TDOT - Region 3 Dispatch, TGID 47152

[linuxskynyrd]

A question about TDOT - Region 3 Dispatch, TGID 47152

Please forgive me for asking what some will undoubtedly think is a stupid question and I will in advance admit that i'm a novice, (aka idiot), but can anyone explain why on a given day, this talk group has seemingly constant communications and the next day, virtually nothing at all? I can see the trucks working incidents online via the TDOT cameras so I know they're hard at it, just nothing on the scanner, (nothing today but they may be back tomorrow!).

I've reprogrammed my scanner until it's smokin' only to come to the conclusion that it's not my scanner or the freeks, (I live in mid TN and use the Smyrna TN frequencies as none of the others i've tried have been successful). Yesterday, 5/1/25, ProScan logged approx. 300 hits from this talk group, (loud and clear) but today, only 2.

I have the BCD996P2.

Also, I don't have this issue with any of the other agencies that I regularly listen to.

Thanks,

linuxskynyrd

 

[ToTheBitCave]

Definitely not a stupid question; it just shows you’re observant/clever. Which site are you listening to? If there are no radios affiliated with that talk group on the particular site you’re listening to on TACN, that site will not transmit traffic with that talk group (to save RF resources). I am not a radio admin, but I’m sure there’s a setting to toggle where certain talkgroups WILL transmit across the entire system regardless of TG affiliations on a site (to broadcast to all SUs across the entire system for the announcement). I thought TG 1 was for this purpose (not sure)?

There were times where I noticed Knoxville talkgroups popping up on the site I listen to (which is over four hours away). I imagine there was a radio affiliating with that talkgroup on whatever site I was near (maybe someone on vacation or someone accidentally on the wrong TG and their radio had it programmed for whatever reason). I think there is also a setting to prevent radios from affiliating with talkgroups outside of a certain area or certain sites, but again I am guessing.

Also, a question for anyone who knows, are “simulcast” sites designed to transmit all TG activity to all sites regardless of affiliations?

 

[linuxskynyrd]

Hello and thank you for your reply.

I'm not sure if I understand your question but I was listening to "TN - Department of Transportation HELP" trucks and dispatch.

The TGID's in the particular group i have programmed are:

DOT HELP R3 - 47152
DOT HTAC1 R3 - 47156
DOT HTAC2 R3 - 47161
DOT HTAC3 R3 - 47163

The frequencies i have programmed in for this group are:

(as listed on Tennessee Advanced Communications Network (TACN) Site: Smyrna)

Smyrna
853.4000
851.0625
851.4000
851.6750
852.0375
852.5750
852.9500
853.6750
853.9875

I was listening to the "Green TDOT Highway HELP Trucks". You can also hear them on Broadcastify via the link below:

Region 3 Dispatch - Nashville/TN - Department of Transportation HELP Group Calls Live

47152 Group Calls Live

www.broadcastify.com

One thing to note is the last hit i received was at 4:07 am on 5/2/25, (this morning). 4:07 am is also the time stamp for the last hit on the Broadcastify site.

Is anyone else able to receive them consistantly because I cannot consistantly receive the TDOT transmissions. I'm certain it's not a distance issue as I am in their region. As stated earlier, one day, I get hundreds of hits and the next day, zero. I simply don't understand why that is and "do I have to get used to it because that's just the way it is".

If it were OTA TV signals, it would make more sense to me.

I'm sure i've made myself clear as mud.

linuxskynyrd

 

[linuxskynyrd]

In my exhausting quest to understand, the answer to the earlier question would be Site 064. I have to thank richard4537212 and the title to his post:
"TACN Site 049 Cleveland" for the clue to which "Site" I am trying to listen to. It is the same site that I receive La Vergne and Smyrna, TN public safety traffic.

 

[linuxskynyrd]

I would also like to thank the "moderators" for their patience with newb's like me and the fact that they placed my OP in the correct forum.

 

[KevinC]

I would also like to thank the "moderators" for their patience with newb's like me and the fact that they placed my OP in the correct forum.

You're very welcome!

 

[jblackst]

In my exhausting quest to understand, the answer to the earlier question would be Site 064. I have to thank richard4537212 and the title to his post:
"TACN Site 049 Cleveland" for the clue to which "Site" I am trying to listen to. It is the same site that I receive La Vergne and Smyrna, TN public safety traffic

Something to be aware of, on a system like TACN, traffic on a particular talk group is only transmitted on a particular tower site when a subscriber radio is connected (affiliated) to that same site. That explains why you only hear Knoxville traffic occasionally; there's likely only a subscriber affiliated to that talk group on your tower site when someone (maybe a supervisor) from Knoxville drives to Nashville.

That's one of the ways that a trying radio system can be setup to save bandwidth (and from having to have dozens of frequencies available on every tower site).

If you're monitoring a Simulcast node on the system (like Knoxville or Chattanooga) the rules are slightly different. All traffic from a talk group on the simulcast node to transmitted from every site of the simulcast node at the same time, irregardless of whether or not anyone is actually affiliated to a particular tower on the simulcast node. Practical in smaller areas, but completely impractical across mega sized systems.

 

[surfacemount]

Can you hear it on broadcastify when you can't on yours?

That might help resolve it.

 

[buddrousa]

Post #7 is the best answer if not TDOT unit is currently connected to the site you are monitoring then not TDOT traffic will be transmitted on that site.

 

[linuxskynyrd]

Can you hear it on broadcastify when you can't on yours?

That might help resolve it.

Hi and yes, sometimes. But I noticed that sometimes, i can hear TDOT on my rig and it's not on broadcastify.

I've come to accept that "that's just the way it is" because of "jblackst" and "budrousa's" comments. As i've paid more attention to the communications, it seems when a TDOT unit is closer to my location, this is when it starts booming, something that I didn't realize before. It is, however, disappointing because the TDOT calls are very interesting. Because of listening to them while watching online, I've gained new respect for them, given the dangers they are exposed to and what they are able to to with those trucks!

I thank you all for the education!

linuxskynyrd

 

[linuxskynyrd]

I should also thank "ToTheBitCave" as he explained the issue almost immediately. Unfortunately, i didn't understand what he was saying, (i'm learning the language). Again, thanks to all.

linuxskynyrd

 

[jblackst]

Think of it like this: at home if there's nobody using a particular room in the house, the lights turn off to save electricity. Then the instant someone enters the room the lights turn back on.

Now upscale that to TACN. Your house is TACN and each room is a tower site. You are a user on talk group 123. Your spouse is the dispatcher on the same talk group and is positioned in the office. The lights stay on in the office, since your dispatcher will be there the whole shift. However, as you walk thru the house, lights (sites) turn on and off as needed to illuminate your path. Your friend is in your garage, 'scanning talk group 123', so the lights there are off. Your friend won't see any light (or hear any conversation) until you come into the garage and the light (tower) turns on for your presence.

The radio system is doing the same for users. If there aren't and users in your garage (adjacent tower site), you won't hear any of their traffic. Other sites that they occupy will pass traffic normally.

As a scanner user, you can sometimes improve your scanning experience by scanning a different tower that has a higher likelihood of having the traffic (and users) you want to listen to. YMMV 😉

 

[jblackst]

Definitely not a stupid question; it just shows you’re observant/clever. Which site are you listening to? If there are no radios affiliated with that talk group on the particular site you’re listening to on TACN, that site will not transmit traffic with that talk group (to save RF resources). I am not a radio admin, but I’m sure there’s a setting to toggle where certain talkgroups WILL transmit across the entire system regardless of TG affiliations on a site (to broadcast to all SUs across the entire system for the announcement). I thought TG 1 was for this purpose (not sure)?

There were times where I noticed Knoxville talkgroups popping up on the site I listen to (which is over four hours away). I imagine there was a radio affiliating with that talkgroup on whatever site I was near (maybe someone on vacation or someone accidentally on the wrong TG and their radio had it programmed for whatever reason). I think there is also a setting to prevent radios from affiliating with talkgroups outside of a certain area or certain sites, but again I am guessing.

Also, a question for anyone who knows, are “simulcast” sites designed to transmit all TG activity to all sites regardless of affiliations?

To my knowledge, simulcast sites (which are collections of different tower sites with the same site ID) transmit all traffic across all of the simulcasted towers in that particular site, regardless of whether or not and field units are actually connected to a particular tower site on the simulcast system. Like smaller systems inside the higher TACN system. In the Knoxville Simulcast there are 5 independent tower sites around the county. All 5 carry all the same traffic all of the time. It's like a fire hose.

Chattanooga, Knoxville, Johnson City, Washington Co, NW GA all have simulcast sites within TACN. There may be more.

It gets a little more complicated, as local agencies generally only connect within a certain distance of their home area. State agencies however can generally connect to any tier across the state.

For example: a city fire chief from Knoxville drives to Nashville while his radio is on. It will generally stay connected from Knoxville to roughly Rockwood, then the system will deny him since the talk group he's using doesn't have permission that far away. It saves resources on the radio system.

A TDOT supervisor from Knoxville driving to Nashville, however, would have a different experience as their radio would stay connected with Knoxville all across the state, since their agency jurisdiction is statewide.

These systems are much more complex than we give them credit for. At some levels it's hilarious to think of all the infrastructure in place just to let two "dog catchers" talk to each other, while being robust enough to facilitate statewide communications for TEMA, THP, and dozens of air ambulances.

 

[surfacemount]

To my knowledge, simulcast sites (which are collections of different tower sites with the same site ID) transmit all traffic across all of the simulcasted towers in that particular site, regardless of whether or not and field units are actually connected to a particular tower site on the simulcast system. Like smaller systems inside the higher TACN system. In the Knoxville Simulcast there are 5 independent tower sites around the county. All 5 carry all the same traffic all of the time. It's like a fire hose.

Chattanooga, Knoxville, Johnson City, Washington Co, NW GA all have simulcast sites within TACN. There may be more.

It gets a little more complicated, as local agencies generally only connect within a certain distance of their home area. State agencies however can generally connect to any tier across the state.

For example: a city fire chief from Knoxville drives to Nashville while his radio is on. It will generally stay connected from Knoxville to roughly Rockwood, then the system will deny him since the talk group he's using doesn't have permission that far away. It saves resources on the radio system.

A TDOT supervisor from Knoxville driving to Nashville, however, would have a different experience as their radio would stay connected with Knoxville all across the state, since their agency jurisdiction is statewide.

These systems are much more complex than we give them credit for. At some levels it's hilarious to think of all the infrastructure in place just to let two "dog catchers" talk to each other, while being robust enough to facilitate statewide communications for TEMA, THP, and dozens of air ambulances.

This is the correct answer, and it's why I generally don't say the subscriber has to be on that specific tower without some additional information.

TACN is a monster. And, it works

 

[INDY72]

If you happen to travel to AR, MS, LA, NC, SC etc... This also applies to the statewide Trunked Radio Systems in use there. Happy monitoring! As for the controlling of specific TG, in certain areas, this is called "geofencing", and is used also to allow a radio to only affiliate with sites in its "fence" walls. Try to affiliate without forced affiliation and you get bonked.

 

[ka4bni]

To add to the previous postings, if you live in a location where you can receive either the TN Towers or West Nashville (Sullivan's Ridge) sites, those will be the sites that "should" have a Help truck affiliated to them most of the time. The other sites are usually hit and miss on Help Truck affiliations.