[TrunkCom] Determining EDACS Logical Channel Order

[Brian J Cathcart]

On Sat, 1 Jun 2002 21:47:29 -0700 "Justin W. Pauler"
<justin@jwpauler.org> writes:
> These are the frequencies that are in use, in the exact order they 
> are shown in the FCC database (which sorts them, I know) and on
> trunkedradio.net:
> 
>         935.1375
>         937.6750 <CONTROL CHANNEL>
>         938.9000
>         939.4125
>         939.9125

For EDACS systems, the easiest way to determine LCN is to put the control
channel in a higher channel in the bank, then enter each voice frequency
into every channel until you nail which LCN it is in.

For example: use Bank 1 for this EDACS system, which has 5 frequencies. 
Place the control channel (937.675) into channel 6 or higher (why?
Because you are trying to determine LCN order, you do not want to take
the chance of putting the control channel into a voice LCN).  The scanner
does not care what channel the control channel is in, only the voice
channels (and make sure you enter them in trunking mode).  Now, place
935.1375 into channel 1, 2, 3, 4, and 5 and begin tracking the system. 
As soon as a talkgroup with voice activity pops up on the scanner, exit
trunking mode, and the scanner will be on one of these channels, which
will be the correct LCN (i.e. let's suppose for this example that the
scanner is on channel 2 as soon as you exit trunking mode, you know that
935.1375 is LCN 2).  Now repeat these steps for the next frequency
938.900, but this time enter it into channels 1, 3, 4, and 5, and enter
"0" into 2 (again, for example we are assuming we already found LCN 2). 
Enter trunking mode again, and when a talkgroup pops up again, exit
trunking mode and note which channel the activity was on.  Continue this
process until you determine the LCN for all of the frequencies, and by
process of elimination you will find the correct order of the voice
channels.  The control channel, however, you will not know which LCN it
is until it changes to another frequency and you repeat the process.

VERY IMPORTANT - this method assumes the system is using sequential
LCN's, i.e.

LCN1
LCN2... all the way to
LCN5

BUT some systems will "skip" LCN numbers, i.e.:

LCN1
LCN4
LCN5
LCN7
LCN9

In other words, they could use the 5 voice frequencies you listed above
but give them non-sequential LCN numbers.  If your system is like this, I
would then place the control channel into channel 26 (since EDACS systems
have a limit of either 20 or 25 channels) and do the procedure I listed
above, but enter the voice frequency into maybe 10 channels at a time.

The best way is to run ETRUNK on the system to see which LCN numbers
exist on the system, then use the above method to determine which
frequencies pair up to each LCN.

--

The Scanner Dude
Brian J. Cathcart - KE4PMJ
South Florida Frequency & Trunking Guide - 6th Edition (On CD-ROM too!)