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librtlsdr
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attempt at calibration of Rx level and No

development
David Rowe 2020-11-23 09:13:03 +10:30
parent 92ff2a9e8c
commit 7398187ba9
1 changed files with 25 additions and 6 deletions
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31
src/rtl_fsk.c
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@ -113,6 +113,8 @@ static int periodic_output = 0;
static uint8_t filter = 0;
static int inject_snr = 0;
static int log_snr = 0;
static float RxGain = 0.0;
static int Rs = DEFAULT_SYMBOL_RATE;
void usage(void)
{
@ -390,16 +392,21 @@ static void rtlsdr_callback(unsigned char *buf, uint32_t len, void *ctx)
}
/* optional SNR info to stderr for logging */
if (log_snr && (rx_status & FREEDV_RX_BITS)) {
float S,N;
float S,N,RxleveldBm, NodBmHz;
freedv_get_fsk_S_and_N(freedv, &S, &N);
RxleveldBm = 10*log10(S) + RxGain;
NodBmHz = 10*log10(N) + RxGain - 10*log10((float)Rs);;
fprintf(stderr, "%lu ", (unsigned long)time(NULL));
fprintf(stderr, "Rx Frame Sloc: %8.4f Nloc: %8.4f snrloc: %2.2f ", S, N, 10*log10(S/N));
fprintf(stderr, "Rx Frame Rxloc: %6.2f Noloc: %6.2f snrloc: %5.2f ", RxleveldBm, NodBmHz, 10*log10(S/N));
memcpy(&S, &bytes_out[2], sizeof(float));
memcpy(&N, &bytes_out[6], sizeof(float));
if ((S>0) && (N>0))
fprintf(stderr, "Srem: %8.4f Nrem: %8.4f snrrem: %2.2f\n", S, N, 10*log10(S/N));
if ((S>0) && (N>0)) {
RxleveldBm = 10*log10(S) + RxGain;
NodBmHz = 10*log10(N) + RxGain - 10*log10((float)Rs);;
fprintf(stderr, "Rxrem: %6.2f Norem: %6.2f snrrem: %5.2f\n", RxleveldBm, NodBmHz, 10*log10(S/N));
}
else
fprintf(stderr, "Srem: %8.4f Nrem: %8.4f snrrem: %2.2f\n", 0., 0., 0.);
fprintf(stderr, "Srem: %6.2f Nrem: %6.2f snrrem: %5.2f\n", 0., 0., 0.);
}
}
@ -466,7 +473,6 @@ int main(int argc, char **argv)
int dev_given = 0;
char hostname[256];
uint32_t frequency = 100000000;
int Rs = DEFAULT_SYMBOL_RATE;
int M = DEFAULT_M;
int channel_width = DEFAULT_CHANNEL_WIDTH;
uint32_t bandwidth = DEFAULT_BANDWIDTH;
@ -530,6 +536,19 @@ int main(int argc, char **argv)
break;
case 'g':
gain = (int)(atof(optarg) * 10); /* tenths of a dB */
/* note YMMV - these will vary across RTLSDR brands and samples */
if (gain/10 == 49)
RxGain = -90.7;
else if (gain/10 == 45)
RxGain = -85.6;
else if (gain/10 == 40)
RxGain = -81.1;
else if (gain/10 == 35)
RxGain = -76.9;
else if (gain/10 == 30)
RxGain = -71.0;
else
fprintf(stderr,"rtl_fsk: WARNING RxLevel not calibrated at this -g gain\n");
break;
case 's':
samp_rate = (uint32_t)atofs(optarg);