DMR TIII system; control channel doesn't show up in CC Channel activity window

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W4KRR

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I am using FMPA and DSD+ to monitor a DMR TIII system. My DSDPlus.frequencies file contains this:
TIII, 01, 1.4, 7859, 472.85000, 475.85000, 0
TIII, 01, 1.4, 7860, 472.85000, 475.85000, 0
TIII, 01, 1.4, 103, 451.62500, 456.62500, 0
TIII, 01, 1.4, 104, 451.62500, 456.62500, 0
TIII, 01, 1.4, 7871, 472.92500, 475.92500, 0
TIII, 01, 1.4, 7872, 472.92500, 475.92500, 0

The control channel is 472.850.

(Yes, I know I don't need to list the even OTA channel numbers).

It works. But in the Control Channel Activity window, it shows this:
103 451.625
104 451.625
7871 472.925
7872 472.925
? CC

The correct control channel is in the DSDPlus.frequencies file, along with the OTA channel number, so why doesn't it show the control channel?

BTW, given these OTA channel numbers, I wonder if it's possible to calculate a complete channel map.
 

u2brent

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I am using FMPA and DSD+ to monitor a DMR TIII system. My DSDPlus.frequencies file contains this:
TIII, 01, 1.4, 7859, 472.85000, 475.85000, 0
TIII, 01, 1.4, 7860, 472.85000, 475.85000, 0
TIII, 01, 1.4, 103, 451.62500, 456.62500, 0
TIII, 01, 1.4, 104, 451.62500, 456.62500, 0
TIII, 01, 1.4, 7871, 472.92500, 475.92500, 0
TIII, 01, 1.4, 7872, 472.92500, 475.92500, 0

The control channel is 472.850.

(Yes, I know I don't need to list the even OTA channel numbers).

It works. But in the Control Channel Activity window, it shows this:
103 451.625
104 451.625
7871 472.925
7872 472.925
? CC

The correct control channel is in the DSDPlus.frequencies file, along with the OTA channel number, so why doesn't it show the control channel?

BTW, given these OTA channel numbers, I wonder if it's possible to calculate a complete channel map.

Are you picking up traffic? Could it be that DSD+ just needs to continue running until it determines the CC#? Or does this issue persist continually?
 

mtindor

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The CC won't indicate until/unless there is voice traffic on it, at which time it will indicate. The Channel Activity window only indicates on voice calls (group / private) to my knowledge. I'm guessing DSDPlus looks for the LCN of voice calls to populate the frequency information in the Channel Activity window. No voice calls on CC, no Frequency to show up next to CC.
 

W4KRR

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mtindor, apparently that is the issue. There's no voice on the CC, on either slot. The active voice channels are showing up as I would expect.
 

Ubbe

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You can use 6,25KHz as a stepsize for the even channel number. The 104 channel have the base of 451.000Mhz which seems ok.
The 7872 channel calculates to use a base of 423.725MHz which seem to be a totally different system.

Whenever you monitor a TierIII control channel the DSD+ should instantly indicate the system id, the site id and the channel number.
You only get indication of the voice channel numbers when they get active. You should also see a list of adjacent sites and their channel numbers, that the radios need to know to be able to roam over to another site when they drop the connection to this site, that you can use to calculate the CC frequency of those other sites. Round up the channel number to an even number and multiply with 0,00625MHz and add to the base frequency, which must be the same in the whole system.

In the network file in the folder you can set if sites use one or two digit numbers. Maybe you'll need to set that differently than you currently have, if you are 100% sure that all the frequencies you have put in the frequency file belongs to the same system.

/Ubbe
 

W4KRR

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Thanks for that info, Ubbe.
The system is this one: http://www.radioreference.com/apps/db/?sid=10234
DSD+ does report system id, site numbers, neighboring sites, etc. Site 1.4, Sunrise, is the only one active now. The other sites are in testing phase. It seems to work and track properly, and I have noted voice activity on only the 451.625 and 472.925 channels.
I believe the two T-band frequencies will be replaced by frequencies in the 453.xxx and 460.xxx range by the time the system goes fully online.
 

Ubbe

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I beleive a channel cannot inform you what channel number it has, so it will send a "GOTO CH XXXX" when starting a voice call from the CC and the voice channel will send a "GOTO CH YYYY" to send a radio back to the control channel and only then will the CC channel number be known by the activity window.

Using channel numbers from the neighbouring sites CC info and checking that it actually are the correct site number on that frequency will verify that your bandplan are correctly set. The 451.000MHz base frequency for channel 0 seems to be the one to use when it goes live.

It seems that a TierIII system first picks the highest free channel number in a site for a voice call and then works it way down in the channel list.
I've only seen one or two times that the free slot in the control channel frequency have been used in the systems I monitor since a couple of years back.

/Ubbe
 

W4KRR

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I beleive a channel cannot inform you what channel number it has, so it will send a "GOTO CH XXXX" when starting a voice call from the CC and the voice channel will send a "GOTO CH YYYY" to send a radio back to the control channel and only then will the CC channel number be known by the activity window.

Using channel numbers from the neighbouring sites CC info and checking that it actually are the correct site number on that frequency will verify that your bandplan are correctly set. The 451.000MHz base frequency for channel 0 seems to be the one to use when it goes live.

It seems that a TierIII system first picks the highest free channel number in a site for a voice call and then works it way down in the channel list.
I've only seen one or two times that the free slot in the control channel frequency have been used in the systems I monitor since a couple of years back.

/Ubbe

Ubbe, based on the information you provided, this formula works for me in determining the frequency from the OTA channel number:
Take the (odd) OTA channel number provided by DSD+, and subtract 3 from it.
Multiply that by .00625
Add the base frequency, 451.000.
The result is the correct frequency (except in the UHF "T" band).

The question is, why must I subtract 3 from the OTA channel number in order for the formula to work?

I would like to create a formula in Excel so that by entering an OTA number, it will calculate the frequency, OR enter a frequency and get the OTA channel number.
 

Ubbe

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The question is, why must I subtract 3 from the OTA channel number in order for the formula to work?

Because I miscalculated. DSD uses an odd numbering system. It's one channel number for the first time slot and one higher number for the second slot, and for frequency channel zero, the base frequency, it will be called ch1 and ch2 in DSD.

In the actual DMR radio and Unidens scanners the base frequency are channel 0 which cannot be used and first valid channel are 1, which is DSD ch3 and ch4. It's normal that the system admin would like to start with channel 1 at an even frequency, like 451.000MHz.

What it ends up into are:
The B1 cell in an excel sheet could be done like =$A$1*0,00625+450,975 and format the cell to use 4 decimals and enter the channel number in the A1 cell. I haven't seen anything else than 6,25KHz step sizes being used in DMR but if they have selected to use 12,5KHz the 450,975 should be changed to 450,325 but that are easily confirmed by listeningen to any DMR signalling on the calculated frequency. You can easily make a formula in cell D1 to enter a frequency in cell C1 and get the even channel number, and subsctract one to get the odd number, =($C$1-450,975)/0,00625

/Ubbe
 

fwradio

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The reason it never populates is as stated in a previous reply. There is never any voice traffic on the channel. If it is a Hytera system and they are using slot 2 as a GPS data channel, you will never have the frequency for the CC show up.
 

W4KRR

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The reason it never populates is as stated in a previous reply. There is never any voice traffic on the channel. If it is a Hytera system and they are using slot 2 as a GPS data channel, you will never have the frequency for the CC show up.
Got it. I was then trying to determine a way to calculate frequencies and OTA channel numbers. Thanks Ubbe!
 
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