Finding system details

[N0BDW]

Howdy,

If I have a radio that is on a system but otherwise know essentially no information about the system, how can I get enough information to program the system into my BCD536HP? Is that even possible?

Here is what I know:
It is a VHF P25 Phase 2 TDMA system
Where each tower site is physically located

I do not know what frequencies are involved or which are control channels or what the talkgroup IDs are.

This is a brand new system that is just being built; there are only a handful of radios that have been issued, so I can transmit on any of the talk groups that I have access to in order to determine TGIDs.

Thanks!

P.S. Yes, I could just ask for this information, but we were supposed to be up and running on this system by August. I just got the first 2 portables this evening. We probably won't actually be up and running with it until after the new year. It is a slow process and I really don't want to bug the one guy with technical knowledge working on the project for this. He has a lot on his plate.

 

[N0BDW]

Actually I might have the talkgroup IDs... is it possible the TGIDs are just 2-3 digits each, i.e. "95" and "105"? I do have a list of the talkgroups and they are IDed in that manner.

 

[Thunderknight]

Actually I might have the talkgroup IDs... is it possible the TGIDs are just 2-3 digits each, i.e. "95" and "105"? I do have a list of the talkgroups and they are IDed in that manner.

Yes.

 

[Ubbe]

Use the Close Call function to get one frequency while you transmit with one portable. Transmit with one portable and at the same time transmit with the other on a different talk group to get a second frequency. Repeat to possible get more frequencies as the voice channels goes thru its cycle, or wait until someone else use the system and repeat the procedure.

Use "rev" (func+8) to get the repeater frequencies.

You probably need to travel to other sites to get more frequencies unless it is a simulcast system.

Make a system and program the repeater frequencies you found and use the "Trunking Discovery" function to get the talk group id's.

/Ubbe

 

[troymail]

Looking at the licenses, it appears that KEA535 was changed/authorized to be a trunked system (February?).

ULS License - Public Safety Pool, Trunked License - KEA535 - LIVINGSTON, COUNTY OF - Frequencies Summary

There is also another license (WQXA974) that seems to have many of the same frequencies assigned to it.

ULS License - Public Safety Pool, Trunked License - WQXA974 - LIVINGSTON, COUNTY OF

If it were me, I'd manually create a new P25 trunked system, create a site for each of the sites listed on these licenses (or at least the ones closest to your location), program in the site (repeater/FB) frequencies into each of the sites you created with what is listed on the licenses, probably create a couple of talkgroups such as what you've listed above (95, 105, etc.), and put the newly programmed system into "ID Search" mode.

You may not hear much if the system isn't live yet and/or isn't busy but you should at least see the "DAT" symbol on the screen for one or more sites which would indicate that the radio is detecting/processing a control channel for one of the sites.

 

[bearcat]

Use the Close Call function to get one frequency while you transmit with one portable. Transmit with one portable and at the same time transmit with the other on a different talk group to get a second frequency. Repeat to possible get more frequencies as the voice channels goes thru its cycle, or wait until someone else use the system and repeat the procedure.

Use "rev" (func+8) to get the repeater frequencies.

You probably need to travel to other sites to get more frequencies unless it is a simulcast system.

Make a system and program the repeater frequencies you found and use the "Trunking Discovery" function to get the talk group id's.

/Ubbe

I do not believe that the "REV" function will provide proper freqs. VHF systems do not use a standard offset like UHF system do. Close Call would give you the repeater input freqs only.

 

[N0BDW]

Looking at the licenses, it appears that KEA535 was changed/authorized to be a trunked system (February?).

ULS License - Public Safety Pool, Trunked License - KEA535 - LIVINGSTON, COUNTY OF - Frequencies Summary

There is also another license (WQXA974) that seems to have many of the same frequencies assigned to it.

ULS License - Public Safety Pool, Trunked License - WQXA974 - LIVINGSTON, COUNTY OF

If it were me, I'd manually create a new P25 trunked system, create a site for each of the sites listed on these licenses (or at least the ones closest to your location), program in the site (repeater/FB) frequencies into each of the sites you created with what is listed on the licenses, probably create a couple of talkgroups such as what you've listed above (95, 105, etc.), and put the newly programmed system into "ID Search" mode.

You may not hear much if the system isn't live yet and/or isn't busy but you should at least see the "DAT" symbol on the screen for one or more sites which would indicate that the radio is detecting/processing a control channel for one of the sites.

Thanks, I did try something like that. I created a new system, created a new site, and put in each of the frequencies that I thought might be associated with the system (looking at the licenses). I then ran an ID search on it and had no hits (even while transmitting).

Use the Close Call function to get one frequency while you transmit with one portable. Transmit with one portable and at the same time transmit with the other on a different talk group to get a second frequency. Repeat to possible get more frequencies as the voice channels goes thru its cycle, or wait until someone else use the system and repeat the procedure.

Use "rev" (func+8) to get the repeater frequencies.

You probably need to travel to other sites to get more frequencies unless it is a simulcast system.

Make a system and program the repeater frequencies you found and use the "Trunking Discovery" function to get the talk group id's.

/Ubbe

Close call doesn't pick up anything when I transmit on the system. It does pick up the conventional analog channels that are programmed.

It is a simulcast system.

Yes.

Thanks.

 

[UPMan]

For VHF, you should really just bother the system tech for the frequencies. There is no way to easily infer the frequencies in use for voice calls. And, since there is a continuous transmission from each tower on the control channel frequency, it is very unlikely you'd ever get a Close Call hit on the voice channels. You might be able to determine the voice channels using something like a HackRF (where you cans see the spectrum +/- 10 MHz from the center frequency), visually watching the spectrum around the control channel frequency to find frequencies that go active concurrent with a voice channel grant, but that would be both time consuming and unreliable.

 

[N0BDW]

For VHF, you should really just bother the system tech for the frequencies. There is no way to easily infer the frequencies in use for voice calls. And, since there is a continuous transmission from each tower on the control channel frequency, it is very unlikely you'd ever get a Close Call hit on the voice channels. You might be able to determine the voice channels using something like a HackRF (where you cans see the spectrum +/- 10 MHz from the center frequency), visually watching the spectrum around the control channel frequency to find frequencies that go active concurrent with a voice channel grant, but that would be both time consuming and unreliable.

Okay, thanks. I'll bother him.

 

[k3fs]

The advanced analysis features that were announced and yet to be delivered, would supply this information. As it is the 436 and 536 lack control channel output or IF output. So you cannot even use a trunker program to get info. You would need another radio for this use.

 

[N0BDW]

Okay, so I got the frequencies and have tried setting up the system in Sentinel. I've attached screenshots of what I think are the relevant bits.

When I fire up the scanner and hold on the LIVINGSTON P25 X2-TDMA system it shows:
Full signal bars
LIVINGSTON P25 X2-TDMA (HOLD)
LIVONIA
ID Searching...


If I hit the channel button it shows:
Full signal bars
LIVINGSTON P25 X2-TDMA (HOLD)
ZONE A
FIRE DISPATCH (HOLD)

But keying up on that talkgroup doesn't do anything... either in ID search or held on the talkgroup. What am I missing?

Interestingly enough when I key up the signal bars drop off entirely or flash on and off, but there is no other indication on the scanner that anyone is transmitting.

 

[troymail]

Okay, so I got the frequencies and have tried setting up the system in Sentinel. I've attached screenshots of what I think are the relevant bits.

When I fire up the scanner and hold on the LIVINGSTON P25 X2-TDMA system it shows:
Full signal bars
LIVINGSTON P25 X2-TDMA (HOLD)
LIVONIA
ID Searching...


If I hit the channel button it shows:
Full signal bars
LIVINGSTON P25 X2-TDMA (HOLD)
ZONE A
FIRE DISPATCH (HOLD)

But keying up on that talkgroup doesn't do anything... either in ID search or held on the talkgroup. What am I missing?

Interestingly enough when I key up the signal bars drop off entirely or flash on and off, but there is no other indication on the scanner that anyone is transmitting.

Unless someone told you for sure that it is an X2 system, the problemishes is likely you've programmed it incorrectly.

Just program it as a P25 trunk system, not X2.

 

[UPMan]

Also, do not key up within a few feet of the scanner. At best, the strong signal will dramatically desense the receiver (RF AGC will cut in). At worst, it can damage the scanner.

Next, I'd use ID Search mode for initial testing, so that the scanner will stop on any transmission on the system.

 

[N0BDW]

Also, do not key up within a few feet of the scanner. At best, the strong signal will dramatically desense the receiver (RF AGC will cut in). At worst, it can damage the scanner.

Next, I'd use ID Search mode for initial testing, so that the scanner will stop on any transmission on the system.

Tried moving to the next room over with no difference made.

By ID search mode you mean this?

Full signal bars
LIVINGSTON P25 X2-TDMA (HOLD)
LIVONIA
ID Searching...

Unless someone told you for sure that it is an X2 system, the problemishes is likely you've programmed it incorrectly.

Just program it as a P25 trunk system, not X2.

It is a TDMA system. I don't know what "X2" is but if it is "phase 2" then yes-- it is phase 2.

I tried programming it as just a regular P25 Trunk system and had the same results. No audio, doesn't stop on any talkgroups, ID search shows nothing.

 

[N0BDW]

Pardon my ignorance. This is my first experience working with either P25 or trunking.

Does the order the frequencies are programmed in matter?
i.e. does the control channel have to be listed first?
I don't know what the control channel is. I just have a list of "Trunking Base RX" and "Trunking Base TX" frequencies.

Also I know for sure some of the frequencies I was given will eventually be rolled into the system but are currently in use as analog conventional channels. I've tried it both with them in the list and without them, with no improvement.

 

[troymail]

Pardon my ignorance. This is my first experience working with either P25 or trunking.

Does the order the frequencies are programmed in matter?

i.e. does the control channel have to be listed first?

No

In fact, typically for P25, you should really only need the active control channel frequency programmed for each site (but you probably want others like alternate control channel frequencies programmed as well).

 

[N0BDW]

No

In fact, typically for P25, you should really only need the active control channel frequency programmed for each site (but you probably want others like alternate control channel frequencies programmed as well).

Okay. I've got the control channel (only) programmed into the site. I've tried this on both the P25 TRUNK and P25 X2-TDMA systems I've set up. When I go into discovery I get full signal bars, but they blink, and LNK occasionally blinks. I never see DAT, and I never get any hits.

 

[troymail]

Okay. I've got the control channel (only) programmed into the site. I've tried this on both the P25 TRUNK and P25 X2-TDMA systems I've set up. When I go into discovery I get full signal bars, but they blink, and LNK occasionally blinks. I never see DAT, and I never get any hits.

The simulcast systems are a pain.... particularly if you are between towers on a given site. I can put my radios in one spot in the house and see / hear nothing and then move it somewhere else (as few as a matter of inches) and I get a good signal.

Although not perfect and/or optimal, another thing you can try - beyond just moving the radio around to various locations - is to get close to a tower/transmitter (closer to one than another) and see if you can receive anything.

Again, if the system isn't active, you may not hear anything but you should ad least see the DAT symbol on the display indicating the radio is trying to process the control channel.

 

[MFCJR]

I'm sure you checked but make sure Fire Dispatch is turned on in Service Types and Monitor is on. Sometimes it's just the little things that are overlooked.

 

[N0BDW]

The simulcast systems are a pain.... particularly if you are between towers on a given site. I can put my radios in one spot in the house and see / hear nothing and then move it somewhere else (as few as a matter of inches) and I get a good signal.

Although not perfect and/or optimal, another thing you can try - beyond just moving the radio around to various locations - is to get close to a tower/transmitter (closer to one than another) and see if you can receive anything.

Again, if the system isn't active, you may not hear anything but you should ad least see the DAT symbol on the display indicating the radio is trying to process the control channel.

Current situation is that I only have the control channel programmed, no talk groups programmed (so it is in ID Search mode), and if I enter Discovery mode the DAT indicator only blinks on briefly occasionally. It never gets sold. Does that sound like a simulcast issue?

If so, and considering I'm fairly limited on where the scanner/antenna can be located... what options do I have?

How come the radio can handle the simulcast from the same spot, but the scanner cannot?

Your avatar is spot on for my current feelings, ha.

I'm sure you checked but make sure Fire Dispatch is turned on in Service Types and Monitor is on. Sometimes it's just the little things that are overlooked.

It was. I've deleted the talk group entirely now, though.