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Difference Between Apco P-25 Phase 1 And Phase 2

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fireant

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Can anyone explain to me what the difference is in phase 1 and phase 2 on a P-25 system?

thanks

fireant
 

mam1081

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I'm pretty sure Phase II P25 will all be 6.25 kHz bandwidth. I'm not sure, but I think it's supposed to be TDMA on trunked systems. The Phase I stuff is 12.5 kHz [C4FM], but can be 6.25 kHz [CQPSK], both in FDMA modulation.

Supposedly Phase II will require all new equipment. I don't know how true that is - seems like a lot of money for those big cities to go "Phase II". Phase III is supposed to follow II more quickly than II follows I. I think Phase III is to better integrate internet and data into the radios (probably will be all TDMA).

Maybe that helped?!:confused:
 
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N_Jay

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mam1081 said:
I'm pretty sure Phase II P25 will all be 6.25 kHz bandwidth. I'm not sure, but I think it's supposed to be TDMA on trunked systems. The Phase I stuff is 12.5 kHz [C4FM], but can be 6.25 kHz [CQPSK], both in FDMA modulation.

Supposedly Phase II will require all new equipment. I don't know how true that is - seems like a lot of money for those big cities to go "Phase II". Phase III is supposed to follow II more quickly than II follows I. I think Phase III is to better integrate internet and data into the radios (probably will be all TDMA).

Maybe that helped?!:confused:
First, there is no Phase 3.

Phase 1 was everything completed in 1995, Phase 2 became the name for everything else.
This has caused much confusion.

Most refer to Phase 1 as the current Common Air Interface, 9600 bps, FDMA C4FM/CQPSK.
Most refer to Phase 2 as the upcoming (yet to be nailed down) TDMA scheme.
TDMA will be 2:1 TDMA (initially) on trunked systems.

ISSI, and other interface specifications are also often included in Phase 2.

The important thing to remember is that the whole body of individual specifications, whether they are in "Phase 1", Revisions of "Phase 1" documents, or in "Phase 2"; are all parts of a suite of standards that can be used in many configurations to build equipment and systems.

As for whether the TDMA scheme requires "all new equipment" will depend on a lot of things.
1) How the standard is finally decided
2) How the manufacturers decide to implement the finally decided standard
3) what equipment you have from those manufacturers.

There are provisions in the TDMA standards (Phase 2) to allow for FDMA (Phase 1) equipment backwards compatibility.
 
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N_Jay

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Sipho said:
So, what's the real story on APCO-25?

go to the following address http://www.info4u.us/APCO25/
and there is an interesting article that will answer a lot of your questions.
Careful.:roll:
That page has a lot of "facts" with some "opinions" and some "just plain errors" scattered through. Not only are they mixed, but the opinions are stated as facts, and they are often based on the "errors"!:evil: :roll: :evil:

It is a sales piece to help a land mobile dealer to sell what he has.
 

n4voxgill

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That is the worst site I have ever seen. This guy has never heard of re-farming, much less that it is independent of APCO 25. I guess he never heard of NTIA either. He doesn't even know that FEMA is a part of DHS. Hell, he doesn't even understand what APCO is and that they have no standard setting authority.
 

Sipho

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Sorry, Thanks for bringing it to light. I'm searching trying to make sense of this stuff and came across this article. I did notice the fact that it was a dealer and I did have my doubts as like you say they will say anything to make a sale. Maybe someone else who comes across this site will wise up after your comments. So I'm still trying to make sense of things.
 
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N_Jay

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Ask clear questions, get clear answers (up to the clarity of the naturally confusing situation).:D :wink:
 

denseglow

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OK, I am confused. 6.25 would be like 800.99375 and 12.5 would be like 800.9875? what else is there?
 

studgeman

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When TIA, the actual standards body which approves this stuff, figures out what the next over the air scheme looks like, we'll let you know. There are several proposals out there, most of them having some sort of TDMA scheme. The three to pay attention to are EADS, which I am not to familiar with their proposal, Motorola, kinda resembles an early iDEN with a new Vocoder, and M/A Com, which strangely enough resembles OpenSky. And before someone takes an issue with what I just said, notice I used the word RESEMBLES, which is not intended to mean SAME, but just intended to give a description of the PROPOSED technology. When TIA actually approves something, then we will know what "Phase II" really is, untill then we are left with opinion, speculation, just hopefully no more plain errors <grin> btw can we finish what is commonly known as "phase I ?" Just a thought....
 
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N_Jay

Guest
studgeman said:
When TIA, the actual standards body which approves this stuff, figures out what the next over the air scheme looks like, we'll let you know. There are several proposals out there, most of them having some sort of TDMA scheme. The three to pay attention to are EADS, which I am not to familiar with their proposal, Motorola, kinda resembles an early iDEN with a new Vocoder, and M/A Com, which strangely enough resembles OpenSky. And before someone takes an issue with what I just said, notice I used the word RESEMBLES, which is not intended to mean SAME, but just intended to give a description of the PROPOSED technology. When TIA actually approves something, then we will know what "Phase II" really is, untill then we are left with opinion, speculation, just hopefully no more plain errors <grin> btw can we finish what is commonly known as "phase I ?" Just a thought....
Both EADS and Motorola want 2 slot at 12.5 KHz.

Well the big difference is EADS would like to see 12 KBPS on voice channels using the current codec, while Motorola would like to see 9600 BPS (current modulation) using a new codec.

Neither resembles iDEN any more than any other TDMA scheme does.

M/A-COM was late to teh game and wants 4 slot at 25 KHz. (How much this resembles OpenSky is open for debate)

The two to watch in the first round are EADS and Motorola. It is a shame that M/A-COM did not bring in OpenSky earlier.

In the second round, M/A-COM could have a shot. (Just my opinion)

In reality, the standards are a consensus process, so what comes out will most likely have some input from all.
 
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N_Jay

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denseglow said:
right, but I am just asking, is those correct examples of the 6.25 and all that?

No.

You are assuming the a certain center frequency defines a certain bandwidth , and that is incorrect.
 
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