However, portability of this setup is limited as you have to have many pieces of equipment with you. As an example, DSDPlus will decode MotoTrbo as opposed to no standalone scanner being able to do so currently. Changing modulation types is often as easy as changing programs. There are some advantages like cost and being software based. It will take some time and patience to understand, research, and know the types of systems and system specifics.

This setup is much cleaner and the Unitrunker developer has implemented advanced features like drift correction. Previously, there needed to be a plug-in for both Unitrunker and SDRSharp, there were all kinds of “moving parts.” In one respect, being able to see the signal waveform on a spectrum analyzer made it much easier to fine tune the PPM correction on-the-fly as opposed to guessing on a modulation scope. This manly thanks to Rick, the developer of Unitrunker who implemented support for the RTL-SDR chipset in his program. This project is still very complicated but it is MUCH easier than it used to be. I will cover a two dongle setup and do not plan to cover a single dongle setup. You will miss calls because that notification comes across the control channel while the dongle was tuned to a voice transmission. Theoretically, the single dongle listens to the system control channel and then tunes to voice calls, then back to the control channel.

You can do the project with one dongle but you loose many features in Unitrunker like talkgroup priority. I already had a premium Radio Reference account. You will need at least two RTL-SDR dongles ($20/each) and a copy of Virtual Audio Cable ($26). I had played around with these dongles and read about the many projects people were doing with them. Lurking around the Radio Reference forums, I saw references to being able to use the RTL-SDR dongles for trunked digital decoding. Ironically they will “go digital” but move to 700/800 MHz.Īs a casual listener, I wasn’t exactly thrilled with spending at least $500 for a scanner capable of digital ( P25 mostly) and trunked system tracking (also Radio Reference wiki). To get more use out of the radio spectrum, the FCC decreed a narrowbanding mandate requiring a “maximum of 12.5 kHz bandwidth across the private land mobile bands between 150-174 and 421-512 MHz.” This means going digital for much of that radio spectrum because traditional FM transmissions are 15 KHz. In college it was great to listen in on a party weekend hearing fights, disturbances, or why my street suddenly filled with cars at 3 AM. I have been a casual scanner listener for years and like to listen to emergency calls nearby. The project that got me really into experimenting with the RTL-SDR dongles is using them to decode P25 digital trunked public service radio systems.

Decrypt P25