My Rainy Day Project

Joined
Sep 26, 2004
Messages
10
Location
Natchitoches, LA
#1
Using a Raspberry Pi 3, an RTLSDR V3 Dongle, a small OLED display, and the OP25 software I built a tiny P25 scanner for LWIN today. It's currently scanning the Natchitoches site. Image of display is attached. So, what will be today's project!

--Ron, KA5LUG
 

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Joined
Dec 19, 2009
Messages
215
Location
Michigan
#3
Wow great job!

I have been thinking of trying this sort of thing for a while now. I don't have a RasPi at this time, maybe I should pick one up.

How well does it decode the audio?

Do you think more than one dongle could run on this setup?

My goal is to duplicate the functionality I have with my home setup in a small package. I am running three RTL-SDR dongles, Unitrunker, DSD+ with virtual cables on a Dell Core i5 laptop which allows me to monitor two active talk groups at once, left and right audio channels. I don't think that the RasPi and most other SBCs have the horsepower to run the setup i described above. I am hoping that OP25 is much more efficient in handling radio duties and decoding P25 audio and would be able to run three radios and decode the audio for two channels. I might be asking for too much from current inexpensive SBC platforms.
 
Joined
Sep 26, 2004
Messages
10
Location
Natchitoches, LA
#5
Not that I have seen but just for kicks I did get it to run on a PI zero last night. The zero does not have the built-in audio out so that means you would also need a USB sound device as well.
 
Joined
Sep 26, 2004
Messages
10
Location
Natchitoches, LA
#6
It decoded actually much better than expected. Overall quality is very good. I just started playing with OP25. It will handle multiple P25 systems but it appears that all of the control channels would need to be within the bandwidth supported by the SDR. They do have a multi_rx script to support more than one device, but currently, it doesn't appear to cover trunking. For the price - It's pretty impressive and a lot of fun to play with. I'm only seeing about 30% CPU usage on average. Less when just sitting on the control channel.

--Ron


Wow great job!

I have been thinking of trying this sort of thing for a while now. I don't have a RasPi at this time, maybe I should pick one up.

How well does it decode the audio?

Do you think more than one dongle could run on this setup?

My goal is to duplicate the functionality I have with my home setup in a small package. I am running three RTL-SDR dongles, Unitrunker, DSD+ with virtual cables on a Dell Core i5 laptop which allows me to monitor two active talk groups at once, left and right audio channels. I don't think that the RasPi and most other SBCs have the horsepower to run the setup i described above. I am hoping that OP25 is much more efficient in handling radio duties and decoding P25 audio and would be able to run three radios and decode the audio for two channels. I might be asking for too much from current inexpensive SBC platforms.
 
Joined
Sep 26, 2004
Messages
10
Location
Natchitoches, LA
#7
Below are the links to several sites I used to compile information.

Advancing Ham Radio.. different ideas: Listening to local 700 MHz Simulcast public safety cheaply
This is the article that got me interested.

Update on P25 scanner — new version, and new installation instructions | John's Geekblog
Following this I was able to download the source, compile and get most of a working config for my setup.

https://learn.adafruit.com/adafruit-pioled-128x32-mini-oled-for-raspberry-pi
(I used a generic I had laying around that I had purchased online for about $5. I used the available adafruit libraries and examples to add the necessary pieces to the OP25 terminal.py script.

When working with the .TSV config files I suggest using a spreadsheet to build and edit. I lost at least an hour before I figured out the Nano editor was not embedding tabs but rather spaces which caused errors and aborts.

Having at least an intermediate level of understanding with LINUX/Raspbian at the command-line and Python will make things much more enjoyable. :)

-Ron


Very neat !!... Care to explain how you did it ?
 
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Joined
Sep 26, 2004
Messages
10
Location
Natchitoches, LA
#8
I think I am going to look for one of the old Radio Shack Weather Cubes to house the pieces! Should make for a small package with a cool retro look. I can remember always wanting one of those as a kid. Time to search ebay!
 

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Joined
Jun 16, 2013
Messages
3,201
Location
Texas
#11
I think I am going to look for one of the old Radio Shack Weather Cubes to house the pieces! Should make for a small package with a cool retro look. I can remember always wanting one of those as a kid. Time to search ebay!
I have some vintage Moto speakers laying around...that's what I'd use if I could bring myself to cut them up.
 
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