scannerprogrammingofLvKs
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With any scanner that can be programed for a phase 2 system, why is there not a phase 2 system to choose from with in the radio ( TSYS / NEW ) ? it only shows P25 Auto or P 25
Phase 2 Programing System
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The scanner can figure out if the talk group is TDMA (Phase 2) or FDMA (Phase 1) automatically. There is no need to call out if the system is P1 or P2 in programming.
Plus, for 99% of the systems out there, Phase 1 or Phase 2 is talk group based and not control channel or system based, so there is no need to add that extra info into the talk group programming.
The scanner is smart enough to know what the TG is based on the overhead messages.
Plus, for 99% of the systems out there, Phase 1 or Phase 2 is talk group based and not control channel or system based, so there is no need to add that extra info into the talk group programming.
The scanner is smart enough to know what the TG is based on the overhead messages.
scannerprogrammingofLvKs
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Thank you for the info.
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Phase 2 P25 is trunking and follows the control channel data stream to use either Phase 1 or Phase 2 as determined by the system administrator.
ka3aaa
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the difference between phase 1 and phase 2 is the amount of audio spectrum used, phase 1 audio is 25 khz wide and phase 2 is 12.5 khz wide.
There are some very rare Moto phase 1 systems out there that are 25 kHz channels from what I understand, but they may not even exist anymore (X1?). Phase 1 and phase 2 are both 12.5 kHz channels in all other systems. The occupied bandwidth varies between manufacturers and their various pulse shaping filters, but they fit well within the part 90 masks for 12.5 kHz channels. There can be two interleaved voice streams inside a single phase 2 channel (why it is called time division multiple access / TDMA). The synthesized audio has a sample rate of 8 kHz. Typically, phase 2 is part of a turnked system where the control channel is phase 1. There are also a few new systems where the control channel is phase 2. They have been referred to as TDMA CC here on the forums.
Nope. Both FDMA and TDMA fit within a 12.5 kHz wide channel. Aside from what @btt already posted explaining some of the technical details of P25, your post doesn't make any sense solely based on the fact that the narrowband mandate implemented nearly a decade ago requires emissions in the VHF and UHF bands to be no more than 12.5 kHz wide, so how exactly would P25 Phase I FDMA be 25 kHz wide?
slicerwizard
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Yeah, nah.
chrismol1
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Is that what this is? while on topic of the last few posts, the digital modulator type in motorola CPS. Options are C4FM, CQPSK and WIDE, what is WIDE and when was that used? Any history on it? Pre-narrowband digital as described I'm assuming?
CPS help files list as
"Digital Modulator Type ASTRO
WIDE: Wideband simulcast operation. Available When: When the Tx Deviation field is not set to "2.5 kHz"."
CPS help files list as
"Digital Modulator Type ASTRO
WIDE: Wideband simulcast operation. Available When: When the Tx Deviation field is not set to "2.5 kHz"."
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Actually I believe it is RADIO based. You can mix different types of radios on a single TG.
P25 Phase 2 TG are set in 6.25khz talk paths. While FDMA Phase 1 TG are set in 12.5khz talk paths.
So if you have 5 voice channels on a system, 1 is dedicated to the Control Channel and 4 are talk paths. (assuming your not running data on it).
Each of these is 12.5khz wide. So Phase 1 is 12.5 or Phase 2 are each 6.25khz wide and you can run both simultaneous.
If you have Phase 1 your limited to 4 talk paths, but if you are running in Phase 2 you can have 8 talk paths. In Phase 2 each frequency will have Slot 0 and Slot 1.
So if you have 5 voice channels on a system, 1 is dedicated to the Control Channel and 4 are talk paths. (assuming your not running data on it).
Each of these is 12.5khz wide. So Phase 1 is 12.5 or Phase 2 are each 6.25khz wide and you can run both simultaneous.
If you have Phase 1 your limited to 4 talk paths, but if you are running in Phase 2 you can have 8 talk paths. In Phase 2 each frequency will have Slot 0 and Slot 1.
This is also incorrect. Phase II talkgroups are not 6.25 kHz wide. In fact a TDMA traffic channel uses most of the 12.5 kHz channel width, even if only one slot is active. Remember, this is TDMA, which is TIME Division Multiple Access. The talkpaths alternate in 30ms slots, they don't exist side by side in 6.25 kHz wide talkpaths.
P25 Phase II is "6.25 equivalent" for the purpose of measuring spectrum efficiency, that's all.
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Being that guy again, it's 30ms TS. And what's really cool is every 9th TS cycle the subscriber looks back at the repeater output to see if it's still there and for any updates/instructions.
Carry on...
Oh yeah, iDEN uses 45ms TS in case anyone cares.
Sucks getting old.
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