One of my "go to" frequencies for testing my HF equipment is 6338.6KHz USB. There I will usually find the US Coast Guard's WeFAX service pushing out weather information in FAX format. This is time tested way to send weather maps and printed statements to ships at sea. And yes, FAX machines are still a thing.
My local WeFAX transmitter (callsign NMF) is up in Boston and so presents an approximate 300 mile distance between me and the transmitter. This would be about the same if I were a ship at sea.
NMF transmits on a handful of frequencies depending upon the radio conditions and the time of day. Today I decided to try their 12750KHz frequency (a first for me) to see if it would yield better pictures than I have been able to receive lately. With the rise in solar activity and the local electrical noise around here 6338.6KHz (dial) has been a tough catch.
As if by magic I am receiving an interference free (if a little blurry) FAX message. As the day goes by one can receive all sorts of written weather statements and pictures. They even send out satellite pictures too. A schedule of all the world wide FAX transmissions can be found here.
I am using my FT-710 HF transceiver and the FLDigi software. But "hold on" I hear you say. "The radio is tuned 1.9KHz lower than the frequency published by the USCG". Why yes it is. It's a USB signal with its tone pair centered on 800hz. In order to receive both the mark and space tones (it is data after all) one has to tune down in frequency so that the tones fit into the pass band of the radio. The accepted tuning offset is 1.9KHz giving a tone pair frequency of 1500/2300hz.
FLDigi software |
FT-710 receiver |
Follow this link for an explanation of how to receive these pictures. It's pretty easy.