enter image description here

  • Location: Michigan, USA
  • Frequency: 7.074 MHz
  • Time: 1300 UTC
  • Vertical axis: 15 seconds per division

Most of this is FT8, and some JT65 can be seen as well. But buried in here is something else, labeled "A". It appears to be some kind of 8-FSK, possibly with the same 15 second interval as FT8.

Labeled "B" is a similar signal, though it appears to have a wider tone spacing.

What are these "A" and "B"?

  • $\begingroup$ Considering this would at least almost certainly not be a "single tone" FSK (there's multiple carriers active at the same time!), my guess would be that this is an OFDM signal – but it's really a guess, as I see none of the typical OFDM sync framing in that waterfall. $\endgroup$ Commented Feb 24, 2018 at 13:24
  • $\begingroup$ hm, maybe it's in here: sigidwiki.com/wiki/Category:Amateur_Radio $\endgroup$ Commented Feb 24, 2018 at 13:28
  • $\begingroup$ @MarcusMüller I'm not sure if more than one tone is active at a time or not -- the waterfall is very slow, so it's hard to say. $\endgroup$ Commented Feb 24, 2018 at 14:10

1 Answer 1


"A" appears to be T10, a mode available on the JTDX app. I believe "B" is simply an artifact from one of the over-driven FT8 signals on the band. No doubt I'll be corrected if I'm wrong :) 73 Dave - KB3MOW


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .