Quantar P25 voting mix mode

[cjrd1993]

Ok...this may have been discussed over and over...but here it goes:

I have a analog system that uses an MTR2000 repeater (configured as a base station) controlled via 4 wire tone remote by a spectra tac comparator with a satellite receiver in our building's basement (hole in coverage). Subscribers are using MTS2000 portables. I recently acquired a 350w VHF Quantro and a few model 3 XTS5000 portables and want to upgrade our system to P25 mixed mode (to allow MTS2000 coverage to continue). I am thinking I'd use an Astro tac voter and an Astro receiver programmed for mixed mode. Will that configuration pass voted analog audio and P25? I feel like a Astro DIU is probably in order here but I'm sure I'm about to find out. Has anyone successfully set up a mixed mode voting system? Eventually, all subscribers will be P25 but for now, there will be MTS2ks that will need to access the system. All info is appreciated.

[alex]

If this is all within a single building:

Replace the SpectraTac with an Astro Tac Comparator

Replace the receiver to be an AstroTac Receiver with either a v.24 daughter card or a astro modem. If you can do astro modems I would strongly suggest it because it reduces the complexity of what is required.

Make sure you have two clean pairs that run from your receiver in the basement to the comparator (astro modem only, I'll assume you go this direction unless otherwise noted).

You will need to put a DIU on the Astro Tac Comparator in order to key the system (as it will be keyed not by tone but Astro Signaling (which is what the DIU's job is outside of demodulating the digital audio). The DIU will communicate over V.24 to the Comparator so one card in your AstroTac comparator will be a serial while the other one will have two astro modems.

Put an astro modem in your Quantro.

Connect everything up and do some programming and you will have a voted astro system.

(note, above is over simplified but is a basic shopping list).

Ninja Edit - The Spectratac will work for years to come, keep some spare cards and a power supply handy for emergencies.....

Alex

[cjrd1993]

I'll never ditch my trusty MTR and Spectra Tac. Maybe display them in a museum? I love our system as it has that old "sheriff repeater system" creaky sound. But time goes on and we are tired of the old MTS portables. I kinda figured the DIU was going to be needed. Sure would've been nice if mother M made a P25 MTR. Gotta figure out how to miracle this 300lb flame thrower to the roof of our building (60 steps up from elevator limit). Once there, it will crumble with the building.
So, all you said makes sense. I'm just confused on how analog audio is brought up from basement receiver. I get that the modem will bring up P25, but is there a 2 pair wireline coming up for the analog audio or is it sent up via modem and the DIU converts? Forgive if it seems like a dumb question, kinda new to P25. We never considered switching but the market is starting to flood with surplus and the bottom fell out on pricing.

[alex]

Good question w/two answers:

If the transport is Astro Modem: The Modem sound will stop and you will get analog voice. Once the voice is gone the modems sync back up. So the modem stops for analog voice. I've been told (though I didn't really vet it myself but it's likely in one of the many astro manuals) that there is a pulse or underlying subaudiable tone that says I'm done sending voice and start up the data stream again. I'll have to listen to one of ours at some point and see.

If the transport is V.24 Serial it is sent in parallel with voice on another circuit.

Alex

[cjrd1993]

Very helpful. Thank you for all the info. It helps me put together a shopping list. Happy holidays!