That’s not the correct syntax.
This is:
RECEIVER_OPTIONS="--sdr driver=rtlsdr,serial=00003000 --sdr-gain 49 --format CS8"
This for AGC:
RECEIVER_OPTIONS="--sdr driver=rtlsdr,serial=00003000 --sdr-auto-gain --format CS8"
That’s not the correct syntax.
This is:
RECEIVER_OPTIONS="--sdr driver=rtlsdr,serial=00003000 --sdr-gain 49 --format CS8"
This for AGC:
RECEIVER_OPTIONS="--sdr driver=rtlsdr,serial=00003000 --sdr-auto-gain --format CS8"