# TIII systems: voice frequencies from channel numbers?

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#### W4KRR

##### Member
Using DSD+, I found a system that displays, at the bottom of the Event Log:
TIII Site:L13-1.1 DCC 1

In the Channel activity window, it displays channel numbers as follows:
1845
1846
2365
2366
2381
2382

I have identified two frequencies: 464.8625, and 464.7625.

Can the voice frequencies be determined by these channel numbers? Systems that identify as CON+ or CAP+ show the channel numbers as 1, 2, 3, 4, etc.

#### KevinC

##### Other
Super Moderator
Wild guess, but I'd try 461.5125...assuming my math is correct.

#### EricCottrell

##### Member
Hello,

Tier 3 can follow a classic Freq = (LCN - 1) * Step + Base formula. DSD+ considers each slot to be a channel, so 1845 and 1846 are the same frequency, for example. You need to divide the higher number by two to get the actual LCN. So the LCNs are:
923
1183
1191

You really need to tie at least one of the two frequencies you identified to the channel number.

It appears the 2365/2366 is 464.7625 and 2381/2383 is 464.8625, but the base frequency (LCN 1 = 449.9875) does not seem to be quite correct. I would try 461.5125 as suggested. That is possibly 1845/1846.

73 Eric

#### KevinC

##### Other
Super Moderator
Hello,

Tier 3 can follow a classic Freq = (LCN - 1) * Step + Base formula. DSD+ considers each slot to be a channel, so 1845 and 1846 are the same frequency, for example. You need to divide the higher number by two to get the actual LCN. So the LCNs are:
923
1183
1191

You really need to tie at least one of the two frequencies you identified to the channel number.

It appears the 2365/2366 is 464.7625 and 2381/2383 is 464.8625, but the base frequency (LCN 1 = 449.9875) does not seem to be quite correct. I would try 461.5125 as suggested. That is possibly 1845/1846.

73 Eric

I used a base of 449.98125.

ETA...

With a channel spacing of 6.25 kHz.

Last edited:

#### W4KRR

##### Member
I think #2382 is 464.8625, and #2365 is 464.7625. I am monitoring 461.5125, but nothing so far. However it is nighttime and it may not be a busy enough system. I am also trying other frequencies while looking for the "Site L13-1.1" indication.

#### jonwienke

If we're talking Tier III DMR/MotoTRBO, wouldn't the channel spacing be 12.5KHz? TDMA instead of FDMA and all that...

#### EricCottrell

##### Member
Hello,

I noticed Tier 3 voice channels on the Hytera systems around here look like DMR conventional. They do not carry site information, unlike Motorola. You need to monitor the control channel, wait for 1845/1846 to become active and then search while it is active.

73 Eric

#### KevinC

##### Other
Super Moderator
If we're talking Tier III DMR/MotoTRBO, wouldn't the channel spacing be 12.5KHz? TDMA instead of FDMA and all that...

In the context of how the radio actually works probably yes, but in the context of how DSD+ interprets the channel numbers this formula appears to work.

#### KevinC

##### Other
Super Moderator
I think #2382 is 464.8625, and #2365 is 464.7625. I am monitoring 461.5125, but nothing so far. However it is nighttime and it may not be a busy enough system. I am also trying other frequencies while looking for the "Site L13-1.1" indication.

Based on your location, the 2 known frequencies and 1 suspect frequency, the below license is a likely candidate...

WPVZ205 (MIDWAY TOWER MANAGEMENT INC) FCC Callsign Details

#### pctek961

##### Member
Citation Communications TIII

Some channels that I discovered, system not very busy, mostly taxi or shuttle service.

Citation Communications Lantana
461.5125 Ch 1845/1846
464.7625 Ch 2365/2366

Citation Communications Singer Island
451.9625 Ch 317/318
452.2125 Ch 357/358
464.8125 Ch 2373/2374

#### W4KRR

##### Member
Based on your location, the 2 known frequencies and 1 suspect frequency, the below license is a likely candidate...

WPVZ205 (MIDWAY TOWER MANAGEMENT INC) FCC Callsign Details

Apparently this is the system. I have now confirmed:
1845/1846 = 461.5125
2365/2366 = 464.7625
2381/2382 = 464.8625

The system is right on the edge of me being able to receive it too clearly, but at least I have identified it. Thanks for the help.

#### KevinC

##### Other
Super Moderator
Apparently this is the system. I have now confirmed:
1845/1846 = 461.5125
2365/2366 = 464.7625
2381/2382 = 464.8625

The system is right on the edge of me being able to receive it too clearly, but at least I have identified it. Thanks for the help.

Cool!

For any additional channel numbers use this formula...

Multiply the odd channel number by .00625 then add 449.98125 to the product for the frequency.

#### nd5y

##### Member
Can a DMR Tier 3 system have more than one base/offset or a different base/offset for different sites?
There is one near here that appears to have more than one band plan.

DSD+ 1.01 shows the following

Site 1-1.1
451.45 ch 3 and 4 (LCN 2)
452.025 ch 95 and 96 (LCN 48)

Site 1-1.2
The transmit frequency appears to be off. It's either 464.44375 or 464.45 and too low. There is no FCC license so I don't know what it's supposed to be.
DSD+ shows ch 323 and 324 (LCN 162). Either way it appears to be different than the other site.

If I use the formula posted earlier and change the base freq to match the first site then ch 323 should be 453.45.

#### Raccon

##### Member
Can a DMR Tier 3 system have more than one base/offset or a different base/offset for different sites?
The base can be different for different sites.

#### TampaTyron

##### Beep Boop, Beep Boop
Motorola's Tier 3 can have 4 different bases. I was told that this allows them to cover weird European freq plans AND allows multiple bands in one system (vhf, uhf, 800, 900, etc). TT

#### mrscanner2008

##### Member
Using DSD+, I found a system that displays, at the bottom of the Event Log:
TIII (MOT)Site:S2-1.2
TIII (MOT)Site:S2-1.3
TIII (MOT)Site:S2-1.4
TIII (MOT)Site:S2-2.1
TIII (MOT)Site:S2-2.2

In the Channel activity window, it displays channel numbers as follows:
CH 17-18 for site 1.4
CH 7-8 for site 1.2
CH 27-28 for site 2.1

I have identified two frequencies:
410.6625 for site 1.3
412.9375 for site 1.3
412.8125 for site 1.2
412.4375 for site 1.4
411.9625 for site 2.1
412.8625 for site 2.1
412.7625 for site 2.2

Can the voice frequencies be determined by these channel numbers?

#### TampaTyron

##### Beep Boop, Beep Boop
There can be 4 different channel plans (where you list a base and step size and bind it to a range of channel numbers) defined OR a "flexible" channel plan where you define every frequency with Tx and rx pair. Remember, most radio programmers are lazy and may be using defaut settngs. Does this band use standard repeater offsets in Canada?TT

#### EricCottrell

##### Member
Using DSD+, I found a system that displays, at the bottom of the Event Log:
TIII (MOT)Site:S2-1.2
TIII (MOT)Site:S2-1.3
TIII (MOT)Site:S2-1.4
TIII (MOT)Site:S2-2.1
TIII (MOT)Site:S2-2.2

In the Channel activity window, it displays channel numbers as follows:
CH 17-18 for site 1.4
CH 7-8 for site 1.2
CH 27-28 for site 2.1

I have identified two frequencies:
410.6625 for site 1.3
412.9375 for site 1.3
412.8125 for site 1.2
412.4375 for site 1.4
411.9625 for site 2.1
412.8625 for site 2.1
412.7625 for site 2.2

Can the voice frequencies be determined by these channel numbers?
Hello,

I am not familiar with how DSDplus treats TIII systems or how Motorola implemented TIII, but your post looks like a jumble of information.

Were you only using DSDplus on the two frequencies you found? What are the two frequencies and how did you get the other listed frequencies?

73 Eric

#### mrscanner2008

##### Member
Hello,

I am not familiar with how DSDplus treats TIII systems or how Motorola implemented TIII, but your post looks like a jumble of information.

Were you only using DSDplus on the two frequencies you found? What are the two frequencies and how did you get the other listed frequencies?

73 Eric
Hi Eric

I'm Using DSD FastLane and my 436 and TRX-1 for finding frequencies.

I found the frequencies by doing a custom search with a tap scanner and DSD and also in my 436hp.
Every time I found a new frequency, DSD show TIII and the site number in the bottom of the Window.

the system is new and didn't have voice call for now.

#### EricCottrell

##### Member
Hi Eric

I'm Using DSD FastLane and my 436 and TRX-1 for finding frequencies.

I found the frequencies by doing a custom search with a tap scanner and DSD and also in my 436hp.
Every time I found a new frequency, DSD show TIII and the site number in the bottom of the Window.

the system is new and didn't have voice call for now.
Hello,

So you are picking up the control channels. That at least give you some site frequencies if the control channel rotates.

There is no direct way to get the channel number of the control channel. DSDPlus may display the Control Channel LCNs on adjacent sites. If it does, then make note of the site numbers and LCNs. Then match up the active control channel frequency with the LCN for each site.

You have to be careful when there is voice on the system as the same transmission can be carried on multiple sites. It is easy to assign a frequency to the wrong site.

73 Eric

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