New Motorola system?

[rangerfourever]

Just got told via email that our County is in negotiations with Motorola for a 9 site simulcast Astro 25 700/800 TDMA trunk system. Is this the newest M trunking tech? just curious....my contact says he does not think that any current digital scanner will be able to track this new system.

David White

[alex]

Just got told via email that our County is in negotiations with Motorola for a 9 site simulcast Astro 25 700/800 TDMA trunk system. Is this the newest M trunking tech? just curious....my contact says he does not think that any current digital scanner will be able to track this new system.

David White

Your contact sounds correct. The only thing the scanners support at this time is decoding of IMBE digital, anything new that comes out will have to get re-worked in to the scanners in order for them to receive.

[nmfire10]

The words "Astro 25" and "TDMA" together in the same sentence seems to indicate that somebody somewhere is confused.

[batdude]

APCO P25, Phase II



doug

[Wowbagger]

The words "Astro 25" and "TDMA" together in the same sentence seems to indicate that somebody somewhere is confused.

No, nobody is confused. Motorola submitted a proposal to APCO for a 2 slot TDMA extension to APCO-25, in order to meet the FCC 6.25kHz/conversation mandate that will be coming into effect in a few years. This was in competition to the Phase 2 CQPSK proposal APCO has already approved which allows an otherwise standard APCO-25 channel to occupy 6.25 kHz by changing the modulation type.

Motorola felt that a 2 slot TDMA system, using AMBE rather than IMBE to further reduce the data rate to one-half of standard APCO-25 would be easier to implement on the mobile units, as a linear final stage would not be needed as it would for the CQPSK proposal.

As of now, APCO has not ratified the Motorola proposal into the APCO standard, so Motorola will be releasing the standard as an extension to the APCO standard, with the extra trunking signaling blocks (TSBKs) being transmitted with a manufacturer's ID code of 0x90 (Motorola) rather than 0x00 (APCO standard).

(Personal opinion here!) I think that Motorola is hoping to present APCO with a fait accompli - they would get enough systems out there that APCO would relent and approve Motorola's submission.(/Personal opinion)

Of course, what scares me is that CQPSK and TDMA are not mutually exclusive: they could move the Motorola 2 slot TDMA system from C4FM to CQPSK and get 2 conversations in one 6.25kHz wide channel, for a 3.125kHz per call bandwidth - damn near as tight as SSB - and almost as intelligible.

[RKG]

Ahem. SSB, done correctly and with enough investment in equipment and operator skills, isn't unintelligible. I conduct ops weekly with units up and down the east coast on marine SSB, and the best of them sounds like over on the next mooring.

On the other hand, you couldn't begin to touch the degree of stability required to do this in typical public safety mobile and portable equipment, operated by folks who couldn't care less about radio.

[escomm]

No, nobody is confused. Motorola submitted a proposal to APCO for a 2 slot TDMA extension to APCO-25, in order to meet the FCC 6.25kHz/conversation mandate that will be coming into effect in a few years. This was in competition to the Phase 2 CQPSK proposal APCO has already approved which allows an otherwise standard APCO-25 channel to occupy 6.25 kHz by changing the modulation type.

There is no mandate by the FCC that requires anyone to move to 6.25Kc technology. There is a recommendation by the FCC that suggests manufacturers should leapfrog 12.5Kc and go to 6.25Kc, but the FCC recognizes that 6.25Kz technology is nowhere near primetime, and the FCC recognizes that requiring anyone to go to 6.25Kc before the technology is widespread will not happen.

[Wowbagger]

There is no mandate by the FCC that requires anyone to move to 6.25Kc technology.

YET.

As I said, it's a few years out.

[Wowbagger]

Ahem. SSB, done correctly and with enough investment in equipment and operator skills, isn't unintelligible.

Yes, I know - after all, I just spent an week doing nothing but SSB for Route 66 on the Air - and got MANY compliments on my audio. But then again, I'm using a rig that does SSB *right* (audio through a Hilbert filter, then through the quadrature modulator, then to IF, then to analog, then up to RF), rather than cheezing it by trying to filter off the unwanted sideband at the IF, and I understand that compression is like salt - a little makes it better, a lot just raises your blood pressure. I take the time to check my actual TX signal out to make sure I am sending a clean signal and no unwanted crap.

But having to deal with too many rigs that have an offset between RX and TX so that the operator tunes you in but sounds like Donald Duck or Barry White to you, rigs that are putting out something just short of AM, rigs that have so much compression that even properly tuned in, the other guy sounds like the adults on Peanuts (MWAAA-MWAAA-MWAA-MWA-MWAAAAA-QSL?).... Not fun at all.

[escomm]

There is no mandate by the FCC that requires anyone to move to 6.25Kc technology.

YET.

As I said, it's a few years out.

OK, fair enough, looking back though your comments appear to imply that the mandate has already been and that it is just a matter of time before it becomes effective. There is a mandate to go to 12.5Kc channel spacing that is in force, although my gut is that the transition date will be pushed back (again). I think we're looking at 2013 now??

[imho]With the way things are going at the FCC, I doubt a move to 6.25 will ever be forced until Motorola says OK. [/imho]

[rangerfourever]

So in essence what Doug said.... APCO 25 Phase II with maybe our County being one of Motorola's tests for their new system? The Motorola mothership is about 10 miles north of our County seat, so we do see "testing" by Motorola in the field. Funny thing is that our locals have jumped on the new State wide 700/800 super system put up by Motorola, ( I have a $7,800.00 XTL 5000 control station next to me as I type) with two primary simulcast sites in the center of our County. Got to love the interoperability?????

David

[nmfire10]

As of now, APCO has not ratified the Motorola proposal into the APCO standard, so Motorola will be releasing the standard as an extension to the APCO standard, with the extra trunking signaling blocks (TSBKs) being transmitted with a manufacturer's ID code of 0x90 (Motorola) rather than 0x00 (APCO standard).

So why are they calling it Astro-25 if it isn't Project 25?

[escomm]

As of now, APCO has not ratified the Motorola proposal into the APCO standard, so Motorola will be releasing the standard as an extension to the APCO standard, with the extra trunking signaling blocks (TSBKs) being transmitted with a manufacturer's ID code of 0x90 (Motorola) rather than 0x00 (APCO standard).

So why are they calling it Astro-25 if it isn't Project 25?

Same reason they called it Private Line when it wasn't Private?

[Wowbagger]

So why are they calling it Astro-25 if it isn't Project 25?

That's *why* they are calling "Astro-25", not "APCO-25".

They also called a Smartnet control channel with APCO-25 CAI signaling on the voice channel "Astro-25".

We are starting to get into dangerous (for me, anyway) territory here: I'm having to constantly check what I am allowed to talk about and what would violate my NDAs.

[nmfire10]

Ok, I'll say it for you. They are giving it a creative name to make it sounds like it is P25 but it really isn't. How's that?

[redbowl]

Like any system, there is the base standard and then there are the proprietary extension. ASTRO is MOTs marketing name that says it does all the standard things - and maybe more. In this case they are adding extensions (that are allowed by the spec) to create "future" functionality. Many of these extensions are already in proposals to APCO for inclusion but until then, MOT has to mark them as non-standard.

[rangerfourever]

Got a new email from my "inside" contact, who said that some members of the ETSB board that governs 911 monies in our county, are not pleased with going with an "unproven" (their words) technology. What in laymans terms does TDMA do for me, an officer in the field, that my Astro/SmartZone/APCO 25 radio can not do?

Thanks just trying to stay current

David

[libuff]

putting it VERY basically, as with MotoTRBO each channel can be divided into two time slots, thereby doubling the amount of traffic without collisions on the same channel.

i've heard some grumblings about a system in the NYC metro area with the same idea...

[redbowl]

As a user in the field, TDMA does nothing additional for you. As a system designer it does a couple things. First, it will require more advanced equipment to eaves drop because you have to align to the time slots. Second, it should help make the system cheaper since you can carry more then one conversation on a channel at a time (if the voice encoder is improved).

One way to improve the channel efficiency is to compress the data better so you don't send as many bits over the air. If the compression is four times better, then you can split your channel into a four slot TDMA system and have four conversations on one frequency simultaneously. Now you can buy 1/4th the number of base stations and only need 1/4th the number of frequencies to cover the same area with the same call capacity.

[mr.syntrx]

As a user in the field, TDMA does nothing additional for you.

Actually, it reduces transmitter and receiver duty cycle and therefore power consumption, a la AMPS vs GSM.

[Wowbagger]

It also can allow a single channel to serve as both voice and control channel (in different slots). This can help smaller sites as they can have fewer actual RF decks to support users - in the limiting case allowing very simple system to use one transmitter for 1 CC and 1 VC. That was one of the strengths of LTR for simple guys - a single channel base was possible, if all you needed was one conversation at a time.

[RFguy]

putting it VERY basically, as with MotoTRBO each channel can be divided into two time slots, thereby doubling the amount of traffic without collisions on the same channel

I believe that you can only aceive the 2 time slot funtion when operating with a MotoTrbo repeater.

MotoTrbo direct (simplex), only supports a single time slot. Please correct me if I am wrong. Thanks, Alan

[HumHead]

You are correct.

You cannot use the dual time slots in simplex, only through a repeater, which actually makes a fair amount of sense when you stop to think about synchronizing the timing between simplex portables that are not all within range of each other.