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Utility Listening - Discussions regarding monitoring government, military, aircraft, ship, and other misc communications in the HF/MW/LF bands.

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Old 01-02-2018, 9:43 PM
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Default Unknown pips / pulses in the ham 40 meter band, 01 Jan, 2018, 2238 UTC

01 Jan, 2018, about 2238 UTC, Tom S in the HFU Ryver chat commented on hearing an odd set of pulses or dits on multiple frequencies in the 40 meter ham band. I looked and sure enough, there were 4 frequencies with short duration dits on them, and a pretty strong signal is was. Eventually using remotes and talking to other listeners in chat this signal was heard from the US west coast and Pacific North West to Eastern Europe.

Each frequency was pulsed once per second. Each pulse or dit was about 20 millisecond long. The initial set of frequencies was 7035 kHz, 7040 kHz, 7065 kHz, and 7105 kHz.

Looking closer showed that the pulses on all 4 frequencies were not transmitted simultaneously, rather the pulses were sequencing or cycling through the 4 frequencies. Frequency 1, then freq 2, then freq 3, then freq 4, and back to freq 1 to start the cycle over. Each 20 msec pulse was followed by 20 msec of dead air before the next frequency in the set transmitted.

In the first set noted, active from 2238z until 2250z, the sequence was 7065 kHz, 7040 kHz, 7035 kHz, and 7105 kHz, in that order. Back to 7065 kHz to start the cycle again.

This picture shows the timing relationship between 7065 and 7040 kHz in that first set.
https://a4.pbase.com/o10/50/78250/1/...40_vs_7065.jpg

At 2250 UTC the frequency set changed, and now the sequence was 7066 kHz, 7040 kHz, 7000 kHz, and 7070 kHz.

At 2323z the signal went off air for a minute, and came back on at 2324 UTC, now with the sequence of 7065 kHz, 7040 kHz, 7105 kHz, and 7000 kHz. This set continued until 2355 UTC.

At 0005 UTC, now 02 January, the signal came back with the sequence 7065 kHz, 7040 kHz, 7105 kHz, and 7120 kHz. At 0016 UTC this frequency set changed to 7065 kHz, 7040 kHz, 7010 kHz, and 7105 kHz.

The signal went off air at 0019 UTC and was not seen again.

Note that in the 5 sets of frequencies observed 7065 and 7040 kHz were always the first two used, the last two frequencies changed with each set.

Both while the signal was active and for several hours after it ended I attempted to find it on other freqs, I did not see any active.

These pulses were 1 pulse per second per frequency and the timing appeared very stable over the hour and a half observed. The lead pulse, always 7065 kHz, always arrived at my location about 9.6 msec after UTC time zero. Although there is really nothing to indicate it (and nothing to NOT indicate it), if we assume the lead pulse is made on the start of the UTC second then we can plot, based on propagation time, the range from my location. This results in a range ring looking something like this:

https://a4.pbase.com/o10/50/78250/1/...dits_delay.jpg

Pure speculation, and nothing to prove it either way. But interesting how the circle goes right near WLO's location in Mobile, AL, as well as near a few other known radio sources near the Great Lakes.

Anyway, I have no idea what this signal was / is used for, and it might be just some kind of test signal. But I found it interesting and it was, in my opinion, well over ham power levels. I will be keeping my eyes open for it.

I made a video of the signal and put it up on my YouTube channel. The video is boring with lots of text added carrying the details. There are sections of the video for each of the 5 sets of frequencies seen and audio comparing the timing of each frequency set. So not something to keep the average YouTuber engaged, but maybe someone interested in shortwave oddities might find it revealing.

https://www.youtube.com/watch?v=mSP8pHtqOd4&

T!
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Old 01-02-2018, 9:57 PM
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Hey T. I listened to your video and I heard what I think was a distinct skip in pips of one pip, at the 16th in the vid, much like WWV has at the 29 second mark. What do you make of that? Not to mention the pips have the same exact sound as WWV pips like someone's hitting a piece of wood.
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Old 01-02-2018, 10:02 PM
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Originally Posted by ridgescan View Post
Hey T. I listened to your video and I heard what I think was a distinct skip in pips of one pip, much like WWV has at the 29 second mark. What do you make of that?
I noted that also, several times in the hour and a half+ it skipped a pulse. However, it was not consistent or if it was other signals covered up that fact

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Old 01-02-2018, 11:12 PM
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Interesting,

Coming from an avionics background the first thing that I notice is that the center point of the circle you provide is centered a bit northwest of KXTA, give or take a couple of minutes but still close to KXTA.

In fact if I expand a waypoint on my Garmin G3X navigator which is centered on KXTA and expand the circle out I get a circle that's very close to yours.

BTW, KXTA is an avionics callsign located somewhere out in the Nevada wilds at ~4400 feet elevation.
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Old 01-03-2018, 8:56 AM
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Originally Posted by mm View Post
Coming from an avionics background the first thing that I notice is that the center point of the circle you provide is centered a bit northwest of KXTA, give or take a couple of minutes but still close to KXTA.

In fact if I expand a waypoint on my Garmin G3X navigator which is centered on KXTA and expand the circle out I get a circle that's very close to yours.

BTW, KXTA is an avionics callsign located somewhere out in the Nevada wilds at ~4400 feet elevation.
No, the center point of that circle is my house, in the Mojave Desert in California, well over 100 miles to the south west of KXTA. I hope you are not saying my house is at Area 51....although that might explain a few things....

The center point of the circle does not represent the source of the transmissions, but rather the circle itself represents a possible range from my location to the source. In other words, the source might be someplace near the line of the circle.

The apparent leading pulse of the 4 transmitted pulses, I mean the first one in time, arrived at my location a fairly consistent 9.6 milliseconds after the UTC second. If (and it is only an if) the set of pulses is synchronized with UTC time (very possible if they are using GPS time or GPS 1 PPS to trigger) then that would indicate the propagation time from the source to my location is about 9.6 msec.

That green circle on the map is the rough distance, range, from my location that the source would have to be to have a propagation time of about 9.6 msec. That circle is approximated using single hop propagation and an ionospheric altitude of about 250 km, so a rough guess. But if the source does indeed send the first pulse on the UTC second it should be fairly close to that line. If the source triggers in sync with, but shortly after the UTC second, also possible, the source would be someplace inside that circle.

Of course, it is also possible that the source triggers on some other 1 pulse per second source, unrelated to GPS or UTC time, in which case the arrival time at my location means absolutely nothing. But hey, it is a fun thought exercise. Lots of people like to use GPS time as an easy sync source, so I think it is a fair possibility.

T!
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