I have a code that sends a beacon every 1 minute with a data-rate of 1200bps (BPSK-G3RUH). I do receive the signal using a custom software defined ground station that also decodes the beacon. After a couple of minutes (10 - 30 minutes), my software defined ground station stops receiving the signal. Thus I used Airspy SDR to have a visual on the signal. This is the signal I see when I perfectly receive the signal. This is the signal I see after a few minutes.
The perfect signal has a higher peak and a longer duration.
My question is, what caused the signal to change like this? Could it possibly be a hardware problem from the transceivers or the antenna?