UHF frequency channel numbering scheme for NEXEDGE

W4KRR · Oct 6, 2014

When decoding NEXEDGE48 systems, UHF frequencies are assigned a channel number. Examples:

472.350 = CH 377
471.600 = CH 257
471.350 = CH 217
461.375 = CH 511
464.63125 = CH 865

Some of the numbers seem to have a pattern with regard to channel spacing and assigned numbers; some don't. Is there a listing somewhere? It would seem that UHF and UHF "T" band have their own listings. I tried to create a spreadsheet to figure out the numbering, but the numbers didn't match up to what was being reported in DSD+.

n4yek · Oct 6, 2014

Most likely, an owner of a communications company would assign a channel number to each frequency he was allocated by the FCC, no matter if it was part of a trunk system or not. That way, if he ever did decide to include a particular frequency in a system, he would already have a channel number assigned to it.

EricCottrell · Oct 6, 2014

W4KRR said:
When decoding NEXEDGE48 systems, UHF frequencies are assigned a channel number. Examples:

472.350 = CH 377
471.600 = CH 257
471.350 = CH 217
461.375 = CH 511
464.63125 = CH 865

Some of the numbers seem to have a pattern with regard to channel spacing and assigned numbers; some don't. Is there a listing somewhere? It would seem that UHF and UHF "T" band have their own listings. I tried to create a spreadsheet to figure out the numbering, but the numbers didn't match up to what was being reported in DSD+.

Hello,

I saw mention of a standard UHF Channel map in the product documentation. One of the local UHF system uses it, I document it here.
http://forums.radioreference.com/di...re/298075-understanding-nexedge-trunking.html

Otherwise each system implements their own channel map. I was listening to a wide area NexEdge trunked (Type-C) system up in Montreal with a channel map of over 250 frequencies. The map did not seem to follow any pattern but I did not receive many frequencies.

Standard UHF Map Formulas
For Channels 1 to 400:
Freq = 450 + (( Ch - 1 ) * 0.125

For Channels 401 to 800:
Freq = 460 + (( Ch - 401 ) * 0.125

In your case the system using Channels 511 and 865 is likely using the standard UHF map.
461.3750 = 460 + (( 511 - 401 ) * 0.125 )
464.63125 is a 6.25 KHz step frequency so it is in the custom part of the standard map.

After getting a few frequencies on the system, you can try the same techniques used to get the frequency mapping of a Motorola Analog VHF/UHF system.

( 471.600 - 471.350 ) / ( 257 - 217 ) = 0.00625 KHz (reasonable step size).

Base (Ch 1) = 471.350 - (( 217 - 1 ) * 0.00625) = 470.000

471.6000 = 470.000 + (( 257 - 1 ) * 0.00625)
472.3500 = 470.000 + (( 377 - 1 ) * 0.00625)

So the system has a Base (Ch 1) of 470.000 MHz with a 6.25 KHz step size. I do not know if the mapping is always divided into three parts (1 - 400, 401 - 800, 801 - 1023).

73 Eric

WayneH · Oct 6, 2014

I'm not seeing a standard. For example:

454.33750 NE4 3
454.36250 NE4 4
454.24375 NE4 266
454.25000 NE4 267
454.25625 NE4 268
454.26250 NE4 269
454.26875 NE4 270
454.35625 NE4 284
454.32500 NE4 353
454.35000 NE4 355

These are from the same system.

On a different system, though Narrow format, I see 3 and 4 assigned backwards as 452.2125 and 451.9875 respectively.

When I have seen T-band (480MHz) I've seen Chs above 801 (Very Narrow) and yet Ch 26 used for 484.02500 for a Narrow system.

n4yek · Oct 7, 2014

Eric,
You showed me that a couple of weeks ago (and forgot you did) ....but the local system i monitor does not follow your example you say is standard.
The local system base freq is 453.59375, does this mean the company can set it to what ever they want?

EricCottrell · Oct 7, 2014

n4yek said:
Eric,
You showed me that a couple of weeks ago (and forgot you did) ....but the local system i monitor does not follow your example you say is standard.
The local system base freq is 453.59375, does this mean the company can set it to what ever they want?

Hello,

From what I have seen, yes.

There is a standard UHF map that systems may use for UHF as I have outlined. Otherwise a custom map is used. A custom map has to be used for VHF and other bands.

I have not gotten an oppotunity to look at how the frequencies on a system are programmed, as Kenwood has really locked things down and there is not even helpful youtube videos.

From what I have seen so far...

The system manager uses special software with a system key to generate the site and frequency infomation. This information is programmed into all the radios in the system.

The system manager can use the standard UHF map and add any custom frequencies in channels 801 to 1023 for an UHF system. A local UHF NXDN48 system does this. 420 MHz UHF systems need a custom map.

The system manager can create a custom map and manually enter up to 1023 frequencies. I have seen a couple of system where this seems to be the case with upwards of 300 frequencies.

The system manager may be able to use a macro function in the software to generate the custom map. Entering a base frequency, a frequency step, and a channel range results in the channel range being populated with frequencies. I have seen several systems where this seems to be the case.

Monitors mapping out NexEdge Trunked (Type-C) systems have to assume the worse case, a custom map of unrelated frequencies. You have to wait until activity on the control channel and see what channel comes up. Easier to do when you use a Icom R2500.

73 Eric

slicerwizard · Oct 7, 2014

W4KRR said:
When decoding NEXEDGE48 systems, UHF frequencies are assigned a channel number. Examples:

472.350 = CH 377
471.600 = CH 257
471.350 = CH 217
461.375 = CH 511
464.63125 = CH 865

Some of the numbers seem to have a pattern with regard to channel spacing and assigned numbers; some don't..

In many cases, you need to take the current control channel frequency and look up its IC/FCC license and then use that info to look up the rest of the site frequencies. Load them into a scanner and see which frequency lights up when the control channel shows voice activity. Same deal as LTR and EDACS LCN tracking.

jazzbassNick · Oct 13, 2014

slicerwizard said:
In many cases, you need to take the current control channel frequency and look up its IC/FCC license and then use that info to look up the rest of the site frequencies. Load them into a scanner and see which frequency lights up when the control channel shows voice activity. Same deal as LTR and EDACS LCN tracking.

I found a NEXEDGE48 control channel along with a couple of nearby voice frequencies, but when I tried to locate them in the FCC db, they show up as part of a range licensed to an owner (not to be named, since they caused trouble for RR in the past) as paging frequencies.

Since the 454.xx freqs I did find are allocated as part of a block on WPVE963, I suppose any chance of tracking other freqs by the same owner in ULS may prove fruitless.

So is it legit that they are using freqs licensed for paging for a a NEXEDGE system instead?

FYI - Any SoCal folks wanna play, this is what I found:

Code:

[B]CH        Freq[/B]
361       454.49100
367       454.49750 (CC)
382       454.590400

n4yek · Oct 13, 2014

jazzbassNick said:
So is it legit that they are using freqs licensed for paging for a a NEXEDGE system instead?

Yes, see the second paragraph
Part 22 Paging Channels - The RadioReference Wiki

jazzbassNick · Oct 13, 2014

Much obliged @n4yek. That wiki page has some potentially useful info too

jazzbassNick · Oct 14, 2014

Just an observation, when the radio has same NID, but different RAN, there's no correlation between channel number and freq.

I had an RID that was showing on both the CC and Voice channel (my second RTL stick was parked on the VC), but every time it came up, the CC indicated a different channel number.

Monitoring the second site's CC, the freq I was monitoring for voice came up consistently with the same channel number. I'm assuming that's how linked sites are supposed to work?

EricCottrell · Oct 14, 2014

Hello,

RAN is only applicable to Conventional systems. The field is reused on NexEdge trunk systems for the site number modulus 64. A value of zero is site 64, not a wildcard value to listen to everything. The second control channel should have the same value as the VC you were monitoring.

In your case there is a talkgroup transmitting on at least two sites. The control channel on the two sites will show the same talkgroup and radio ID with each showing the channel number at the site carrying the traffic. There is another VC associated with the first control channel carrying the traffic.

So you need to match up the site number between the control channel and voice channel as well as the talkgroup and radio id.

73 Eric

jazzbassNick · Oct 15, 2014

Thanks Eric. That helps!

UHF frequency channel numbering scheme for NEXEDGE

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