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Author Topic: Looking at 1710 kHz with Carrier Sleuth  (Read 467 times)

Offline ChrisSmolinski

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Looking at 1710 kHz with Carrier Sleuth
« on: December 25, 2019, 1556 UTC »
Carrier Sleuth generates very high resolution waterfalls from I/Q recording files made by several SDR (Software Defined Radio) programs. It's a powerful tool for detecting very weak MW stations that you cannot necessarily hear. And it can be used to "fingerprint" station carriers for identification purposes.

More details and downloads here:
https://www.blackcatsystems.com/software/medium_wave_carrier_display_app.html

I examined 1710 kHz with Carrier Sleuth, using SDR recordings from roughly 1700 UTC 24 December 2019 - 1430 December 25 2019. Here's the high resolution waterfall it produced:



I used my AFE822x SDR to make the recordings, it's A/D clock is not locked to GPS so it can drift and have errors. When I spot checked 10 MHz WWV this morning it was reading 12 Hz high, so at 1710 kHz the frequencies would be 2 Hz high. the antenna was my new 120 ft T2FD.

At the beginning of the waterfall we can see three carriers. I believe the center one (1710.008 kHz) is the Flight 93 TIS (or at least one of them, apparently it has two transmitters).

Just before 2100 UTC we see what I believe to be Radio Corsair's transmitter (1710.0025 or so) appear and disappear a few times. I believe this was him tuning up in preparation for the later show.

At 2142 UTC a transmitter is turned on. You can tell it was turned on and was not fading in due to the frequency drift. This is fairly characteristic of most transmitters when they either turn on or change power levels, due to thermal effects on the oscillator. This settles to 1710.0073 or so, and then goes QRT at 2240 UTC.  But it's not Radio Corsair, because they signed on at 2208 UTC, which can be clearly observed. I assume this was another pirate?

Another carrier appears on 1709.991 at 2240 UTC. There is no drift. Same transmitter we observed above, but something changed the frequency. It's weaker also, so maybe lower power? Off at 2300 UTC.

Radio Corsair signs on at 2208 UTC, drifts a little, and ends up on 1709.996 kHz, and goes QRT at 0208 UTC, which matches the audio I heard.

Another transmitter appears at 0144, and drifts down to 1710.007 kHz or so, tough to tell. It sure looks like the one that appeared earlier at 2142 UTC.

There's another transmitter that appears at 0208 UTC around 1709.990 kHz and goes off 0213 UTC. Radio Corsair again? It's weaker than their previous signal, so perhaps someone else.

There's a zoo of other carriers that appeared overnight. The strong signal from Radio Corsair made it difficult to see them when it was on the air, another night's observations might shed some light on them. There are quite a few TIS stations on 1710, plus of course who knows how many pirates.

Many of the 1710 kHz TIS stations (as well as TIS stations on other frequencies) are operated by the Federal government, and do not appear in the FCC database. I filed a FOIA request and obtained information about these stations, which is incorporated into my DX ToolBox program for Windows and macOS (along with lots of other useful information and tools). I believe this is the only public source for these TIS stations. Information and downloads for DX ToolBox are here:
https://www.blackcatsystems.com/software/ham-shortwave-radio-propagation-software.html

Here's the TIS stations that appear on 1710 kHz. I suspect some of these are the weak carriers observed on the waterfall:


Stations fade out as expected around sunrise, leaving the Flight 93 station(s), as well as probably Hudson County NJ and Springfield MA as the last to go.



Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
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Offline ChrisSmolinski

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Re: Looking at 1710 kHz with Carrier Sleuth
« Reply #1 on: December 25, 2019, 2050 UTC »
A bit of an update. I've been checking 1710 kHz, and I believe the Flight 93 TIS is 1710.007 kHz, and Hudson County is 1710.005 kHz (note my AFE822x is reading about 2 Hz high at 1710 kHz, so I adjusted the values), based on what the carrier frequency is depending on which of the two stations I am hearing.

I also believe that the station that came on and went off a few times (2142 UTC and 0144 UTC) may have been the Hudson County TIS. The frequency it settles to matches them, and they have been having technical difficulties for quite a while.

1710.021 kHz may be the Springfield MA Armory TIS? Just a guess.

p.s I just updated Carrier Sleuth to version 1.2.0, adding a ppm correction.
« Last Edit: December 25, 2019, 2220 UTC by ChrisSmolinski »
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 900 ft horizontal loop / 500 ft northeast beverage / 58 ft T2FD / 120 ft T2FD/ 300 ft south beverage / 43m / 20m / 10m  dipoles / Crossed Parallel Loop / Discone in a tree

Offline NJQA

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Re: Looking at 1710 kHz with Carrier Sleuth
« Reply #2 on: December 26, 2019, 1320 UTC »
This is fascinating to me.  This is a good transmitter fingerprinting tool.

Many years ago we would identify multiple carriers on a frequency by using Sub-Audible Heterodynes (SAH).  If two carriers were on the same frequency and differed by a small amount, your S-meter would show a small periodic oscillation up and down.  If it did this twice a minute, the two carriers differed by two hertz.  You had to factor out variations due to propagation and if there were multiple signals there it was hard to tell anything useful, but it worked somewhat.

You do exactly the same thing when calibrating your boat anchor frequency marker to WWV.   At some point you would no longer be able to hear an audible beat note and you would look at the S-meter for that point at which the small variations stopped.

Back in the seventies I would hear AM radio stations perform periodic frequency checks by broadcasting a tone and an independent lab some distance away would measure their transmit frequency.  It always amazed me that they could do this on graveyard channels where dozens of carriers were simultaneously present.  I donít know how they did this, but I suspect that the audio tone they transmitted must have been accurate to less than a hertz.  The remote lab probably zero beat that tone on either the upper or lower sideband, measured the actually RF frequency of the tone, and by subtracting out the audio tone frequency would have the transmitted carrier frequency.  Thatís my guess...if any of you station engineers can provide further insight I would be interested.  I donít know how they accounted for frequency variations due to skywave effects.

Offline nhp

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Re: Looking at 1710 kHz with Carrier Sleuth
« Reply #3 on: May 23, 2020, 1614 UTC »
Hi Chris,

Is there any update coming on Carrier Sleuth Windows please?   It's a very useful program, but the present version has expired...

Thanks.


Offline ChrisSmolinski

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Re: Looking at 1710 kHz with Carrier Sleuth
« Reply #4 on: May 23, 2020, 2205 UTC »
Hi Chris,

Is there any update coming on Carrier Sleuth Windows please?   It's a very useful program, but the present version has expired...

Thanks.

I am working on a new update to Carrier Sleuth now in fact, I hope to have something out in a day or two, testing it now.
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 900 ft horizontal loop / 500 ft northeast beverage / 58 ft T2FD / 120 ft T2FD/ 300 ft south beverage / 43m / 20m / 10m  dipoles / Crossed Parallel Loop / Discone in a tree

Offline ChrisSmolinski

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Re: Looking at 1710 kHz with Carrier Sleuth
« Reply #5 on: May 28, 2020, 1607 UTC »
Carrier Sleuth 1.3.0 is now available for download: https://www.blackcatsystems.com/software/medium_wave_carrier_display_app.html
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 900 ft horizontal loop / 500 ft northeast beverage / 58 ft T2FD / 120 ft T2FD/ 300 ft south beverage / 43m / 20m / 10m  dipoles / Crossed Parallel Loop / Discone in a tree