1.776mhz LSB data signal

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linuxusr47

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I need help identifying a signal on about 1.776mhz. It is a data signal and is best heard on LSB. Here you can hear the signal: http://pages.suddenlink.net/k5oai/audio/1736noise.mp3 I tuned slightly off the center so the intermittent tone is audible.

Here is the history of this signal. As of Nov 1, 2009 I started having an increased noise floor on my receivers that covered from 1.710mhz - 5.0mhz. (By noise floor I mean the usual atmospheric hiss that I hear on the receiver) My usual noise floor was from an S3 to an S7 depending on the frequency. Now it is an S9+5 or more. This makes listening on 160m impossible as most signals I receive (when the noise floor is not that high) are copied about S5-S9.

I traced the signal's originating source down to the 1.776mhz data signal.
After a week (Nov 1-8) the signal went silent for a week.
So I had my normal noise floor and nice quiet listening from Nov. 9-15.
Monday Nov 16 it was back and is still there today Nov 21.
There are a number of 160m contests coming up in the next month(s), so I am hoping to find/fix this problem soon.

Clues that I have gathered so far.
The 1.776mhz signals are loudest during hours of darkness.
About 15-20 minutes before daylight the data signals drop from S9+10 to S7-S9 and the noise floor also drops some, but continues to be 3-5 S units higher than it should be. Forcing me to listen only to signals above 5.5mhz where the noise has dropped back to my normal noise floor.

All I have been able to search out is that, the range of frequencies are allocated to:
"1.705 - 1.800 Fixed Service Land/Mobile/Marine "

I live in a 2 room apartment on the bottom floor and external antenna possibilities are extremely limited, as are any kind of large indoor loops.

Any help identifying the signals so I might speak with those that are doing the transmitting would be helpful. I have lived here for 4 years and use 160m daily, so I know this is a new transmitter. Also there is no BPL here in our area.

Thank you for any help with this problem.
 

k9rzz

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Well, if that digital signal is fading in and out with darkness, then it's no where near you. You don't mention what receiver you have, but I really doubt that this digital signal has anything to do with a rising noise level at your location, that's a different ball game. Thanks for posting your logging, it could be an ocean beacon of some sort, maybe someone else can hear it too.
 

linuxusr47

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I would tend to agree about the data signal and the noise floor not being related, however when the data signal stopped for that week, the noise floor also dropped back to normal?

Receiver(s) used were Kenwood TS-450SAT and Elecraft K2. Main antenna was a Hi-Q 5/160 @ 20 feet on a tar and gravel roof, with 16 radials each 13 foot long. Picasa Web Albums - k5oai.sam - RoofTopAntenn...

Identifying what kind of telemetry signal (mode) it is, might help me decode it and determine who/where it is coming from.

Thanks for your reply.
 

js_scan888

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It could be Cochrane Technologies Inc:
ULS License - Land Mobile Radiolocation License - WPHW222 - COCHRANE TECHNOLOGIES INC - Frequencies Summary

According to their website:
Navigation

They operate and maintain permanent Mirconet reference stations for complete coverage of the Northern Gulf of Mexico.

Their radio beacons send out range correction data in RTCM SC-104 format or custom format.

Spectrum Labs Digimode Terminal can decode the RTCM SC-104 MSK signal at 100 or 200 baud.
Another program, DSCdecoder, might also be able to handle the format.
 

MSM_Maria

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Unfortunly the record has bad quality, low SNR and mp3 format, and the signal hadn't got fully into reciever bar, in other words, the signal is cutted.
But this signal isn't noise, this signal is the classical multichannel data trasmission.
It is very hard to define by this record What system is that and which parameters of transmission it has.

If You will get better record of this signal, it will be possible to define parameters of system, and after to identificate the signal.


thanks for interesting topic, it is an interesting signal.

Best regards.
 

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linuxusr47

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If You will get better record of this signal, it will be possible to define parameters of system, and after to identificate the signal.
I recorded an I/Q, wave file, which will play in Rocky but it is 42mb and I can't upload it to my limited web space. Do you have a place I could upload it?

linuxusr47
 
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Hooligan

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Just thinking out loud here...

Could it be a second harmonic of a mediumwave broadcaster using NRSC-5 or DRM, or a 4th harmonic of a DGPS transmitter??

I base this on your mentioning of either an ERP drop or change in antenna pattern at little before dawn.

LORAN-A operated in that range, but I guess they're out of action.

You say there's no BPL in your area yet, but I'd still spend just as much time treating it as EMI as you are in treating it as a legit but unidentified emitter.

I assume you've tried powering your receiver via battery, and turning off the main circuit breaker in your home to eliminate the target as being very local EMI/RFI...


Why not contact Cochrane technologies & see what they have to say? They should be interested because if it's not their emitter, the emitter you're hearing could be causing interference to their system now or in the future. I suggest you just tell them you're curious & trying to track the mysterious signal down & not call it "interference" if you want some cooperation from them :)

Licensee
COCHRANE TECHNOLOGIES INC
3913 HWY 90 E
BROUSSARD, LA 70518
ATTN DOUGLAS A COCHRANE JR


P:(318)837-3334
F:(318)837-7134
E:joey@cochranetech.com
 

linuxusr47

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I assume you've tried powering your receiver via battery, and turning off the main circuit breaker in your home to eliminate the target as being very local EMI/RFI...
I did all of the above. I believe the data signal is coming from somewhere else due to it's dark hours propagation characteristics.

Why not contact Cochrane technologies & see what they have to say? They should be interested because if it's not their emitter, the emitter you're hearing could be causing interference to their system now or in the future. I suggest you just tell them you're curious & trying to track the mysterious signal down & not call it "interference" if you want some cooperation from them :)
I already did that and received an automated reply that he will be out of contact until after Thanksgiving. So we will see then what happens. If it is his equipment, I believe it may be off frequency from what his license states.

linuxusr47
 

kb2vxa

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One source of your frustration is the fact that Amateur Radio is the only service that transmits LSB, everything else is USB. Another is that in order to decode digital signals your receiver must be set to USB except in very rare cases and that's when you use the "invert" function of the software. What may be confusing you is the bandwidth of the signal, ask yourself if you're using the correct filter to hear all of it.

Keeping that in mind, using a low capacitance probe or "gimmick", a scope connected to the IF ahead of any filtering or highly selective circuits will give you the full spectrum of what you're looking at. Software analysis will only tell you what you're hearing after filtering and demodulation, you want to look at the RF signal. Once that has been determined you can use a narrow IF passband and tuning across you may analyze each individual component either with the scope or appropriate software.
 

zz0468

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I'm currently hearing a carrier being keyed on and off, with a slight frequency shift before it unkeys. It's zero beat at 1776.2 KHz.

A google search of that frequency shows a number of references to meteorological data from buoys, drift net beacons, and various other similar things.
 

linuxusr47

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I/Q file uploaded

I recorded an I/Q, wave file, which will play in Rocky but it is 42mb and I can't upload it to my limited web space. Do you have a place I could upload it?
Thanks to MSM_Maria for pointing me to RapidShare as a site I could upload the file to.
So if you wish to listen to rocky-1.776data.wav it can be found here:

RapidShare: 1-CLICK Web hosting - Easy Filehosting

MD5: 996655A6FCA2C34EA40563149E917A12

I hope the recording is such that identification will be possible.

TIA
linuxusr47
 

MSM_Maria

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I'm very sorry for such big delay with my reply, i hadn't ability to be online for some time.

Huge thanks linuxusr47, for Your link in rapishare, today Your file will be downloaded.

After it will be downloaded and analyzed, I will post results of analysis.

With best regards, Maria.
 

MSM_Maria

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First of all i would like to thank You for very interesting signal it is rare enought, and also for I/Q record.

After some analysis:

Picture 1

General view

Picture 2

The signal itself, BandWidth is about 2200Hz

Picture 3

Baud Rate 1800Hz

Picture 4

The signal in second degree, very characteristic lines


Picture 5

We can observe hard 7bit frame, it may be start-stop transmission.


Learning Combination of all parameters of this signal, I'm sure on 99,99% that it is GMSK with speed 1800 bd. Most probably this is transmission of some telemetry or something like that. Relation noise/signal is bad, but I/Q record allows to define main parameteres of the signal surely enought.

Hard frame structure of transmission creates illusuion of multichannel presense, but it is only illusion.

unfortunly, it is hard to say exactly what protocol is used here, because the signal is very rare.

Many thanks for interesting signal and topic.

With best regads, Maria.
 

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