does not really add anything to intelligibility.? I measured the frequency response of my radio tonight using your patched firmware and this is what I got.? I did have a 0.18uF DC block between the function generator and the mic input, so it is possible some of the low frequency roll off is from that. ?I have not measured the mic port input impedance, so I can't say.? I will track down a 1uF and remeasure to see if anything changes.? I am thinking I will have a couple EQ settings programmed, so I can have a pleasant sounding preset and a punchy sounding preset for poorer conditions.

Watch out for those balls !? re the leg that is ....mine does not have any so going to order, size is 2.38mm.

Now? Possibly the best firmware/base version thread ?Joao, CT2HME?? the screen shot of the firmware he has stored.

Is there any help in that section.

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There is another way that may help, this does mean taking radio apart & you are warming to that, lots of video's.

Check the voltage on the back up battery.? Disconnect the main battery, press & keep pressed the power button,reconnect the PSU, this is with the sd card in.

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Way before the above what program are you using to burn the card.? You have also tried a brand new virgin card. ?

Hi Keith. Yes, external power. Warming up to taking it apart, watched a few repair videos so know what to expect.

Simon??

That's right you don't? get much confirmation of what's going on.

Has the radio ever been apart. And you are doing the fw upgrade with external psu,say 13.8v connected. Are you happy enough? to take the radio apart.

The APP firmware the one that you see erasing and loading. There is no visual feedback on the Base upgrade which occurs after system/upgrade button pushed (except a perecentage).