Slight ticking sound

fapuc
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Joined: Sat Nov 21, 2020 12:49 pm

Helicopter background TX noise in DMR mode

Post by fapuc » Sat Nov 21, 2020 1:02 pm

Good morning,
problem with Baofeng DM5RPLUS
in DMR correspondents hear background noise like helicopter blades, it seems the fast switching unfiltered slots. It doesn't happen in analog FM and not even with original firmware.
Regards
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kt4lh
Posts: 152
Joined: Sun Jan 12, 2020 4:27 am

Re: Helicopter background TX noise in DMR mode

Post by kt4lh » Sat Nov 21, 2020 2:28 pm

If you're using an external hand mic, that's common, and unlikely it would matter if it was the original firmware or OpenGD77. If you're not using a handmic, odd, never heard of this (typically called 'motor boating' from the noise) just using the HT directly.

VK3KYY
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Re: Helicopter background TX noise in DMR mode

Post by VK3KYY » Sat Nov 21, 2020 11:13 pm

This does seem to happen on some radios.

But we have no idea why it happens.

Possibly these radios have hardware fault, and some difference in the way the official firmware samples the audio means the official firmware doesn't have this problem

fapuc
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Re: Helicopter background TX noise in DMR mode

Post by fapuc » Sun Nov 22, 2020 12:32 pm

Yes, the official firmware doesn't have this problem,
and it does not depend on radiofrequency reentry, because it is also tested with 50 mW and resitive load as an antenna, with HotSpot.
Regards

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EB3AM
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Re: Helicopter background TX noise in DMR mode

Post by EB3AM » Thu Nov 26, 2020 8:49 am

I have an original radioditty microphone, which does this effect. The problem is not with the device and less with the firmware.
The problem is the poor quality of the microphone that picks up the TDMA modulated rf, which makes a pulsating effect. If you decrease the power the effect is attenuated.

Don’t blame the radio, and the firmware.
Jordi, EB3AM, Talarn JN02ke, Catalonia.

Radios: OpenGD77 RadioDitty, Icom 7300, mcHF clone QRP,
Repeaters: MMDVM with a Standard RP80-U (DMR + FM), MMDVM + Motorolas (DMR+FM), Hytera UHF DMR+FM repeater.

VK3KYY
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Re: Helicopter background TX noise in DMR mode

Post by VK3KYY » Fri Nov 27, 2020 6:53 am

When I investigated the problem, the noise was on the signal from the microphone, inside the radios.

A few radios seem to have this problem, from the internal microphone.

I don't know how the official firmware deals with the radios which have this hardware problem.

Possibly they have some sort of software noise gate on the input signal which blocks the audio samples which contain the noise, but because non of my 5 GD77 radios, or my RD5R or my DM1801 do this, I don't know precisely the signature of the noise, and hence I can't write code to attempt to filter it

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EB3AM
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Re: Helicopter background TX noise in DMR mode

Post by EB3AM » Sat Nov 28, 2020 9:49 am

Hi Roger
Surely the pattern will be the same with the internal or external microphone, possibly only vary the intensity of it.
This pattern will have to do with the TDMA frame in terms of frequency.
So I think if it works for an external mic, where it’s easier for it to appear, it will also work with the internals.

I don’t know if you can observe the noise with an external microphone, but I think that’s the way to see it.
Jordi, EB3AM, Talarn JN02ke, Catalonia.

Radios: OpenGD77 RadioDitty, Icom 7300, mcHF clone QRP,
Repeaters: MMDVM with a Standard RP80-U (DMR + FM), MMDVM + Motorolas (DMR+FM), Hytera UHF DMR+FM repeater.

VK3KYY
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Re: Helicopter background TX noise in DMR mode

Post by VK3KYY » Sat Nov 28, 2020 8:42 pm

EB3AM wrote:
Sat Nov 28, 2020 9:49 am
Hi Roger
Surely the pattern will be the same with the internal or external microphone, possibly only vary the intensity of it.
This pattern will have to do with the TDMA frame in terms of frequency.
So I think if it works for an external mic, where it’s easier for it to appear, it will also work with the internals.

I don’t know if you can observe the noise with an external microphone, but I think that’s the way to see it.
I don't think its certain that the noise is identical.

I agree it seems to be related to the TDMA but the problem does not seem to change for different power levels, which seems strange


BTW. I also received reports that the noise is caused by the dimming of the display, but I created a special version with no display light at all, and people still reported the noise. So I don't think it is related to the display.

Also, the RD5R has terrible voltage regulation, but does not have this problem, so it does not seem to be related to supp!y voltage fluctuations

do1jml
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Slight ticking sound

Post by do1jml » Sun Dec 20, 2020 3:11 pm

Other people noticed that there is a slight ticking sound on my transmissions. The ticking is relatively fast, several times a second. This happens when I am not moving (I know there is another problem when people are moving).

The sound happens on DMR and on analog FM.

Another GD-77, still on the manufacturer's firmware, does not have this ticking sound.

Any ideas?

kt4lh
Posts: 152
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Re: Slight ticking sound

Post by kt4lh » Sun Dec 20, 2020 7:15 pm

Is this when using an external hand mic or using the radio directly? If on a handmic, that's not new and you perhaps missed it before.

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