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Strange Digital Telemetry on 1944.5 anyone else?




 
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Author Topic: Strange Digital Telemetry on 1944.5 anyone else?  (Read 5139 times)
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KB1VWC
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« on: March 14, 2023, 07:58:22 AM »

   I am receiving a strange Digital telemetry signal both day and night on 1944.5. This started about 3-4 months ago and I assumed it was just something strange and local to my QTH. This started the usual unplugging everything and using a battery powered receiver, but the signal still persisted.  Trying to use a loop antenna proves quite difficult as the signal is very quick and intermittent. Typically about 10-20 over nine signal. This is really messing up both the grey-haired net and the AWA sideband net. I can use Sync upper sideband for am detection, but many times QRM is preventing this.

  Last Night on the AWA net, Joe W3GMS also mentioned and played this exact noise/interference at his QTH. My question is how many others can hear this noise and does anyone else know what this is?  I am guessing some form of maratime bouy giving my location close to the south coast of Cape Cod. I think trying to TDOA or triangulate this thing would be difficult.  Attached are wave files and a screen shot taken around 7:40AM DST. It's definitely louder and more annoying at night.

   Thanks

  Steve   
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* 1944_5data.JPG (89.44 KB, 491x629 - viewed 80 times.)
* kb1vwc.ddns.net_2023-03-14T11_37_53Z_1945.00_lsn.wav (576.04 KB - downloaded 78 times.)
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« Reply #1 on: March 14, 2023, 10:48:49 AM »

What I heard on 160 and on 75 to some degree was that like a wooden ship 'groaning'. It would come and go like a wave. If I hear it again I will try to make an recording with my cell phone.
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w9jsw
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« Reply #2 on: March 15, 2023, 02:37:55 PM »

I see it here in So. Illinois. Around S5-7. So I don't think it is maritime related in just your east coast area. I thought it was a spur from my switching PS. Observed at 1:30pm CDT.

John


* Capture.JPG (68.43 KB, 554x538 - viewed 60 times.)
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N1BCG
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« Reply #3 on: March 15, 2023, 02:38:11 PM »

Steve, your Kiwi receiver was the only one of over two dozen I tried that had any meaningful reception of the signal last night. Coastal and inland U.S., Canada, and Europe were included so TDoA won't be practical unless the signal level increases. It took a lot of filtering to hear it on an analog receiver is SW Connecticut. A 1 Watt transmission matched the strength and frequency on 1944.40 kHz although there was QSB while the mystery signal had none.

The fact that you can hear it 24/7 is meaningful. Perhaps it's coming from Martha's Vineyard or Nantucket. I'll take a listen the next time I'm out that way.
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N1BCG
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« Reply #4 on: March 15, 2023, 02:39:56 PM »

I see it here in So. Illinois. Around S5-7.

Wow!  I'll try some Kiwis in that area. Interesting, thanks!
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w9jsw
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« Reply #5 on: March 15, 2023, 02:43:43 PM »

Just added a pic. Maybe it is a balloon that has lost it's way?  Roll Eyes

Can't see it on the N1NTE kiwi I usually use...
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N1BCG
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« Reply #6 on: March 15, 2023, 02:59:49 PM »

Well, that's just the darndest. These four receivers pick it up well although I'm not sure it's the same signal. The bursts sound more intermittent on the first receiver on average than on the rest:

http://kb1vwc.ddns.net:8073/?f=1944.40cwz12   East Falmouth MA

http://207.135.223.250:8073/?f=1944.40cwz12   Edinburgh, IN

http://boomerthedog.com:8073/?f=1944.40cwz12   Pittsburgh, PA

http://96.228.44.53:8073/?f=1944.40cwz12   Richmond, VA

I also couldn't find any mention of it on HF Underground and they're always listening.
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w9jsw
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« Reply #7 on: March 15, 2023, 03:18:10 PM »

May be an invalid data point but I can't see it on my 80/40/20 fan dipole that has S6 noise. I can see it on my S1 noise beverage that is pointing east and I can see it on the 160M inverted L that also has S6 noise.

Interesting.

On edit - I can see it on the horizontal dipole now. Must have been lost in the noise.
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KB1VWC
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« Reply #8 on: March 15, 2023, 10:27:12 PM »

Glad Iím not too crazy.  Itís really interesting that you can receive it John on an inverted l but not on a horizontal antenna. Iím also using an inverted L with the Kiwi here on the Cape. Clark had suggested Russian Submarine..At this point who knows. Itís just an odd signal..not sure if itís some form of narrow bursted FSK?  Definitely not cw. Always great to start the mystery wheels turning..

Steve
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Tom WA3KLR
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« Reply #9 on: March 16, 2023, 07:56:11 PM »

I repaired my 160-meter end-fed antenna downlead later this afternoon and I have listened several times on 1945 kHz LSB starting just before 5 p.m. Eastern time.  The signal is a constant FSK just barely audible.

Now at 7:50 p.m. the signal is barely stronger; about 1/2 S-unit above the QRN level.  I will listen again later this evening.

My QTH is 11 miles south of Allentown PA.
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w9jsw
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« Reply #10 on: March 17, 2023, 07:57:20 AM »

I glanced at fundamentals in the BC band that could render this as a harmonic. Nothing found. The second harmonic of 972.25 kc is 1944.5 kc. Third harmonic of 648.16kc is 1944.5kc.

Was thinking that a BC station could be generating some harmonics. A long shot given that the signal looks digital.
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Tom WA3KLR
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« Reply #11 on: March 17, 2023, 10:20:19 AM »

I listened again at 11 p.m. last night  - same signal level, just a little above the QRN level.

I listened at 8:30 a.m. this morning - the signal was detectable but very weak. These signals are FSK so is not a BC carrier harmonic, at least what I am hearing.

It appears to me that the signal level is not changing much day to night, so I think the transmitter location is not too far away since dramatic propagation change over 24 hours is not seen.

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73 de Tom WA3KLR  AMI # 77   Amplitude Modulation - a force Now and for the Future!
KB1VWC
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« Reply #12 on: March 17, 2023, 10:16:36 PM »

Same signal is also on 2.000Mhz..Sounds completely identical here on the cape to the 1944.5 signal. I havenít tried day night comparisons on the second one yet.

Steve
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w9jsw
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« Reply #13 on: March 18, 2023, 09:40:54 AM »

https://www.hfunderground.com/board/index.php/topic,90804.0.html

Others see it as well...
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w9jsw
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« Reply #14 on: March 18, 2023, 09:58:14 AM »

I spent some time a few minutes ago looking at both signals on Thetis. I can view both in real time. They are similar but not identical. i.e., both appear to be the same type of signal, but they are not the same signal. The amplitude of the 1944.5 signal varies more than the 2000 one and the pulsing of the digital signal on the waterfall appears to be different.

It is interesting to note that I can see the signal clearly on the 160M inverted L at 8:45am cdt. The background is around S4. The signal is peaking at S7. A very clear signal on a band that is usually dead at this time of day.



* Screenshot 2023-03-18 085742.jpg (43.56 KB, 357x607 - viewed 64 times.)

* Screenshot 2023-03-18 085924.jpg (36.98 KB, 317x565 - viewed 65 times.)
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w9jsw
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« Reply #15 on: March 18, 2023, 12:17:50 PM »

I am seeing similar but fainter signals on 1969.7 and 1974.750.

I have a short video of all 4 signals that I can share by email. It won't let me upload a mp4 type of file.
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N1BCG
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« Reply #16 on: March 18, 2023, 09:24:29 PM »

Some more frequencies with similar signals that seem to appear 24/7 on multiple receivers:

1959.60, 1969.60, 2000.00
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KB1VWC
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« Reply #17 on: March 19, 2023, 03:16:34 PM »

OK, More data points and I'm going to start the assumptions here.   I have signals at all of those frequencies stated.   Maybe even a few above and below.   When the data bursts occur, they fill the spectrum between 1920 and 2300Khz. Seems to be two main "carriers" which I'll agree with John, while very similar are not identical. Both carriers however data burst at the same point in time.

   Now for assumptions..

 Has to be vertically polarized with a very good ground system. There is no way at 2:30PM EDT I can receive this signal at -60DBM and John out in IL should also receive this signal if it was horizontally polarized.  Daytime D-Layer absorption should take it out.

Second assumption.

 It's running some serious power bursts.



  Shot taken at 2:33EDT local 18:33UTC

   Note the bright wideband data in the middle of the screen between 1920 and 2300.. There is noise in here as well.  Inverted L daytime in an urban environment. I figure an S6 noise floor is pretty good.


Steve  KB1VWC


* 160 noise.JPG (185.21 KB, 1580x291 - viewed 60 times.)
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N1BCG
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« Reply #18 on: March 19, 2023, 04:16:35 PM »

I'm thinking a lot, if not all, of this is QRM from any number of electronic devices. Granted, similar signals appear on the same frequency on several receivers, but I'm starting to believe that they are a result of a combination of oscillators in computers connected to the SDRs.

The argument against an external signal is that these seem to be immune to any propagation effects. That's a tough clue to ignore given that they are heard well on some receivers but not on most, even ones with decent 160M reception.

For example, there's a steady carrier on 3862.40 that is present at the same signal strength 24/7 in East Falmouth, MA:

http://kb1vwc.ddns.net:8073/?f=3862.40cwz12

However, none of a dozen other receivers in the region can pick it up. As an experiment, I sent a 1W signal that could be heard clearly on 3862.50 (S5) as well as on a receiver in Holland, MA (S7) yet the 3862.40 signal is non-existent there:

http://sigmasdr.ddns.net:8076/?f=3862.40cwz12

I'd prefer it were a Russian sub or Chinese spy balloon near Menauhant Beach, but it's not looking good.
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KB1VWC
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« Reply #19 on: March 19, 2023, 05:58:51 PM »

"I'm thinking a lot, if not all, of this is QRM from any number of electronic devices. Granted, similar signals appear on the same frequency on several receivers, but I'm starting to believe that they are a result of a combination of oscillators in computers connected to the SDRs."

  I have to respectfully disagree Clark. I shut everything down in this house back in December and used a Grundig Satelite amateur on batteries..Easy copy. Two days ago I took a Channel Master 6514 8 transistor battery portable portable down to the beach, and I can copy 1944.5 when there is AM on 1945 there to decode the burst..Do to the sophisticated nature of the channel master, copy wasn't as easy.  No microprocessors anywhere to be found.  Cannot argue with the steady carriers here there and everywhere..Between my own solar array and every other digital toy, MF an HF ham radio is now the modern day version of wack a mole.

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N1BCG
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« Reply #20 on: March 19, 2023, 08:52:08 PM »

You mentioned that on the air and I certainly don't doubt your findings. What complicates matters is that some of these signals seem to have only their frequencies in common, and even then, the signals differ geographically. I have yet to find even two SDRs that can hear the same signal which makes a TDoA scan impossible. This is a new experience to me.

A half dozen receivers in New England were able to receive a low power test signal, as was yours, but only yours was receiving the anomalies. Perhaps it's something of very low power being carried along power lines. I've tracked low frequency signals that go for miles along a road with overhead lines yet cannot be heard 1/4 of a mile away from those lines.

It would be great to figure these out but my guess is that it will take some out of the box thinking.
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w9jsw
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« Reply #21 on: March 20, 2023, 12:33:48 PM »

This chart - https://ntia.gov/sites/default/files/publications/january_2016_spectrum_wall_chart_0.pdf

shows radiolocation as a primary use of the frequency between 1900-2000kc. Searching on radiolocation finds this older article. I cannot find a date on this but suspect it is 1980/90s vintage. Talks about Loran-C which I thought was deprecated in the early 2000 timeframe.

https://www.ntia.doc.gov/legacy/osmhome/EPS/openness/sp_rqmnts/radar4.html

An interesting tidbit within the article -

Radiolocation Usage and Requirements in the 300-3000 kHz (MF) Band

The radiolocation systems using the MF band are CW "lane-counting" types using the precise phase differences of several signals for determining accurate position locations. A typical application is the determination of the precise position of an oil-drilling ship in the Gulf of Mexico. Such MF radar systems have been operating for over 30 years. The private sector and the Department of Commerce's National Oceanic and Atmospheric Administration (NOAA) are the main users of CW radar systems in the MF band.

The 1605-1705 kHz band was reallocated to the broadcasting service on an exclusive basis by WARC-79. A two-part ITU regional conference subsequently planned the band for Region 2, and AM broadcasting should begin in the next few years. Sharing is virtually impossible because broadcasting signals could disturb the necessary phase precision of the CW radar systems; conversely, the possible harmful interference that the radiolocation signals can have on the broadcasting signals. The radiolocation allocation is secondary to broadcasting in the 1605-1700 kHz band, and it is expected that the radiolocation systems' use of the 1605-1705 kHz band will substantially decline because of interference problems.[EN408]

Some of the systems operating in the 1615-1700 kHz band also require a transmitted signal at the second harmonic, in the 3210-3400 kHz band. As the usage of the 1615-1700 kHz band will decline with the inception of broadcasting, use of the 3230-3400 kHz band should also decline.

According to a navigation industry executive, the MF systems operating in this band can provide a position accuracy of 5-10 meters, and the GPS system must use a DGPS for better accuracy. The DGPS can provide an accuracy from 2-3 meters. The inception of the GPS and DGPS has resulted in a 50-percent decline in MF radiolocation service usage over the past five years.[EN409] There are a large number of assignments in the 1705-1800 and 1900-2000 kHz bands, and operations can be expected at least for the next five years. Many of the systems currently operating in the 1705-1800 and 1900-2000 kHz bands will most likely continue to operate over the next five years. However, long-range spectrum requirements for the radiolocation service in the 1705-1800, 1900-2000, and 3230-3400 kHz band are expected to decrease over the next five years as activities are shifted to GPS. The requirements beyond five years are unclear, but nevertheless, are expected to decrease even more because of the increased use of GPS.
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