Interference on 462.5325 MHZ Oakland Co Michigan

[SignallyCurious2]

I’m waiting for a call back from the SE Oakland county water authority. I’m VERY confident there’s an antenna on top of 2725 samoset AND another water tower at 3910 w Webster with an antenna and I live directly in the middle of them, straight line distance. 
 

it’s the only thing that makes sense. Especially considering it was still hammering away next door to TACOM in Warren. 

[SignallyCurious2]

21 minutes ago, Lscott said:

Weather sucks today. I don't imagine you're going out to do any DF'ing. 

I plan on confirming my water tower findings, I live for messing around in this weather haha. 

[Lscott]

2 minutes ago, SignallyCurious2 said:

I’m waiting for a call back from the SE Oakland county water authority. I’m VERY confident there’s an antenna on top of 2725 samoset AND another water tower at 3910 w Webster with an antenna and I live directly in the middle of them, straight line distance. 
 

it’s the only thing that makes sense. Especially considering it was still hammering away next door to TACOM in Warren. 

Do you have a firm read on the frequency? Also any idea about what color code, slot number and talk group is being used. If I get some time I've got my NX-1300DUK5 with me at the office today. I could add the above to the code plug and monitor it. Being at 14 mile and John-R I shouldn't have much of a problem receiving it.

[SignallyCurious2]

Just now, Lscott said:

Do you have a firm read on the frequency? Also any idea about what color code, slot number and talk group is being used. If I get some time I've got my NX-1300DUK5 with me at the office today. I could add the above to the code plug and monitor it. Being at 14 mile and John-R I shouldn't have much of a problem receiving it.

on 462.5325 T.S. 1: color code timeslot 1: 11 timeslot 2: 7 

TS 2: color code timeslot 1: 15 timeslot 2: 15

theres also another signal on 462.5375, I haven’t focused on that one too much  

 

the color codes and time slots are always changing, I’ll try to get you updated ones when you take a look, just let me know.

 

 

[SignallyCurious2]

[Lscott]

I see that "RAS" is showing up. I believe that's a Motorola specific feature to validate a radio on a trunking system. This might explain why you're having problems getting audio and multiple frequencies. If it's a trunking system there might be even more frequencies in use you haven't found yet.

https://cwh050.mywikis.wiki/wiki/Restricted_Access_to_System

[SignallyCurious2]

3 minutes ago, Lscott said:

I see that "RAS" is showing up. I believe that's a Motorola specific feature to validate a radio on a trunking system. This might explain why you're having problems getting audio and multiple frequencies. If it's a trunking system there might be even more frequencies in use you haven't found yet.

https://cwh050.mywikis.wiki/wiki/Restricted_Access_to_System

I agree, I started poking around and it turns out there are a lot of DMR systems in this area. DPD has one too which I found interesting, it was car to car audio of them BS’ing outside of the mpscs P25 system, even though they have car to car talk groups there, too. 

I’m not sure how to even begin to track down the corresponding freqs, but I feel confident that I found where it’s coming from, left the guy a VM at 8 am and still haven’t heard back.

 

[SignallyCurious2]

This popped up just now 

[Lscott]

A good resource to track down digital licenses in the FCC's database is here:

https://digitalfrequencysearch.com/index.php

If it's a trunking system on a water tower I'm going to guess it's owned and operated by a company that rents out capacity on their system to various users who don't want to put up their own repeater and or don't have the expertise to do so. A small company, with a single location, with their own repeater would typically be located on site if they have one. 

Given the frequencies and location I''m certain it had to go through an FCC frequency coordinator and should be in their database. They would need to make sure the antenna height, power level and antenna gain won't interfere with other users in the coverage area. And in this case it seems like that area is going to be rather large too.

One company would be Deltacom.

https://wireless2.fcc.gov/UlsApp/UlsSearch/licenseFreqSum.jsp?licKey=1925372&pageNumToReturn=2

https://wireless2.fcc.gov/UlsApp/UlsSearch/licenseLocSum.jsp?licKey=1925372

The closest to your frequency of 462.5325 is 462.5375. Given the tolerance of the oscillator in the SDR dongle this could be it. It's off by only 5.0KHz.

https://wireless2.fcc.gov/UlsApp/UlsSearch/licenseFreqSum.jsp?licKey=2926515&pageNumToReturn=2

https://wireless2.fcc.gov/UlsApp/UlsSearch/licenseLocSum.jsp?licKey=2926515

Here's another company.

This one is sort of odd. They are licensed state wide with a frequency range. No channel frequencies listed.

https://wireless2.fcc.gov/UlsApp/UlsSearch/license.jsp?licKey=3770395

[SignallyCurious2]

6 minutes ago, Lscott said:

A good resource to track down digital licenses in the FCC's database is here:

https://digitalfrequencysearch.com/index.php

If it's a trunking system on a water tower I'm going to guess it's owned and operated by a company that rents out capacity on their system to various users who don't want to put up their own repeater and or don't have the expertise to do so. A small company, with a single location, with their own repeater would typically be located on site if they have one. 

Given the frequencies and location I''m certain it had to go through an FCC frequency coordinator and should be in their database. They would need to make sure the antenna height, power level and antenna gain won't interfere with other users in the coverage area. And in this case it seems like that area is going to be rather large too.

One company would be Deltacom.

https://wireless2.fcc.gov/UlsApp/UlsSearch/licenseFreqSum.jsp?licKey=1925372&pageNumToReturn=2

https://wireless2.fcc.gov/UlsApp/UlsSearch/licenseLocSum.jsp?licKey=1925372

The closest to your frequency of 462.5325 is 462.5375. Given the tolerance of the oscillator in the SDR dongle this could be it. It's off by only 5.0KHz.

https://wireless2.fcc.gov/UlsApp/UlsSearch/licenseFreqSum.jsp?licKey=2926515&pageNumToReturn=2

https://wireless2.fcc.gov/UlsApp/UlsSearch/licenseLocSum.jsp?licKey=2926515

Here's another company.

This one is sort of odd. They are licensed state wide with a frequency range. No channel frequencies listed.

https://wireless2.fcc.gov/UlsApp/UlsSearch/license.jsp?licKey=3770395

I’ve been working with the gentleman at delta com on this, he is also actively working to identify the signals, his transmitters are 25w and the nearest is in Southfield. 
 

ill look some more, still waiting to hear back from the general manager of the water tower who is responsible for its operations. The only licenses I found were for ATT on that water tower. 

[Lscott]

22 minutes ago, SignallyCurious2 said:

I’ve been working with the gentleman at delta com on this, he is also actively working to identify the signals, his transmitters are 25w and the nearest is in Southfield. 
 

ill look some more, still waiting to hear back from the general manager of the water tower who is responsible for its operations. The only licenses I found were for ATT on that water tower. 

This is turning out to be a bit of a real mystery. I wondering now if the owner even licensed the frequency, and not just stuck up their repeater and said screw the FCC. I'm getting the feeling there is a lot of crap out there on the air that isn't properly licensed and the FCC just ignores it until somebody complains. That's not how it's supposed to work.

[MarkInTampa]

42 minutes ago, Lscott said:

 

The closest to your frequency of 462.5325 is 462.5375. Given the tolerance of the oscillator in the SDR dongle this could be it. It's off by only 5.0KHz.

 

The closest is actually 462.53125, same company (Deltacom) and licensed for trunk service. It's only .13 KHz down. Also 462.5325 isn't standard spacing, FCC only shows 2 experimental licenses in the the entire country and 100's licensed for 462.5312 I'd vote the oscillator is a bit off. With a SDR dongle using SDRSharp and Simple DMR decoder, I can decode DMR +/- 1KHz easy.

[Lscott]

3 minutes ago, markskjerve said:

The closest is actually 462.53125, same company (Deltacom) and licensed for trunk service. It's only .13 KHz down. Also 462.5325 isn't standard spacing, FCC only shows 2 experimental licenses in the the entire country and 100's licensed for 462.5312 I'd vote the oscillator is a bit off. With a SDR dongle using SDRSharp and Simple DMR decoder, I can decode DMR +/- 1KHz easy.

Good point. I think once the correct frequency is nailed down looking it up in the FCC's database would yield results.

[Lscott]

12 minutes ago, markskjerve said:

I'd vote the oscillator is a bit off.

The oscillator in the repeater also could be off frequency a bit too. I have heard of some repeaters where they use an OCXO, Oven Controlled Crystal Oscillator, for very high frequency accuracy.

I think the cheap SDR dongles use a simple TCXO, Temperature Compensated Crystal Oscillator, module. The usual specifications for those are +/- 0.5 PPM, Parts Per Million, frequency accuracy more or less.

Usually portable or battery operated equipment use the TCXO module since the power requirements are way to much due to the electrically heated oven on an OCXO module.

Understanding Ovenized Oscillators.pdf

[MarkInTampa]

8 minutes ago, Lscott said:

The oscillator in the repeater also could be off frequency a bit too. I have heard of some repeaters where they use an OCXO, Oven Controlled Crystal Oscillator, for very high frequency accuracy.

I think the cheap SDR dongles use a simple TCXO, Temperature Compensated Crystal Oscillator, module. The usual specifications for those are +/- 0.5 PPM, Parts Per Million, frequency accuracy more or less.

Usually portable or battery operated equipment use the TCXO module since the power requirements are way to much due to the electrically heated oven on an OCXO module.

Understanding Ovenized Oscillators.pdf 126.47 kB · 0 downloads

I have first hand experience with the SDR being slightly off frequency. I picked up a DMR HT awhile back and the strongest DMR repeater I could pickup showed as 443.188 on the SDR and couldn't find it listed anywhere to program the HT. Also searched a bit and above the frequency online and couldn't find it anywhere. I mentioned it to one of the area guys I talk to on D-Star also is really into DMR and he found that the frequency was actually 443.1875 and he got the ID. He ran the ID and got one single hit on it on the internet - on one of the area club's webpage that also showed all the programming information and talk groups. It's not listed anywhere else. I learned not to put a lot of faith with the SDR being spot on.

[SignallyCurious2]

21 minutes ago, Lscott said:

The oscillator in the repeater also could be off frequency a bit too. I have heard of some repeaters where they use an OCXO, Oven Controlled Crystal Oscillator, for very high frequency accuracy.

I think the cheap SDR dongles use a simple TCXO, Temperature Compensated Crystal Oscillator, module. The usual specifications for those are +/- 0.5 PPM, Parts Per Million, frequency accuracy more or less.

Usually portable or battery operated equipment use the TCXO module since the power requirements are way to much due to the electrically heated oven on an OCXO module.

Understanding Ovenized Oscillators.pdf 126.47 kB · 0 downloads

 

I’ve been doing the SDR stuff since 2015, and im using a RSP1A, and have also confirmed through various other signals, I am calibrated correctly and am using hands down the most robust SDR decoding software freely available SDRTrunk v6.1
 

the facts of the matter are: 

its not delta com

its not on center with any frequency it should be

its an encrypted DMR trunked repeater 

its causing interference with GMRS

Its causing interference with delta com licensed frequencies for their own subscribers in the area

It’s more than likely originating from the water tower south of American axle at 14 mile and Coolidge

It’s either intermod or not licensed transmitter

 

[SignallyCurious2]

2 minutes ago, markskjerve said:

I have first hand experience with the SDR being slightly off frequency. I picked up a DMR HT awhile back and the strongest DMR repeater I could pickup showed as 443.188 on the SDR and couldn't find it listed anywhere to program the HT. Also searched a bit and above the frequency online and couldn't find it anywhere. I mentioned it to one of the area guys I talk to on D-Star also is really into DMR and he found that the frequency was actually 443.1875 and he got the ID. He ran the ID and got one single hit on it on the internet - on one of the area club's webpage that also showed all the programming information and talk groups. It's not listed anywhere else. I learned not to put a lot of faith with the SDR being spot on.

I run the same setup at home pulling in all the P25 traffic from macomb, Wayne and Oakland county, 120,000 calls per day with a 99% decode rate, proper SDRs with proper software are

[Lscott]

36 minutes ago, SignallyCurious2 said:

 

I’ve been doing the SDR stuff since 2015, and im using a RSP1A, and have also confirmed through various other signals, I am calibrated correctly and am using hands down the most robust SDR decoding software freely available SDRTrunk v6.1
 

the facts of the matter are: 

its not delta com

its not on center with any frequency it should be

its an encrypted DMR trunked repeater 

its causing interference with GMRS

Its causing interference with delta com licensed frequencies for their own subscribers in the area

It’s more than likely originating from the water tower south of American axle at 14 mile and Coolidge

It’s either intermod or not licensed transmitter

 

I would trust Delta Com if they say it's not them.

So Delta Com is saying they are experiencing interference too? A complaint to the FCC from them may trigger some response since they are a business paying for the spectrum they use.

I would like to know what the water tower people have to say about it, if that's the antenna and source.

Maybe it a rouge Chinese Repeater. Keep us updated. It might end up like a knit sweater. You find the end of the thread and start yanking on it. Soon the whole thing starts to unravel.

[SignallyCurious2]

3 minutes ago, Lscott said:

I would trust Delta Com if they say it's not them.

So Delta Com is saying they are experiencing interference too? A complaint to the FCC from them may trigger some response since they are a business paying for the spectrum they use.

I would like to know what the water tower people have to say about it, if that's the antenna and source.

Maybe it a rouge Chinese Repeater. Keep us updated. It might end up like a knit sweater. You find the end of the thread and start yanking on it. Soon the whole thing starts to unravel.

I agree. Deltacom is actively helping me track it down too, they appreciate my investigative work, we’re talking about going in on a KrakenSDR together 

I’ve called the water authority twice, the second time explained the situation to the secretary of the guy I’m looking for, they leave them office at 3pm so who knows. 
 

im datalogging all the decoded message blocks into text format with date time groups to get a good idea of the times they’re most active to be better positioned to track it down. There’s 2 hour gaps in the middle of the day where the channel isn’t used, then used for 20 min continuously then not again till the next day. Very sporadic and making pinning it down difficult. 

[Lscott]

For the moment I have my cheap tri-band radio tuned for 462.5325MHz before screwing around with my DMR radio. I am getting sporadic bursts, mostly noise. The building I'm in has metal mesh in the concrete walls so its a bit of a Faraday cage. However every-once in a while I can make out the TDMA pulsing.

Water Tower In Question - 2852 Samoset Rd - Google Maps.pdf

This is the water tower right behind the AAM plant.

[SignallyCurious2]

 

5 minutes ago, Lscott said:

For the moment I have my cheap tri-band radio tuned for 462.5325MHz before screwing around with my DMR radio. I am getting sporadic bursts, mostly noise. The building I'm in has metal mesh in the concrete walls so its a bit of a Faraday cage. However every-once in a while I can make out the TDMA pulsing.

Water Tower In Question - 2852 Samoset Rd - Google Maps.pdf 2.34 MB · 1 download

This is the water tower right behind the AAM plant.

I had the best luck at 462.53188 as a “center”

[Lscott]

5 minutes ago, SignallyCurious2 said:

I had the best luck at 462.53188 as a “center”

Closest I can tune my radio is 462.53125MHz.

[Lscott]

Still getting basically sporadic noise bursts.

[SignallyCurious2]

26 minutes ago, Lscott said:

Still getting basically sporadic noise bursts.

SOCWA with the water tower called back, it is not them but they’re also interested and going to help out. 
 

That’s how the transmissions are for me too, most of them data, very very few actual calls more than 1.2 sec. Latest call so far was 4:45pm.

[MarkInTampa]

5 minutes ago, SignallyCurious2 said:

SOCWA with the water tower called back, it is not them but they’re also interested and going to help out. 
 

That’s how the transmissions are for me too, most of them data, very very few actual calls more than 1.2 sec. Latest call so far was 4:45pm.

If I had to guess they are running MotoTrbo GPS tracking on the radios. The GPS system can be programmed to poll the radios every 10 minutes or every 1 kilometer of movement. They are short bursts, around 600ms to 1 second. If a car is moving it sends a lot more traffic than if it doesn't.