audio latency issue with gqrx resolved
Posted: Thu May 26, 2016 3:36 am
.... although i wish there were a more straightforward solution...
while trying to receive weather faxes using my SDRplay gqrx, and fldigi, i was having audio latency problems that would shift the sync randomly, resulting in a scrambled picture. however, recording the audio with gqrx's recording function creates a .wav file, that when played back into fldigi results in a good image...
i really don't like the idea of having to record hours of audio (especially in .wav format) to get a decent set of images from a fax session. if anybody else wants to try this, here's a condensed schedule of USCG fax transmissions in the US:
NMC Pt Reyes CA
freqs 4346, 8682, 12786, 17151.2, 22527 (offset -1.9khz)
times (Z) 0140-0420, 0655-1020, 1120-1240, 1400-1620, 1840-2230, 2320-0010
NMG New Orleans LA
freqs 4317.9, 8503.9, 12789.9, 17146.4 (offset -1.9khz)
times (Z) 0000-0300, 0600-0900, 1200-1500, 1800-2100
NMF Boston MA
freqs 4235, 6340.5, 9110, 12750 (offset -1.9khz)
times (Z) 0230-0510, 0745-1050, 1400-1615, 1720-2250
NOJ Kodiak AK
freqs 2054, 4298, 8459, 12412.5 (offset -1.9khz)
times (Z) 0340-0615, 0950-1215, 1540-1815, 2150-0030
for a document with more detailed schedules (as well as frequencies and schedules for every weather fax service in the world, download: http://www.nws.noaa.gov/os/marine/rfax.pdf
while trying to receive weather faxes using my SDRplay gqrx, and fldigi, i was having audio latency problems that would shift the sync randomly, resulting in a scrambled picture. however, recording the audio with gqrx's recording function creates a .wav file, that when played back into fldigi results in a good image...
i really don't like the idea of having to record hours of audio (especially in .wav format) to get a decent set of images from a fax session. if anybody else wants to try this, here's a condensed schedule of USCG fax transmissions in the US:
NMC Pt Reyes CA
freqs 4346, 8682, 12786, 17151.2, 22527 (offset -1.9khz)
times (Z) 0140-0420, 0655-1020, 1120-1240, 1400-1620, 1840-2230, 2320-0010
NMG New Orleans LA
freqs 4317.9, 8503.9, 12789.9, 17146.4 (offset -1.9khz)
times (Z) 0000-0300, 0600-0900, 1200-1500, 1800-2100
NMF Boston MA
freqs 4235, 6340.5, 9110, 12750 (offset -1.9khz)
times (Z) 0230-0510, 0745-1050, 1400-1615, 1720-2250
NOJ Kodiak AK
freqs 2054, 4298, 8459, 12412.5 (offset -1.9khz)
times (Z) 0340-0615, 0950-1215, 1540-1815, 2150-0030
for a document with more detailed schedules (as well as frequencies and schedules for every weather fax service in the world, download: http://www.nws.noaa.gov/os/marine/rfax.pdf