Project 25 (P25)

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Project 25 (P25)
P25.jpg
Frequencies 136 MHzMegaHertz (MHz) 10^6 Hz136,000,000 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).
136,000 kHzKiloHertz (kHz) 10^3 Hz
,174 MHzMegaHertz (MHz) 10^6 Hz174,000,000 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).
174,000 kHzKiloHertz (kHz) 10^3 Hz
,860 MHzMegaHertz (MHz) 10^6 Hz860,000,000 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).
860,000 kHzKiloHertz (kHz) 10^3 Hz
,500 MHzMegaHertz (MHz) 10^6 Hz500,000,000 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).
500,000 kHzKiloHertz (kHz) 10^3 Hz
136,000 kHzKiloHertz (kHz) 10^3 Hz
136 MHzMegaHertz (MHz) 10^6 Hz
860,000 kHzKiloHertz (kHz) 10^3 Hz
860 MHzMegaHertz (MHz) 10^6 Hz
Frequency Range 136 MHzMegaHertz (MHz) 10^6 Hz136,000,000 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).
136,000 kHzKiloHertz (kHz) 10^3 Hz
- 860 MHzMegaHertz (MHz) 10^6 Hz860,000,000 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).
860,000 kHzKiloHertz (kHz) 10^3 Hz
Mode NFMNarrowband Frequency Modulation
Modulation PSKPhase-Shift Keying,C4FMContinuous 4-Level Frequency Modulation
ACFAutoCorrelation Function
Bandwidth 12500 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz).12.5 kHzKiloHertz (kHz) 10^3 Hz
0.0125 MHzMegaHertz (MHz) 10^6 Hz
12.5 kHzKiloHertz (kHz) 10^3 Hz
0.0125 MHzMegaHertz (MHz) 10^6 Hz
12.5 kHzKiloHertz (kHz) 10^3 Hz
0.0125 MHzMegaHertz (MHz) 10^6 Hz
Location Worldwide
Short Description Project 25 (P25 or APCO-25) is a trunked radio standard developed by The Association of Public Safety Communications Officials International (APCO-25) for use with public safety organizations around the world.
I/Q Raw Recording Download file
Audio Sample
Project 25 (P25 or APCO-25) is a trunked radio standard developed by The Association of Public Safety Communications Officials International (APCO-25) for use with public safety organizations around the world. P25 supports encrypted voice.


Phase I FDMAFrequency Division Multiple Access[edit]

Phase 1 radios use Continuous 4 level FMFrequency Modulation (C4FMContinuous 4-Level Frequency Modulation) modulation—a special type of 4FSK4-Level Frequency Shift Keying modulation—for digital transmissions at 4800 baudBaud (unit symbol Bd) is the unit for symbol rate or modulation rate in symbols per second. and 2 bits per symbol, yielding 9600 bits per second total channel throughput.

Phase I FDMAFrequency Division Multiple Access consists of C4FMContinuous 4-Level Frequency Modulation modulated signal or a CQPSKContinuous Quadrature Phase-Shift Keying modulated signal. Both fit in a 12.5 kHzKiloHertz (kHz) 10^3 Hz channel. Subscriber equipment transmit in C4FMContinuous 4-Level Frequency Modulation. Site equipment may transmit in C4FMContinuous 4-Level Frequency Modulation or CQPSKContinuous Quadrature Phase-Shift Keying. Simulcast uses CQPSKContinuous Quadrature Phase-Shift Keying modulation, however older Motorola ASTRO equipment used C4FMContinuous 4-Level Frequency Modulation simulcast in a special mode called "WIDE pulse" which is not P25 compliant. P25 CQPSKContinuous Quadrature Phase-Shift Keying Linear Simulcast Modulation is P25 compliant and is referred to as LSM. LSM is defined in the P25 standards

Phase II TDMATime Division Multiple Access[edit]

The Phase II standard is a 2-slot TDMATime Division Multiple Access signal that fits inside a 12.5 kHzKiloHertz (kHz) 10^3 Hz wide channel. Fixed site output modulation is H-DQPSKDifferential Quadrature Phase-Shift Keying with subscriber units using H-CPM on the input. This allows existing 12.5 kHzKiloHertz (kHz) 10^3 Hz wide license holders to double call capacity by upgrading their infrastructure to Phase II. The Phase II standard was approved in November 2010, and as of August 2011 Motorola has begun shipping Phase II systems.

Motorola ASTRO 25 systems can also have an optional feature known as Dynamic Dual Mode (DDM), which will seamlessly revert a talkgroup to FDMAFrequency Division Multiple Access operating mode if a Phase I only capable radio affiliates with a Phase II capable talkgroup.

Audio Samples[edit]

P25 Phase 1
Trunking Control Channel Encrypted Voice Channel

P25.jpg

P25 Voice.jpg

P25 Phase 2

Trunking Control Channel

Phase2 screen.png

Additional Samples[edit]

P25 Phase 1 Encrypted Voice Bursts:

Frequencies[edit]

Usually around ~860 MHzMegaHertz (MHz) 10^6 Hz or ~500 MHzMegaHertz (MHz) 10^6 Hz.

IQ Samples[edit]

Decoding Tutorials[edit]

Decoding Software[edit]

Hobby Level Software

Video Examples[edit]

Additional Links[edit]

Additional Images[edit]