Hi,
I use HC-12 radio modules for project, and they work well, however the latest batch I bought, has problems.

I use terminals screens to see what's being tranmitted, also a hand held radio, I can hear both TX and RX on the correct frequency.
2x good modules send/receive ok, but even though I can hear the 'NOT WORKING one, it doesn't actually transmit properly.

I used a PC SDR to see the signal of both modules, but the NW one shows lots of leakage each side of the frequency, which isn't centred on the correct frequency.

Here are images of both, in case anyone has had the same trouble.
C

 

hi C,
Is this shiny face actual copper ground plane.??
If so the soldering could be a problem.

E

 

hi C,
Is this shiny face actual copper ground plane.??
If so the soldering could be a problem.

E

Morning E,
No it's just a coating.
I'm no expert, but to me it seems the signal output, doesn't have the correct filtering.
C