Lscott

The mystery continues.

It looks like there are some cell phone slot antennas up there in the photo. I doubt those are 900MHz. I wouldn't trust their response just yet.

Yeah, there is specific software for that sort of thing, CAD-AVL, Computer Aided Dispatch - Automatic Vehicle Location, applications. Acom Automax CAD.pdf Kenwood_KGP-2A_KGP-2B.pdf

Now that would start to make a lot more sense.

They have no idea whose antennas are on THEIR tower! The repeater is likely in the small block house at ground level. Maybe if you could gain access to the inside you might find some contact info on the equipment. That would save you a lot of research.

Yup, just don't expect to get the full boogie out of it.

Still getting basically sporadic noise bursts.

Closest I can tune my radio is 462.53125MHz.

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.

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 have one. Bottom right corner of photo. https://forums.mygmrs.com/gallery/image/415-amplifiersjpeg/?context=new The power output falls off outside of the Ham band. For example the DC current input at 13.8VDC with 4 watts of RF input was about 5 amps. At the GMRS frequencies it dropped to around 3 amps. I need to put it on my Bird watt meter and get a power measurement now that I got some higher power UHF slugs for it. I'm guessing I'm only getting MAYBE 20 to 30 watts at most out of it on GMRS frequencies. https://forums.mygmrs.com/gallery/image/321-bird-43-wattmeter/

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

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

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.

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 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

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.

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

I've done some technical writing for the company I work at, Power Point slide shows for training/sales, test procedures and manuals, but it's not my primary job. People think it's easy. Nope! It's boring mind numbing work and requires a lot of attention to details. People who do it full time professionally really earn their money. Doing design calculations, simulations and circuit design is much more fun, and it keeps the mind sharp too.

Yeah, programming a DMR radio is a PIA. Then again NXDN and P25 isn’t much different. I’ve done all three of the above.

Maybe. They still have to operate under US rules. Plus they need to communicate with other railroads, yards etc. That's likely going to be on VHF. Railroad - Scanner Frequencies and Radio Frequency Reference.pdf

I would not suspect the railroad. They would either be FM, or they were moving to NXDN, but that's on VHF, not UHF.

I did some checking on AAM and there is only one possible. It's an expired license and the plant is located in Three Rivers. That's a long way away. https://wireless2.fcc.gov/UlsApp/UlsSearch/licenseFreqSum.jsp?licKey=1905276 The frequency listed is 462.3125. Hum, if some radio tech miss typed the frequency entry he could have hit 462.53125, added in the extra "5" after the decimal point. Somebody could be using an unlicensed frequency, never licensed, or continues to use one on a long expired license. It happens. The FCC seems really lax in cracking down on this crap. For example the ding-dongs at the Lakeside Mall, house keeping, are doing it. They are on the same frequency as the Troy GMRS repeater but a different PL tone. Their license expired in 2015, never renewed from what I can see in the FCC database, and they still use the frequency!!! Geez!!?? Oh, if you want to "test" their, illegally operating, GMRS repeater out its 462.575MHz/467.575MHz with a PL of 186.2Hz. You can key it up about 4 to 5 miles away with an HT easy enough. Anyway you narrow the search down and locate the likely source of interference keep us informed! ULS_License - Expired Mall FCC Licenses.pdf ULS License - General Mobile Radio (GMRS) License - KAB1523 - LAKESIDE GENERAL GROWTH PROPERTIES - Administration.pdf

Gives me another frequency to look up.

Yeah, their plant is on 14 mile right next to the railroad overpass. I've been by it enough times.