Slight ticking sound

[VK3KYY]

The same people who have been testing these changes to the screen and keypad have previously tested with and without backlight and it makes no difference to their radios.

They have also tested GPIO (On / Off only) control of the backlight, rather than the PWM / adjustable brightness version

Again, this made now difference to them.

Adjusting the power level to the bare minimum i.e below 50mW also made no noticeable difference to all the people who tested.

So whatever is causing this problem on some radios is fairly fundamental

All we have is an increasing long list of things which don't seem to affect the problem.

[VK3KYY]

BTW.

The ticking sound is not the only problem.

I know one other user where their audio sounds like they have a fan in the shack blowing air.

Also, I have multiple reports on the DM-1801 of tones on both Rx and Tx audio.
I know one of the tones is reported to be 1750Hz, but I can't remember what the other tone frequency is.

These may be unrelated to the ticking noise, its difficult to know

[VK3KYY]

I've now also tried running the firmware as DMR Tier1, and people tell me that the problem is still noticable.

I'll need to double check that using Tier1 is definitely not turning the Tx on and off during transmission, but audibly it seems to be generating a continuous signal.

This makes the problem very strange, as it may not be caused by supply voltage fluctuations, and is perhaps something do to with when the C6000 is accessed via SPI, which perhaps generates some internal noise that is being picked up by the ADC in the C6000

[YL3IM]

Got two Radioddity GD-77 radios which have been immediately flashed to OpenGD77. For one of them there's the same effect: the chopping sound. Unfortunately, I cannot tell whether the same issue persists on the stock firmware.

[VK3KYY]

This thread is now a duplicate of another similar thread about a ticking noise.

So I have merged these 2 topics

[YL3IM]

Modify a speaker microphone to keep out DMR pulsed RF feedback.

(Credit to Owen Duffy VK1OD for this)

If you have a speaker microphone that you like, but is affected by RF feedback from DMR’s pulsed RF getting back into it, causing your transmitted audio to become distorted, you can perform modifications to reduce or even eliminate this problem. I have carried out the modifications, adding a SMD capacitor across the speaker microphone electret element, and adding a SMD inductor in line with the positive line of the electret element, and confirm it works very well indeed. See Owen’s mods at: http://owenduffy.net/blog/?p=9326

Found it via http://members.optuszoo.com.au/jason.re ... 77mods.htm

Can someone tell what exactly should be altered on the station itself? With pictures :)

[VK3KYY]

I may have a fix for the ticking sound

https://drive.google.com/drive/folders/ ... sp=sharing


Note.

This version is experimental, and it may completely stop the DMR Tx audio working. However, I've had reports from 2 people that this fix definitely worked on their GD-77

[YL3IM]

Thank you very much!

Just tried it out: the "motorboat" pulsing sound has disappeared — at least when I say nothing and keep silence while pressing PTT
However the talking pitch is not linear, it goes with some stuttering. Tested it out with a parrot.

[VK3KYY]

Try this version

https://drive.google.com/drive/folders/ ... sp=sharing

[YL3IM]

Thank you! The second one 1e28b83 sounds better than ad178df on my GD-77.