TDMA Heard on my BCD396xt

[kc5voa]

Listening to Texas TWARN system on my 396xt. Hearing TGID 4025 (U of Texas Police). Just discovered in Radio Reference that their mode is TDMA. Is this happening to anyone else? I'm assuming that they switched back to standard P25. Now I'm creating a TDMA bank and putting in ID's to see if I can pick up more. Neat.

 

[KevinC]

Listening to Texas TWARN system on my 396xt. Hearing TGID 4025 (U of Texas Police). Just discovered in Radio Reference that their mode is TDMA. Is this happening to anyone else? I'm assuming that they switched back to standard P25. Now I'm creating a TDMA bank and putting in ID's to see if I can pick up more. Neat.

I would venture to guess that TG is actually DDM and not TDMA only and a FDMA radio affiliated to it.

 

[Outerdog]

What you're hearing is a talkgroup reverting to Phase 1 operation for whatever reason. Usually because a subscriber not capable of Phase 2 TDMA operation has affiliated to the talkgroup.

 

[kc5voa]

Thanks for the info. I agree about the switching back to phase 1. I wonder if there are more in the TWARN system that switched back.

 

[KevinC]

Thanks for the info. I agree about the switching back to phase 1. I wonder if there are more in the TWARN system that switched back.

Yes, definitely.

 

[MTS2000des]

They aren't "switching back" as in a system level change. It is how DDM (dual dynamic mode) works. If a legacy susbscriber affiliates with a DDM talk group, it is downgraded to FDMA so long as 1)-that subscriber remains affiliated 2)-an inactivity timer (default is usually 12 hours). If the subscriber de-affiliates, powers down, etc than the talkgroup operates in TDMA mode.
75 percent of the talkgroups on my Astro 25 system are DDM, and I regularly monitor the system for affiliations of legacy radios on talk groups that should primarily be running in TDMA mode, and mostly notice that it's one single radio from a nearby agency parked on a talk group thus downgrading that talk group for the duration.

 

[GTR8000]

...mostly notice that it's one single radio from a nearby agency parked on a talk group thus downgrading that talk group for the duration.

Ridiculous. How long has the talkgroup been provisioned? Surely that one agency can pony up for an APX by this point, instead of wasting a full channel for one lousy radio. That crap would never fly in some locations around here. Decisions were made to strap all talkgroups TDMA and buy a capable radio if you want to operate on the system, rather than wasting money on DDM + having some cheap agencies using 20 year old XTS/XTL radios because there's no incentive to upgrade.

 

[a417]

someone pulled a radio out of the depot, or are running a spare car with a really old radio in it.

 

[MTS2000des]

Ridiculous. How long has the talkgroup been provisioned? Surely that one agency can pony up for an APX by this point, instead of wasting a full channel for one lousy radio. That crap would never fly in some locations around here. Decisions were made to strap all talkgroups TDMA and buy a capable radio if you want to operate on the system, rather than wasting money on DDM + having some cheap agencies using 20 year old XTS/XTL radios because there's no incentive to upgrade.

We don't have money pits around here. We have four cities PDs sharing a single talk group because they don't want to pony up what it COSTS us to give them separate dispatch consoles with dedicated dispatchers. Many of them have XTS radios and are piecemeal replacing them with APX, Kenwood VP6000s, and Harris XL's as budgets allow.

Many hospitals still have XTL5000 control stations purchased on 2004 UASI funding in their facilities. We have strapped TDMA talkgroups where we can but our countywide mutual aid stuff must be DDM. The "big city" down the street from us has a 28 channel 2019.2 with DSR, and a few hundred more active talk groups on their core than mine, and guess, what- lots of legacy radios in use. SuperBowl 2018 we programmed over 500 of them for cache use and issued them out for that event.

It must be nice to have unlimited budgets.