Police Monitoring

[john3190]

Are all Maryland police agency radios channels encrypted? Or are there still scanners out there that will pick them up?

 

[Danny37]

Any agency in particular? If you search in the database and you see "E" or "e" it means the frequency is full-time encrypted or partially encrypted for the lower case "e"

 

[john3190]

Thanks for the info. Mostly looking into state police or county frequencies. May he moving to maryland in a few months and just trying to figure out if it is worth buy another scanner if it won’t work for anything after I move

 

[maus92]

Thanks for the info. Mostly looking into state police or county frequencies. May he moving to maryland in a few months and just trying to figure out if it is worth buy another scanner if it won’t work for anything after I move

Most Maryland police agencies have their dispatch talkgroups in the clear, but there are a few exceptions. Also be aware that the state police and most county police agencies are simulcast P25 Phase 1/2 systems - or will be shortly - which means a pretty expensive scanner or Unication paging receiver will be required for good quality reception.

 

[boatbod]

Most Maryland police agencies have their dispatch talkgroups in the clear, but there are a few exceptions. Also be aware that the state police and most county police agencies are simulcast P25 Phase 1/2 systems - or will be shortly - which means a pretty expensive scanner or Unication paging receiver will be required for good quality reception.

...or a cheap Raspberry Pi3 + RTL dongle and some significant patience to install op25

 

[Mr_Boh]

...or a cheap Raspberry Pi3 + RTL dongle and some significant patience to install op25

Not to hijack this thread too much, but do you have a good “starter guide” for deploying it?

 

[maus92]

Not to hijack this thread too much, but do you have a good “starter guide” for deploying it?

This is what is missing from the Raspberry Pi 3+ / OP25 / RTL solution - but Boatbod has made an excellent software installation routine, so I'll let him answer. Like most crowd-sourced software projects, the developers concentrate on the coding, and the documentation tends to be thin, confusing and outdated. What is needed is a concise, accurate, all-in-one-place procedural document.

I have a Raspberry Pi that runs on the FIRST system, and it does an outstanding job decoding audio. Its downside is that it is very technical solution - a lot of people have trouble programming the newer scanning receivers, and the Raspberry Pi solution is even more complex for the average / not particularly computer savvy listener.

As far as cost: Raspberry Pi ~$35; RTL/ant bundle, $25; OP25 free. You will need a keyboard, mouse and monitor to set it use and run, and a speaker or headphone. I used spare computer gear I have lying around, but others may not have access to it, so that would be and additional cost. Consumer scanners that reliably decode P25 simulcast cost $600+; Unications cost ~ $550.

 

[boatbod]

Not to hijack this thread too much, but do you have a good “starter guide” for deploying it?

As maus92 already said... not really... but there are resources you can google online and I hang out in the RR SDR forum and answer questions etc. I suggest you may wish to start here: https://forums.radioreference.com/threads/experiments-with-op25-and-liquidsoap.381446/

The op25+liquidsoap setup is most appropriate for a RPi3 as it yields best audio. If you are familiar with "git" and Linux, you can go a long way by doing the following:

cd ~
git clone https://github.com/boatbod/op25
cd ~/op25
./install.sh

After that, peruse the file ~/op25/README-rpi3-liquidsoap for hints on how to proceed further.

Tutorial on Setting up OP25 for P25 Phase 2 Digital Voice Decoding
OP25 For Dummies – Or how to build a police scanner for $30 (Part 1) | John’s Tech Blog

 

[DIGITALCLUELESS]

I'm glad to see software is being developed to defeat encryption.

 

[KB4MSZ]

I'm glad to see software is being developed to defeat encryption.

I used to have access to this. I should have never retired from Control.

 

[boatbod]

I'm glad to see software is being developed to defeat encryption.

^^^???

Op25 can identify when encryption is being used, but it makes no attempt to decrypt. While not technically hard to implement a decryption step in the datastream, doing so successfully would require knowing the keys and I very much doubt these are going to be handed over by the agencies that set them up.

What op25 does well is decode the IMBE/AMBE voice streams used by P25 radios. These streams are not necessarily encrypted, merely encoded. Big difference especially as far as legality is concerned.

 

[Bob1955]

Are all Maryland police agency radios channels encrypted? Or are there still scanners out there that will pick them up?

Baltimore County, MD is P-25 Digital. I'm not sure if it is Phase 1 or 2 at this time.

 

[maus92]

Baltimore County, MD is P-25 Digital. I'm not sure if it is Phase 1 or 2 at this time.

Phase 1.