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 Voice/Control Channel Decoding Software - For discussion of software applications which decode digital voice formats and trunking control channels. Please use the HF Digital Signals forum for anything below 30MHz.

11-03-2016, 5:35 PM
 Member Amateur Radio Join Date: Apr 2001 Location: Coconut Creek, FL Posts: 2,687
TIII systems: voice frequencies from channel numbers?

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.
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Ken
11-03-2016, 8:00 PM
 Moderator---not censor Premium Subscriber Join Date: Jan 2001 Location: Unincorporated Ft. Bend County Posts: 2,998

Wild guess, but I'd try 461.5125...assuming my math is correct.
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11-03-2016, 8:54 PM
 Member Database Admin Amateur Radio Join Date: Nov 2002 Location: Boston, Ma Posts: 1,989

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
11-03-2016, 8:59 PM
 Moderator---not censor Premium Subscriber Join Date: Jan 2001 Location: Unincorporated Ft. Bend County Posts: 2,998

Quote:
 Originally Posted by EricCottrell 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.
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Last edited by KevinC; 11-03-2016 at 9:13 PM..
11-03-2016, 9:24 PM
 Member Amateur Radio Join Date: Apr 2001 Location: Coconut Creek, FL Posts: 2,687

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.
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Ken
11-03-2016, 11:32 PM
 Member Premium Subscriber Join Date: Jul 2014 Posts: 4,096

If we're talking Tier III DMR/MotoTRBO, wouldn't the channel spacing be 12.5KHz? TDMA instead of FDMA and all that...
11-04-2016, 10:09 AM
 Member Database Admin Amateur Radio Join Date: Nov 2002 Location: Boston, Ma Posts: 1,989

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
11-04-2016, 11:11 AM
 Moderator---not censor Premium Subscriber Join Date: Jan 2001 Location: Unincorporated Ft. Bend County Posts: 2,998

Quote:
 Originally Posted by jonwienke 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.
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11-04-2016, 11:13 AM
 Moderator---not censor Premium Subscriber Join Date: Jan 2001 Location: Unincorporated Ft. Bend County Posts: 2,998

Quote:
 Originally Posted by W4KRR 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
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11-04-2016, 1:31 PM
 Member Join Date: Aug 2008 Location: Port St Lucie, Fl Posts: 7
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
11-04-2016, 1:38 PM
 Member Amateur Radio Join Date: Apr 2001 Location: Coconut Creek, FL Posts: 2,687

Quote:
 Originally Posted by KevinC 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.
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Ken
11-04-2016, 1:54 PM
 Moderator---not censor Premium Subscriber Join Date: Jan 2001 Location: Unincorporated Ft. Bend County Posts: 2,998

Quote:
 Originally Posted by W4KRR 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.
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05-19-2017, 1:47 PM
 Member Amateur Radio Join Date: Dec 2002 Location: Wichita Falls, TX Posts: 6,493

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.
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Tom
06-20-2017, 8:32 AM
 Member Join Date: Mar 2005 Posts: 402

Quote:
 Originally Posted by nd5y 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.
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Rgds,
Raccon
06-20-2017, 9:12 AM
 Member Join Date: Feb 2010 Location: Tampa, FL Posts: 313

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