MDT channels and voice?

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paulmohr

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I was under the impression MDT was a term for the computers in the cars that they use to look up information on someone. They are very cool, I have seen one in use. I was sitting in police car last winter waiting for a tow truck and they showed me how it worked. They pulled up my arrest record, mug shot and all kinds of other info right in the car. Even checked to see if I had any warrants, thank god I didn't lol.

So if they are a data channel, why am I starting to receive voice transmissions on the Lenawee county and Monroe county Sheriff MDT channels? It just started happening today. There is a 3 day country music festival at MIS speedway this weekend. So maybe they are using these channels to cover that event? I see the county EMS group has its own MIS channels. And they are hopping with chatter today. I assume they have them specifically set up to cover the races when they are here.

And the MTD channels are on 460.00mhz and sound like crap. Very scratchy like they are very far away. Real low RSSI numbers too, like 4 or 5 hundred when most other channels are closer to 950. I would guess these are fairly far away and/or my antenna kind of sucks at 450mhz?
 

mmckenna

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In the old days, MDT's ran on a "regular" radio channel. That really limited data speeds. It was good enough for slow speed data, things like text, simple documents, etc.
When better technologies came along, ones with more bandwidth, the ability to pass photos, more info, etc. made it a much more attractive option.
Some agencies use cellular/LTE service from one of the large carriers.
With FirstNet LTE hitting the airwaves soon, it's going to be even easier for agencies to switch to this.

Probably what you experienced was them switching from the old UHF MDT system to a newer cellular based system. That allowed them to reuse the old MDT channel as another voice channel.

As for why you don't pick them up as well, that could be any number of things, including your location, antenna, their system, etc.

I remember back in the very early 80's my uncle, who was a sergeant, had an MDT in his patrol car. Back then only the sergeants had them, everyone else had to do their plates through dispatch. Anyway it was very slow speed, you could see the individual characters being printed across the screen as they came in. He could run plates, licenses, etc. No photos back then. There was even a rudimentary "football" game he could play on the terminal.

If you want to see what the future will be bringing, look up FirstNet LTE. It'll be a nation wide LTE network dedicated for public safety. AT&T has the contract to run it, and the are building it out now. It'll change public safety communications quite a bit.
 

W8RMH

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There is some interesting technology out there. In the city where I live all the cruisers have video cameras mounted on them and they can scan every license plate they pass. The MDT automatically checks the state and national databases for stolen/wanted vehicles, etc.
 

paulmohr

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The one they showed me was pretty impressive. I think it was a State Patrol car. If not it was a sheriff. I know it wasn't a local town cop. My car got stuck down the road in the snow and they pulled in my driveway to see if I knew who's it was. I told them it was mine and I was trying to find someone who could help me tow it home. They said it had to be moved NOW because wasn't completely off the road and there was snow emergency coming. So they called me a tow truck and let me wait in their car while it showed up. Not only could they pull up who I was, my social information, criminal record, DL photo, mug shots but they also knew why I went to jail and that I had mental problems and was possibly suicidal. Also any aliases or if I was known to carry a weapon or had one registered to me.

the one trooper said, "oh, I see you have been arrested twice for contempt of court, bailed out once and spent 45 days on the other. My guess is it was child support huh.". I was like yep, I had to pay 1500 or do 45 days and I didn't have the 1500 lol. And somehow they knew I was going to CMH so they wondered what mental problems I had and if I was ok at the moment. Pretty useful systems, I am glad they are updated them.
 

jonwienke

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MDTs do not run on voice channels any more. They use cellular data / wifi style technology, which is much wider bandwidth than voice channels, and thus offers faster data transfer rates. mmckenna is probably right, the frequency has been repurposed to voice use after the agency switched to a cellular MDT data provider.
 
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