Mobile Data (MDT Decoding)

[SKYNET156]

I have recently aquired a MW-500 with an 800mhz RIM (Radio Interface Modem)
My local fire department uses MDT's on 800mhz conventional analog, is it legal to decode that? and what type software do i need to decode if it is legal?

 

[DaveNF2G]

It's legal to decode non-encrypted MDT traffic anywhere in the USA except Texas.

 

[gary123]

There are numerous MDT data formats. it often looks like every service uses thier own protocall. I would start with a simple txt decoder and work my way up through more complex protocalls such as ascii, mcd, and any other protocalls you can find. You should look at both widows and linux based programs.

Decoding mdts is an interst for many enthusiasts but there is veryy little posted on this topic. often because the terminals are encrypted (or are believed to be encrypted).

 

[SKYNET156]

thanks for all the good information,

I was unsure about the protocall, but i know it's not an encrypted frequency, i compared the MDT Data with different encryption protocall's and it's not encrypted from what i can here, i am wondering now what the fire dept uses it for?
I'd never do a police MDT

 

[WV8VFD]

i am wondering now what the fire dept uses it for?

Often times it includes the call address, call details, mapping, and any notes the call taker or dispatcher puts in.

 

[dracer777]

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Any ideas if weld or boulder county are encrypted? This would be very cool to have.

 

[SKYNET156]

you would have to listen and be able to dicenerate between encryption and data, most encryption has alot of similiar sounds, while data burst you can automatically tell the difference, thats how i found out, and then for $60 i went on ebay and purchased an MW-500

 

[gary123]

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Any ideas if weld or boulder county are encrypted? This would be very cool to have.

I dont know and am not really interested as decrypting an encrypted transmission is a no-no just about everywhere. That being said because of the numerous ways that data can be coded (not encrypted) this is the reason many believe MDTs are encrypted, often (not always) the system is in the clear but the wrong protocall decoder is being used.

many EMs, FD and other services like taxis and couriers use MDT or MWS (same thing as far as we are concerned) the info can contain dispatch time, date and details , gps info, call history (like previous times at that location). mapping info all kinds of cool things.

I would love to see a MDT decoding thread here but because of the sensitive nature of these devices I agree with the site administrators and moderators and dont expect to see such a thread starting or being accepted. It is possible that a MDT data identifcation thread may be acceptable, such a thread (if acceptable) may have a SMALL sound byte (5 sconds or so) along with a descriptor such as plain text ascii or what ever so that someone may be able to compare the sound of thier local system with a known example of a similar system. I believe there are similar threads for HF and other data protocalls.

 

[poltergeisty]

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Any ideas if weld or boulder county are encrypted? This would be very cool to have.

I know Loveland uses MDT which seems to be cell phone based. i.e CDMA. Sense the system uses CDMA, I wonder if it would be further encrypted? Now that I think of it - I know of a certain haxxer group that successfully decode such a system.

 

[AZScanner]

I've got a bit of experience with this. A terminal and a modem isn't the right way to go about this. Here's why:

What a terminal/modem does is sample the frequency in use looking for data addressed to ITSELF. If the data is not addressed to your terminal, guess what? It will ignore it. And odds are good that there are no terminals on the system with the same ID as you, so you'll get squat for your efforts. To make matters worse, MDC programs and/or MDT firmware will require you to "log in" to the system before the terminal starts listening for messages. So to recap you have to have the same ID as the terminal you're trying to monitor AND be on the same frequency AND log in as the same user. Good luck.

What you need is an app that will decode the protocol and display ALL messages, not just the ones assigned to it. Think PDW, which is a popular windows based data decoder - it simply monitors the frequency you feed it, displaying whatever it comprehends. The trick part here of course is the protocol - you need to know what they're using before you can take a crack at decoding it. There's been some interesting work done with GNU radio in regards to RD/LAP decoding, which is the protocol most Motorola mobile data systems use these days. I'd love to give it a whirl but the hardware required to do it is about $700 which is simply too high for me to justify snooping around on MDT channels. I still haven't got off my lazy butt yet and set up a Linux box for DSD to run on!

If you get the terminal and model thing up and running and actually decoding, I'd love to hear about it, but for the reasons stated above, I think you've bought yourself a neat little toy for display but not much else.

Good luck,
-AZ

 

[SKYNET156]

I have yet to collect all the parts for this project,
I have the MDT and an 800mhz Radio Interface Modem, i just need to get an astron power supply and an antenna for the MDT Modem,
If all else fails, i am going to mount it in my car and just use the touch screen for navigation, maps and music, and maybe get a Wi-Fi antenna, As far as software, i am going to look into the Windows Software mentioned above, but it's something i can only work with on the weekends because of my job, but anyother suggestions would be appreciated, i would like to get my hands on a VHF RIM and decode a local taxi/towing company that are the same company, i peeked inside the tow truck and they have newer MDT's but i saw a Motorola VRM modem mounted on the lower dash...so i would like to take a look at that and see if anything interesting comes of it.

 

[AZScanner]

I have yet to collect all the parts for this project,
I have the MDT and an 800mhz Radio Interface Modem, i just need to get an astron power supply and an antenna for the MDT Modem,
If all else fails, i am going to mount it in my car and just use the touch screen for navigation, maps and music, and maybe get a Wi-Fi antenna, As far as software, i am going to look into the Windows Software mentioned above, but it's something i can only work with on the weekends because of my job, but anyother suggestions would be appreciated, i would like to get my hands on a VHF RIM and decode a local taxi/towing company that are the same company, i peeked inside the tow truck and they have newer MDT's but i saw a Motorola VRM modem mounted on the lower dash...so i would like to take a look at that and see if anything interesting comes of it.

Download PDW, set it to decode FLEX and feed it audio from a discriminator tapped scanner while searching 928-931 MHz. You might be in for a surprise depending on how many agencies in your area use pagers for dispatching calls.....

-AZ

 

[DaveNF2G]

Many agencies in the northeast use commercial POCSAG text paging.

 

[poltergeisty]

To think my small town uses MDT and pagers... :lol:

 

[gmclam]

Download PDW, set it to decode FLEX and feed it audio from a discriminator tapped scanner while searching 928-931 MHz. You might be in for a surprise depending on how many agencies in your area use pagers for dispatching calls.....

I did d/l PDW, and I did search the bands, and I did find one frequency that is dispatching "calls". But it was/is on VHF high. Very interesting indeed.

I was not able to recognize the data transmissions I found in the 800 & 900 MHz bands. It would be very helpful if we could all post samples of what each protocol sounds like. The signal I had good luck with from VHF is FLEX 1600, but the topic of this thread is MDT decoding. Is one protocol more common than others for MDTs?

 

[n7lxi]

there's some good samples of what POCSAG and Flex sound like here: Digital Modes Samples

 

[danbrannan]

thanks

i am studying a thread from a year ago about this to learn more. sorry if my last post was cut short. i am surprised i never found this site before. it rocks.

 

[SCMajorInci]

Pdw

I also use PDW to decode freqs. I would also recommend scanning 150.000 - 160.000 as our local police/fire use 158.895 POCSAG. I have a scanner dedicated to just decoding information.

 

[kb1ipd]

Sorry for resurrecting such an old threat, but this seemed the most relevant to what I was looking for.

I've been looking at the various formats out there, trying to ascertain how common they currently are.

It seems some departments are now moving to contracting with wireless companies (Sprint, Verizon, AT&T etc) and just using commercial 3G and 4G for many of their MDT's.

However, that's certainly not all of them.

Some use Flex, despite it being primarily a paging format.

Others (none in my area that I can find) use Mobitex. If they do in my area, maybe I'm looking at the wrong frequencies.

Is MDC4800 still in use much?


Also, does anyone know if many departments are using systems like APCO P25, Provoice etc. Most of these digital voice modes also have data capabilities. I'm not sure to what extent the data modes on these formats is used.

 

[DaveNF2G]

Just an FYI. The version of "Flex" being used for two way communication is probably something called ReFLEX. You might be able to dig up more info on that name.