Welcome back to Sarah from the SignalsEverywhere YouTube channel who has recently returned to producing videos from a hiatus. In her latest video, Sarah shows off her new OP25 Mobile Control Head Android App which allows you to implement a full P25 digital radio scanner at a fraction of the cost of a commercial digital scanner. In the past, Sarah had released a similar application written for the Raspberry Pi but has decided to shift her focus to writing an equivalent Android app that is less clunky and can be deployed for a lower cost. 

The app controls and displays information from the OP25 software that runs on a Raspberry Pi with RTL-SDR connected. It works by using a server application on the Raspberry Pi that manipulates the OP25 instance and its configuration files.

Sarah writes:

The application is a wrapper for OP25 that uses a raspberry pi and an android device to provide users with a mobile control head for their OP25 P25 scanner setup. Currently it's just a basic application but I'll be adding features like automatic site switching, etc.

OP25MCH: https://github.com/SarahRoseLives/OP25MCH

There is also a separate application I call the OP25Display which is just a display for a users existing OP25 instance.

OP25Display: https://github.com/SarahRoseLives/op25display

I am not going to lie, it doesn't sound the best.  There was no information for coder's to work off of, so what we have is rather crude, but intelligible.

If you are looking to help improve it, start here.  This is from the folks from the community that brought us what we have today.


There was also this tip from user "groovy"

If anybody wants to continue the research / work, I suggest you look at the osmocom GMR code that Sylvain Munaut worked on. Those phones use a similar codec - I believe with longer frames for the satellite latency. Initially he used the mbelib code, enhanced it for things like tone support, but he later rewrote the synthesis code completely. See OsmocomGMR for his presentations and source code.

Unless other developers take this on, DVSI releases specs, or you switch to a hardware-based decoder like the thumbDV, I don't see the dstar voice quality improving in the short term.

I'd love to see further work on OP25. More so on the transmit part (hooked to analog radio, perhaps using the MMDVM hardware/Arduino.   Anyone care to join forces with Max?

Perhaps an update to Johnathan Naylor's (2009) GUI Linux client that would decode and generate GMSK using a soundcard and interface to a radio with a 9600 Baud packet connector. ..

Wouldn't mind a way to hook op25 to Allstar either  :-)