Phase 1 / Phase 2

[retiredmich]

I have been reading a lot of different post about Phase 1 & Phase 2 for scanners, I am not a real genus for scanners, But what is the different between the Phase 1 & Phase 2 scanners ? Thanks in advanced.

 

[n5ims]

Phase 1 is the old single channel per frequency P-25 technology. Phase 2 is the new multiple (generally 2) channels per frequency P-25 technology (there are multiple timeslots on each frequency that provide the multiple channels). A Phase-2 scanner will work on Phase-1 signals, but a Phase-1 (only) scanner will not pick up the new Phase-2 signals.

 

[N2ICV]

Look up P-25 and learn!...like this https://en.wikipedia.org/wiki/Project_25 or http://wiki.radioreference.com/index.php/Project_25

 

[Spitfire8520]

P25 Phase I uses what is known as Frequency Division Multiple Access (FDMA) to divide up voice/data for the users. This means that it divides the frequencies for a single use (frequency division).

P25 Phase II uses Time Division Multiple Access (TDMA). In P25 Phase II, each frequency has 2 time slots which can each be dedicated for a single use. You can think if it as spending half it's time sending information on one talkgroup and the other half sending information of another talkgroup if you would like (time division).

A large part of Phase II's appeal is that you can effectively double the amount voice traffic carried per frequency. This achieves the FCC desired 700 MHz narrowband (6.25 kHz) efficiency that they attempted to mandate. The FCC has since lifted narrowband requirements for 700 MHz.

The image below has a visual representation of this, you can think of Analog as P25 Phase I and TDMA as P25 Phase II. If you would like, I could take some time to create a more P25 specific example.

 

[retiredmich]

WOW !! , Thanks for all the info on the Phase 1 & 2, never thought it was all that & more, Thanks again every one.