7478KHz & 7486.5KHz 'rhythmic grinder' sounds usually in pairs?

[VE3PMK]

For the last several weeks almost every night just a few seconds after 23:01 eastern time a signal appears on 7478KHz USB and on 7486.5KHz USB. They almost always appear in pairs but occasionally only one will appear. They differ in cadence but sound very similar and I receive them S9 to S9+20 at times from a rural site on the north shore of Lake Erie but also receive them here in London Ontario as well as on a few web SDR receivers in Europe. Has me baffled, they're not like anything I've heard before and if any experienced utility listeners could have a listen I'd sincerely appreciate any help identifying them.

73, Pat
ve3pmk

 

[Token]

If they appear at a regular time each day, and you do not recognize it as FAX or RTTY (assuming you are familiar with those sounds), my first thought is it is a jammer, hitting a specific SW broadcast that starts every day at that time. The Cubans have a grinding jammer.

I will give a listen tonight, and see if I can hear it.

T!

 

[VE3PMK]

I don't think it's a jammer

I've been an SWL since the mid 70's and a licensed ham since 1987. It's not RTTY, nor fax, nor any other digital mode I'm aware of, but it has structure and on a waterfall you can see it's probably data. Tried getting a DF on it but my TGM MQ26 has no real directionality below 20m. When I did a 360 with the beam there was no noticeable null nor peak. Longer wire antennas get it best but the general coverage vertical picks it up okay as well. Up here in Ontario Canada, before they went to APCO25 the OPP used an analog audio mode that had a similar (but not the same) type of repetitive grinding data sound whenever the channel was idle. This sounds pretty close to what that did. The 7486.5KHz always has a faster cycle than the 7478. I've looked for other freqs (especially when only one appears) but have yet to discover any frequency but the two I know of.

Again, if anyone can lend an ear (and possibly a general QTH with a beam heading) we could get closer to identifying the likely source.

73,
Pat

 

[Token]

I was able to hear it tonight, in fact it is on right now (0544 UTC) on both frequencies. It is the Cuban jammer I mentioned. This jammer is well known for throwing spurs on unoccupied frequencies, while it hits its intended target on other freqs. Also, the bearing (using SteppIR DB36) is correct to be Cuba, 101 degrees true from my location in the Mojave Desert of California.

T!

 

[VE3PMK]

I agree it's very similar.

They're jamming Marti on 6030 and 7365 right now. I tried mixing 7478 & 7486.5 and did a compare to 7365 as well as 6030 and neither of the Marti freqs have the same cadence, but they are certainly similar sounds. 6030 seems to be a mix of a bubble jammer as well as some sort of quacking/squaking jammer but still not in sync with either of the other freqs. 7365 also has a jammer on it right now (04:17 UTC, 2014 Dec 13) but again the cyclic rate does not match any mix I can create in the shack. (I'm using four parallel receivers into a mixer.) I will agree they are very similar and it probably is a yet another jammer of some description. It would be interesting to know what signal the 7478/74686.5 units (or it's spurs) are targeting.

Thanks for having a listen and posing the replies. If you ever spot a freq that matches the cadence of the freqs in question please share, I'll do the same.

Thanks again,
Pat, VE3PMK

 

[VE3PMK]

Albeit it similar, I'm thinking this is not a jammer.

I've looked into this a bit deeper and I think it's a sked of ALE data. It fired up one evening last week and a few minutes into it it stopped, briefly sounded like encrypted voice for about 15 seconds, and then went back to the cyclical data grind. Also, watching propagation patterns it does not always rise and fade with other signals known to be originating from the Caribbean. In any event, it's origin is not likely going to be identified with absolute certainty anytime soon.

Hope Santa is extra generous to the radio reference crowd out there and all the best in 2015!
73, Pat