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Author Topic: UNID "Time Signal" at 7475 in AM mode  (Read 570 times)

Offline Strange Beacons

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UNID "Time Signal" at 7475 in AM mode
« on: December 16, 2019, 2034 UTC »
I was alerted to the presence of what sounds a bit like a time signal via a Reddit thread.

Anyone have any idea what this might be?

Offline KM0NAS

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Re: UNID "Time Signal" at 7475 in AM mode
« Reply #1 on: December 26, 2019, 1643 UTC »
It is interesting that it has a carrier which makes it distinct from the other 1 pps pip being discussed.

I made a recording on Christmas as it was present on the same freq. Today, the 26th it is still going strong.

This is the recording from the 25th.
https://www.youtube.com/watch?v=7muB-7GpjSk

~KM0NAS
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Offline KM0NAS

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Re: UNID "Time Signal" at 7475 in AM mode
« Reply #2 on: December 26, 2019, 1827 UTC »
I tried to do a TDoA for the signal and it took a lot of checking to find any kiwiSDRs that could pick it up! I tried 15 different ones around the country with no success until I tried Point Reyes CA. Nice strong signal there. From there I found other SDRs on the west coast that could pick it up.

I ended up using NA7U in Idaho, NAK in Washington State and AI6VN/KH6 in Hawaii. KPH came back with bad data so I left that out.

The results?



I tried again hoping to get good data from all stations. This time KPH worked but I got bad data from the Hawaii station and it was excluded. MUCH more interesting results though putting a nice hotspot right on the Fox Islands in the Aleutians.



The Fox Islands are uninhabited but the two islands within the forth most ring at the top are St. Paul and St. George islands, the Pribilof Islands. Both are inhabited. I am not aware of any current broadcast sites there. St. Paul used to be a LORAN site back in the day. Maybe someone is testing something new?

I wanted some signals from the West to add into the TDoA but I could not find the signal on anything in Japan.

Anyone else want to give it a go?

~KM0NAS
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Offline Strange Beacons

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Re: UNID "Time Signal" at 7475 in AM mode
« Reply #3 on: December 26, 2019, 1929 UTC »
Anyone else want to give it a go?

~KM0NAS

I tried multiple TDoAs but my results were all over the place, so I am not going to bother posting screenshots of my efforts. But, I really appreciate your help with this signal. It has had me puzzled for about a week now. I've been trading messages with a person on Reddit, who alerted me to the presence of the signal. Here is a link to the Reddit thread if you want to read what others have been speculating about it.
« Last Edit: December 26, 2019, 1942 UTC by Strange Beacons »

Offline Token

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Re: UNID "Time Signal" at 7475 in AM mode
« Reply #4 on: December 27, 2019, 1836 UTC »
There is another way to TDOA besides Kiwi, this signal might be a good candidate for that, but we would need 3 listeners addressing the signal.

The signal, on arrival at my location, is delayed from GPS T0 by ~6.6 msec.  Assuming (just as an experiment) the transmission is synchronized to the GPS second that puts it almost dead on the money 2000 km from me.  Or near this circle:



Of course, the timing my not be coincident with GPS T0, and then that circle means nothing.  But it does appear to be stable with / in sync with GPS.

T!
T!
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Offline KM0NAS

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Re: UNID "Time Signal" at 7475 in AM mode
« Reply #5 on: December 27, 2019, 1845 UTC »
Thanks for looking into this Token. I tried again this morning to do some TDoA and I found some stations with great signal. NOEMP, AI6VN and CM88cm seem to get it in strong but unfortunately they also pick up Radio Thailand which will screw up any TDoA attempts. Looks like the Udon Thani transmitter site used from 14:00 UTC to 20:15 UTC (at least according to online schedules)

For me in CST land that is 8:00 AM to 3:15 PM. I guess I will try in the afternoon with the Kiwi method. It would be interesting to get a few more circles like yours and see where they overlap.

~KM0NAS


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Offline refmo

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Re: UNID "Time Signal" at 7475 in AM mode
« Reply #6 on: December 27, 2019, 2339 UTC »
Three out of five TDoA's that I ran put it between Seattle and Vancouver (the other two put it in the middle of nowhere in central Washington state).  I didn't save a screenshot.
All the stations that I used for the TDoA were east/northeast of that location.
« Last Edit: December 27, 2019, 2342 UTC by refmo »
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Offline KM0NAS

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Re: UNID "Time Signal" at 7475 in AM mode
« Reply #7 on: December 28, 2019, 0005 UTC »
I tried again this late afternoon after the commercial station went off the air. I"m guessing my original images pointing to Alaska were thrown off by interference from the commercial station in Thailand. The SDR in Hawaii was unfortunately no longer getting a good signal and I could only find three really good signals to use. Unfortunately they were kind of lined up East-west. I would have liked to add in something further north or south.

When I first ran a number of TDoA samples and they all returned similar though not identical results. They were all a variation on something like this:



It shows the signal coming from either north or south of the middle of the western half of the US. Intriguingly these two lobes do head north and south toward the circle drawn by Token which I was thinking could narrow the location down to either somewhere near Baja or Edmonton (in general.)

I listened in to the VE6SLP SDR in Edmonton and sure enough the tics were coming in nicely. I added that to the TDoA and got a much more specific area.

I ran many scans and they tended to come back with either a vague area between Helena and Butte Montana but there were also some that came back pointing to Seattle including this very specific bullseye. The Seattle maps were FAR more specific and a much tighter bullseye which I would think indicated better data. (but I have not done a lot of TDoA). Montana seems to point more Military to me while Seattle in my mind point more to tech company. I was unable to use either of the online SDRs in the Seattle area for my analysis.




It also seems that depending on which stations you use you can end up with very different results for the TDoA. Quite interesting.

I tried to do more but at 11:45 UTC a commercial station came on the frequency and I started to get interference and figured the data would no longer be good so I quite for the night.

~KM0NAS
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Offline KM0NAS

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Re: UNID "Time Signal" at 7475 in AM mode
« Reply #8 on: December 28, 2019, 2018 UTC »
With some locations coming back as Victoria Island as well I wonder if it isn't something at Esquimalt Marine Forces Headquarters.

48.429556, -123.429149

https://www.google.com/maps/place/48°25'46.4%22N+123°25'44.9%22W/@48.429556,-123.431343,945m/data=!3m2!1e3!4b1!4m5!3m4!1s0x0:0x0!8m2!3d48.429556!4d-123.429149

There are a number of antenna towers there.

~KM0NAS
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Offline tiNG

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Re: UNID "Time Signal" at 7475 in AM mode
« Reply #9 on: December 29, 2019, 0811 UTC »
Probably coming from this TX site

49.110079, -122.245270
73 & 55
Thomas
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Offline Token

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Re: UNID "Time Signal" at 7475 in AM mode
« Reply #10 on: December 29, 2019, 1714 UTC »
It also seems that depending on which stations you use you can end up with very different results for the TDoA. Quite interesting.

This kind of results can sometimes be an indicator that there is more than one synchronized transmission on a given frequency.  In fact, multiple sync'ed transmission sources is one way to intentionally spoof TDOA.  I have seen it used in various military applications.

Not saying that is what is causing your results, I don't know, but it is something to keep in mind.

T!
T!
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Offline KM0NAS

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Re: UNID "Time Signal" at 7475 in AM mode
« Reply #11 on: January 03, 2020, 1638 UTC »
After being off the air for a few days, the signal sprang back up today still on 7475.

I did notice that if you look up three posts I have a TDoA map with the tightest bullseye I have yet created for this source. It was on December 28th. What I hadn't realized before is that the bullseye is very close to on top of NLK, the Jim Creek Naval Radio Station.

The VLF antenna there is likely not the source of this but perhaps they are experimenting with something new.

~KM0NAS
« Last Edit: January 03, 2020, 1722 UTC by KM0NAS »
*KM0NAS*
Kenwood TS-570D
Soft66RTL2
40 meter dipole @ 40' height
20 meter dipole @ 40' height
10 meter vertical @ 16' height
Beacon MN on 13562.8