Whats the difference

[greeneyes965]

Between all these? APCO-25, ASTRO, and Digital Trunking Discussion Discussion of Digital, CAI, IMBE, APCO-25, VSELP, AEGIS, and ProVoice Digital Modulation systems and technologies

Please someone tell me here in champaign county illinois were using Astro

[rdale]

Lots of answers for your first question in the Wiki. For Champaign Co, click on "DATABASE" at the top and find your county.

[greeneyes965]

I know i already seen that it didnt help at all

[rdale]

http://www.radioreference.com/apps/db/?ctid=600

Champaign County METCAD MDICE - 800 MHz
Project 25 Standard

"Project 25 Standard" means it is standard digital, usable with any newer digital scanner.

[greeneyes965]

So MDICE is ASTRO?

[rdale]

ASTRO 25 - using Google for "MDICE" gives me http://www.metcad911.org/MDICE/MDICE.htm

[greeneyes965]

So what is p25




Radios-800MHz mobile 2 uhf sp5450s and a vhf sp140
Scanners-bcd396t-2 pro 35 -pro 79-pro 92

[Grog]

Originally Posted by greeneyes965

So what is p25

Come on, do you have to be spoon fed everything? There is the RR wiki, there is google, use them instead of cross-posting the hell out of the forums.

Originally Posted by greeneyes965

Radios-800MHz mobile 2 uhf sp5450s and a vhf sp140
Scanners-bcd396t-2 pro 35 -pro 79-pro 92

Put that crap in your sig so those of us who have sigs turned off don't have to see what you have.

[N_Jay]

Originally Posted by greeneyes965

So what is p25




Radios-800MHz mobile 2 uhf sp5450s and a vhf sp140
Scanners-bcd396t-2 pro 35 -pro 79-pro 92

Write a question that shows what you know and asks for exactly what you don't so it can be answered.

As in:
I understand A, B, C, and think I get D, but I am confused by E.

You Sig is set in the "UserCP", and that is where your radio information goes. Not in the body of the post.

[greeneyes965]

People you dont have to be rude,ok

[greeneyes965]

Why are people rude on here?

[HarrisonRHW]

People aren't rude.. it just takes a lot of unnecessary space up on the forum to ask questions, which would be easy to find on the wiki here, if not a google search, and to most people it looks like you didn't take time to understand forum rules, or even how it works with things like signatures. It is okay to be new, but just take the time to understand available resources and how the forum works. In terms of asking questions, posting a new thread on the forum should basically be a last resort.

Originally Posted by N_J_H

Write a question that shows what you know and asks for exactly what you don't so it can be answered.

As in:
I understand A, B, C, and think I get D, but I am confused by E.

Do just that... forums aren't intended to rewrite the dictionary, if you need to know the specific difference between, say, Motorola Astro and Motorola Astro-25, then this is the place, but even that can be found without having to post a topic.

For starters though, Project 25 is a set of guidelines made by APCO (Association of Public Safety Communications Officials), and doesn't simply define a technology, it is a whole spectrum of guidelines for building a system. Here is some info: http://www.apco911.org/frequency/pro...formation.html

Go from there, and ask if you are confused about specific technologies as you look them on here on the Wiki or on Google.

[greeneyes965]

ok,sorry

[N_Jay]

Originally Posted by greeneyes965

People you dont have to be rude,ok

Not being rude, just trying to get to the question in a way that can be answered.

We don't know what you do know and what you don't so a general question is very hard to answer.

[N_Jay]

Originally Posted by HarrisonRHW

. . . . .
Do just that... forums aren't intended to rewrite the dictionary, if you need to know the specific difference between, say, Motorola Astro and Motorola Astro-25, then this is the place, but even that can be found without having to post a topic. . . . .

Not saying to "rewrite the dictionary", but it much easier to answer a question when you know the starting point and the bounds.

[chet1]

People in Champaign county Illinois may have a uniqe problem in regards to the signal. The signal is all of the things described above but the MDICE is unique in some way. I bought a new PSR 600 and it wouldn't receive the signal. Gre said it was a CQPSK simulcast signal and difficult to decode. They asked for the return of the radio, bench tested it and said it tested good; sent me a new one and it won't intercept the talkgroups either. Both pick up state police which has the same system description. My pro 96 has no problems. I live about 3 miles from a tower. Took the radio to within a block of another tower and still couldn't decode the signals.

[gabbott]

Originally Posted by chet1

People in Champaign county Illinois may have a uniqe problem in regards to the signal. The signal is all of the things described above but the MDICE is unique in some way. I bought a new PSR 600 and it wouldn't receive the signal. Gre said it was a CQPSK simulcast signal and difficult to decode. They asked for the return of the radio, bench tested it and said it tested good; sent me a new one and it won't intercept the talkgroups either. Both pick up state police which has the same system description. My pro 96 has no problems. I live about 3 miles from a tower. Took the radio to within a block of another tower and still couldn't decode the signals.

From reading the GRE web site, it didn't look like the PSR500/600 would do Astro, but if you're hearing ISP, then I must have missed something. Did you try taking the antenna off when you went to within a block of the tower? I saw another post that mentioned the receivers in the GRE's are very hot, so I'm wondering if the simulcast is overloading the front end.

Compatible Differential Offset Quadrature Phase Shift Keying, more commonly known as CQPSK (don't ask me why) is the basis for the Astro25 vocoder. The front end of the typical scanner is not all that selective, so in a simulcast system, such as MDICE, the CQPSK signal can be badly distorted and cause the radio to miss transmissions. I read post after post about the Uniden models missing less traffic than the Pro96 and I think this may be an indicator of the quality of the receivers used. If a user is closer to one of the simulcast tower sites, the chance of decoding the signal is greatly improved. Where a user will suffer the most is if they are located between towers and the radio 'sees' more than one signal at a time, leading to the inability to decode a clean signal.

StarCom21 in East Central Illinois is an Intelligent Repeat (IR) system, not simulcast, so the transmission should sound cleaner. The down side to IR for scanners being that unless a radio is set to the desired talk group you wish to monitor and is affiliated with a tower within your range, you will not hear the desired talk group transmissions. All transmissions are broadcast from all towers in a simulcast system, such as MDICE.

[rdale]

Originally Posted by gabbott

From reading the GRE web site, it didn't look like the PSR500/600 would do Astro

They certainly do... I think you mean "P25".

Compatible Differential Offset Quadrature Phase Shift Keying, more commonly known as CQPSK (don't ask me why) is the basis for the Astro25 vocoder.

No. C4FM is what most P25 systems use. CQPSK is used for simulcast towers. Both are P25 / Astro25.

[N_Jay]

Originally Posted by gabbott

Compatible Differential Offset Quadrature Phase Shift Keying, more commonly known as CQPSK (don't ask me why) is the basis for the Astro25 vocoder. The front end of the typical scanner is not all that selective, so in a simulcast system, such as MDICE, the CQPSK signal can be badly distorted and cause the radio to miss transmissions.

CQPSK and C4FM are a linear and non-linear set of compatible digital modulation waveforms. That means a PROPERLY designed receiver can receive either. And FM (FSK) (Discriminator based) receiver will only receive C4FM well.

Some simulcast systems used a proprietary form of modulation that Motorola called LSM (Linear Simulcast Modulation). This would be received properly by "most" proper CQPSK receivers but not all, and would be even worse on a FM/FSK receiver.

This is NOTHING to do with the vocoder, and NOTHING to do with selectivity.

Simulcast also adds phase/timing noise to the received signal that some receivers are better then others at ignoring/removing.

I don't know if MDICE is LSM or not, but would guess it is.

[chet1]

Thanks for the answers on the psr 600. It gives me some ideas to try. I am receiving a chopped word here and there; and in some cases 2 or 3 or 4 words together. But side by side with the pro 96 it doesn't pick up any signal at all 95% of the time for the Rantoul PD.