This APCO P25 Decoder software makes it possible to receive and listen to digital APCO P25 channels on WiNRADiO WR-G305 Series receivers.

 (Will not follow a trunked system. Can determine the type of received channel and decode voice channels, but it does not actually follow the trunked channels by decoding the control channel)

APCO Project 25 (P25) was developed by joint efforts of the Association of Public Safety Communications Officials International (APCO), the National Association of State Telecommunications Directors (NASTD), several US Federal Agencies and the National Communications System (NCS). It was established to address the need for common digital public safety radio communications standards for public safety, homeland security and emergency response.

APCO P25 digital communications offer numerous advantages over analog ones, such as much clearer received audio, separation of services (fire, homeland security, maintenance, etc.) into coded "talkgroups", individual radio identification numbering and tracking, GPS location, digital messaging, etc.

For this project, WiNRADiO licensed the IMBE (Improved Multi Band Excitation) vocoder from Digital Voice Systems, Inc. (DVSI) and combined it with WiNRADiO proprietary software to provide a complete P25 demodulator/decoder as a simple to use, low-cost software add-on for WR-G305e or WR-G305i users.
 

The APCO P25 Decoder, upon installation, can be selected from the receiver's Demodulators top bar menu, as simply another alternative demodulator. The APCO P25 Decoder then appears fully integrated within the receiver front panel:

The APCO P25 Decoder panel consists of the following main parts:

 Spectrum scope, which shows the real-time spectrum of the received signal
 Notch filter, which makes it possible to eliminate or reduce effects of interference
 Analyzer panel, which shows the type of received signal and its parameters
 Squelch panel, which makes it possible to restrict reception to particular P25 users or groups
 Recorder/player, which can record audio as well as the intermediate frequency signal
 Play list, which makes it possible to easily and quickly select previously recorded files

APCO P25 Analyzer Panel

The APCO P25 Analyzer panel makes it possible to determine whether the incoming signal is APCO and analyze its parameters. There is also an automatic switching facility which makes it possible for the receiver to stay tuned on a mixed analog/digital channel and the switching between standard FM demodulation and APCO P25 digital decoding is performed automatically. The Analyzer will also determine the type of received digital signal (voice, data or trunking control channel), whether any encryption is being used and what type of encryption it is. (However, it will not actually decode encrypted signals.) The signal BER (Bit Error Rate) is also measured and displayed, making it possible to assess the quality of the received signal.

APCO P25 Digital Squelch Panel

The APCO P25 Digital Squelch panel makes it possible to set the numerous digital parameters available in an APCO P25 transmission to filter out unwanted transmissions and target only one particular user or a user group. This is accomplished using APCO P25 specific digital codes, such as the NAC (Network Access Code), SID (System Identification), TGID (Talk Group Identification), etc. The digital squelch can also control the recorder, so that only the desired communication of a particular talkgroup or individual user is being recorded. In addition to decoded audio, the built-in recorder can also record the incoming signal in its raw, undecoded form at the IF (intermediate frequency) level. This makes it possible to "re-receive" the transmission many times over with changed parameters (for example different notch filter settings and/or digital squelch), archive unknown transmissions for later analysis and decoding, etc.

Minimum system requirements

 IBM PC AT compatible, 500MHz Pentium CPU, 64MB RAM, 10MB free HDD space
 Windows 98/2000/XP
 16-bit SoundBlaster compatible* sound card
 WiNRADiO WR-G305e or WR-G305i receiver

* Sound card must support full-duplex at 48 kHz sampling rate, without AGC (recommended model Sound Blaster Live! or similar).