OpenGD77

Guys

I've noticed when doing some testing, that on FM I get quite a lot of mains hum on FM Tx.

The primary cause of this seems to be the mains charger unit, but also things are worse if I use a speaker mic.

Strangely, things also seem worse on 2m than 70cm, but that doesn't make any sense.

I tried various power levels, but I get the problem even at 250mW.

This is not going to be an OpenGD77 firmware problem, but I think that anyone running their radio in a charger all the time, like I do, may have degraded Tx performance both on FM and DMR because of the hum (though in theory it should not matter to the 4FSK FM signals that DMR uses)

I had the same with mainly cheap chinese mics.
If I use Kennwood mics I newer had that problem.
At some points also DMR was affected.

VK3KYY wrote: ↑

Tue Jan 21, 2020 7:01 am

...
I've noticed when doing some testing, that on FM I get quite a lot of mains hum on FM Tx.
...

It is a known problem, at least for me. Handheld transceivers usually have cheap chargers and hum is expected, if used while charging. I was always told by "older" amateur radio operators not to use it that way, for mentioned reason. I wouldn't worry about it.

BTW, there's a mod to reduce RF noise, but you probably know that.
Modifications, hints, tips and technical information for the Radioddity GD-77

The TP5100 charger drop-in also is said to improve the RFI on the charger, although it's still pretty significant. Weaker repeaters on one HT disappear as soon as I drop the GD77 or MD380 into the charger, so for me it's not so much "through" the charger as RFI from the charger.

I believe the original charger was worse, but if you're curious I can dig it out, I only modified one of the two.