I am working with ADF7021-N with an STM32 microcontroller. I am measuring the BER which is fine when transmitter and receiver are close to each other. But when they are further, like 90 meters, and the attenuation fo the signal is higher (signal power is arround -75dBm at the peak) i start having strange behavior. At that range, when i receive a packet BER is 0, but the problem is that there is packet loss packets (100 packets out of 1000, so 10%). I think it is a problem with the CDR at the receiver, so it is not able to synchronize early enough to detect SWD.
I use 869.5MHz as central frequency with a 19.68MHz crystal, RC2FSK with alpha=0.7, fdev=3kHz, 9.6kbps, preamble of 128 bits, SWD=0x123456 with 0 errors allowed.
My question is if it is normal to los packets in this scenario and, if not, which could be the source of this problem and its solution?
Thank you very much.