I'm playing around with an SDRPlay. I'm using the CubicSDR app, and I'm tuning around the HF bands. I get to 5.650 MHz and I see this:
This looks like a bunch of discrete RTTY signals. How would I go about identifying and decoding some of these signals?
Things I tried:
- I looked through the Globaltuners Frequency Database. 5600 kHz appears to be an aeronautical band:
According to this site:
MWARA is the term for Major World Air Route Areas, which support HF Radio communications to aircraft outside of VHF range.
I looked around for aeronautical data formats, and found HFDL, however these signals look and sound nothing like that format.
I opened up the Signal Identification Wiki and looked for signals that appeared to have the same frequency spectrum. Each of these signals seems to have a clear signal of two tones, which confirmed my suspicions that it might be RTTY.
I ran fldigi in RTTY mode and tried to decode one of the signals, but it didn't produce anything intelligible. But I may be in the wrong mode, or this is a proprietary protocol, or ... ?
How can I systematically what this signal might be? For example step 1 is it FSK? Step 2 how many tones does it use? Step 3 what is the frequency separation? Step 4 what known protocols have these parameters?
Are there any software packages that can do this?