Understanding NexEdge Trunking

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troymail

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I'm monitoring a NXDN trunk system which is part of a network in eastern MA. One site seems to operating as a single frequency trunk as the control channel data is also a voice channel.

Has anyone else seen that sort of activity?
Yes - there is a site on a system in Maryland where when I last looked, only the control channel frequency was active and when the only user talked, they took over that frequency. The CC returned when they were done talking.

Not the same thing but I've monitored another system that used the control channel frequency as a voice overflow when all other frequencies on the system were in use.
 

mmckenna

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Yes - there is a site on a system in Maryland where when I last looked, only the control channel frequency was active and when the only user talked, they took over that frequency. The CC returned when they were done talking.

Not the same thing but I've monitored another system that used the control channel frequency as a voice overflow when all other frequencies on the system were in use.
In Kenwood NexEdge terminology this is known as a "Non-dedicated Control Channel".

It can be used in a single channel trunking system. The channel will function as a control channel until a call is made, then it becomes a traffic channel. Useful for very low traffic sites. As you can guess, when the channel switches from a Control Channel to a Traffic Channel, other radios on that system are not able to hear the control channel signal.

It can also be used on a multi-channel site. If all the traffic channels are in use, you can allow the system to utilize the control channel for traffic.
 

garys

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Thank you. That's very helpful information.

In Kenwood NexEdge terminology this is known as a "Non-dedicated Control Channel".

It can be used in a single channel trunking system. The channel will function as a control channel until a call is made, then it becomes a traffic channel. Useful for very low traffic sites. As you can guess, when the channel switches from a Control Channel to a Traffic Channel, other radios on that system are not able to hear the control channel signal.

It can also be used on a multi-channel site. If all the traffic channels are in use, you can allow the system to utilize the control channel for traffic.
 

garys

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Another question. The Channel numbers seem to go in an ascending order. 201 is lower than 202, which is lower than 203, etc...

Does this necessarily hold for channel numbers above 800? Does 801 have to be a lower frequency than 802? Or are all bets off?
 

EricCottrell

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Another question. The Channel numbers seem to go in an ascending order. 201 is lower than 202, which is lower than 203, etc...

Does this necessarily hold for channel numbers above 800? Does 801 have to be a lower frequency than 802? Or are all bets off?
Hello,

If it is a standard UHF map, then any channel above 800 is a custom channel and can be anything.

73 Eric
 

mmckenna

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As you can guess, when the channel switches from a Control Channel to a Traffic Channel, other radios on that system are not able to hear the control channel signal
This should have said "other radio on that SITE are not able to hear the control channel signal since it's been stopped so the channel can become a traffic channel. Usually the radios will throw an "out of range" message on the screen and beep, if set up that way.
 

garys

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Thanks. That gave me a good hint and I found the voice channel. It's Network 178, which you're familiar with. I have the frequency and Channel number matched.



Hello,

If it is a standard UHF map, then any channel above 800 is a custom channel and can be anything.

73 Eric
 

Dispatcher308

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Hello,

Some more information to help in figuring out the Channel Map.

Standard UHF Map Formulas
For Channels 1 to 400:
Freq = 450 + (( Ch - 1 ) * 0.0125

For Channels 401 to 800:
Freq = 460 + (( Ch - 401 ) * 0.0125

For Channels 801 to 1023
Custom frequency, i.e. T-Band or on a 6.25 KHz step.

What is the frequency for Ch 511?
Freq = 460 + (( 511 - 401 ) * 0.0125 ) = 461.3750

Otherwise each system implements their own channel 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. For example, the frequencies for these three channels where figured out.
472.350 MHz = Ch 377
471.600 MHz = Ch 257
471.350 MHz = Ch 217

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

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

See if the other frequencies fit, they do.
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
This formula makes no sense to me and I do pretty well in math, what gives?
 

u2brent

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They do not work for every system.

What do you not understand? It's basic algebra.

Standard UHF Map Formulas
For Channels 1 to 400:
Freq = 450 + (( Ch - 1 ) * 0.0125)

For Channels 401 to 800:
Freq = 460 + (( Ch - 401 ) * 0.0125)

For Channels 801 to 1023
Custom frequency, i.e. T-Band or on a 6.25 KHz step

You just need to perform the calculations in () first.
 

millam

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What does this mean "Site Beacon Signal"? Its used in all nexedge information I seen.

Mil
 
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