Complicated question about scanning between phase 1 and phase 2 systems

[tgalveston]

I work for an agency that operates on a county simulcast system that is part of a statewide P25 trunked system. This particular county was the most recent to join the stateside system (within the past 2 years) and is the first to be PHASE 2 with the rest of the state currently PHASE 1 and planned to be PHASE 2 within the next several years.

Neighboring agencies (neighboring county) that operate PHASE 1 are programmed into our radios and we can communicate with them without issue. In doing so, the radio switches to that county’s simulcast cell when the radio is turned to that talkgroup. In my research, I have found that PHASE 2 interoperates with PHASE 1 by downgrading to PHASE 1. Please correct me if I’m wrong.

The issue arises here: We are unable to scan PHASE 1 talkgroups in our scan list. We can add them but they do not scan. The radios are programmed in a way where even if a PHASE 1 talkgroup is programmed in a zone full of PHASE 2 talkgroups, the radio switches to that TG’s home simulcast cell when you switch to that talkgroup.

We were told by some very uneducated people during initial training that if we were given the ability to scan that other counties TG’s that we would degrade the capacity of that system. On a side note, these are the same people who allowed the entire fleet of mobile radios in the largest cell of this decades old statewide system to go online with a programing error that kept every single mobile radio from having the ability to scan all together unless the microphone holder was grounded. Yes, they failed to allow for off hook scanning in CPS and now we await a promised WiFi OTA reprograming which I’m told is causing it’s own set of issues.

But I digress. I’m not an expert but this reasoning confuses me. The end used would only take up a slot on the phase 1 system if they keyed the radio, right? I referred to these individuals as uneducated, but they might very well be correct. And that’s my question. On a Motorola based P25 trunking system, can a Phase 2 radio scan Phase 1 TG’s without degrading that Phase 1 system? Thank you for your answers.

 

[MTS2000des]

Without knowing particulars of your system, in Motorola networks, DDM (dual dynamic mode) is configurable by system managers to allow legacy radios (FDMA) to downgrade a talk group by affiliating on that talkgroup forcing all radios on that TG to operate in FDMA vs TDMA. With that being said, you may not be able to scan FDMA talkgroups if there aren't any FDMA subscriber affiliated on said groups. Again, depends on how the system is setup but DDM is a common option to allow older radios to access a network. This sounds like what you are experiencing.

The system I manage has most dispatch talkgroups set for DDM to allow mutual aid and the "stragglers" of legacy equipment to operate. Once they de-register, those talk groups revert to TDMA. We have set a date of 1/1/2026 for all legacy radios to be off the system at which time, we will change the TG type to TDMA only.

 

[jeepsandradios]

As said above without specifics on your system alot of what we can do is guess. In trunking some folks use site preference on talkgroups in radios, as well as in the system. A talkgroup can be "roamable" to use any cell in the system, but the codeplug could have a preference to alwasy use abc site and not roam to def site. This is all decided by the powers to be in a fleetmapping session. Depending on resources on your simulcast cell hey may not want FDMA talkgroups on it. If you have a 4-5 channel system that could tie up multiple voice paths and limit your resources. Scan jsut adds another level of confusion and programming. I have worked on systems similar to what you describe and when you are affiliated to your site unless a FDMA talkgroup is affiliated approved and on the air your radio wont hear it.

 

[Motoballa]

Based on the users prior posts it appears they may be referring to Oakland County on MPSCS and while I know little about the system, just by scrolling through it looks like Oakland County is TDMA while most of the other system talkgroups if not all are still FDMA. MTS is correct when is comes to DDM but the OP mentioned it the other way around which doesn't entirely make sense unless we use jeeps response about the resources and site list assignment.

 

[MississippiPI]

You would think the radio shop would know.


Be safe