HELP on scanning Mexico City Police EDACS system

[Auren]

Hello, I recently bought a 246 T scanner from Uniden, and I am trying to scan the mexico EDACS system, buy my problem is determining the LCN order for the channels because there is no follow on replies to users ID. One thing I do notice is the control channel rotates every 12 hours or less, does the rotation of the ctrl channel indicate the LCN order of the next frequency? Thanks I am very frustrated

 

[crayon]

One thing I do notice is the control channel rotates every 12 hours or less, does the rotation of the ctrl channel indicate the LCN order of the next frequency?

I would say yes, that is an indication of LCN. How many frequencies are there total in the system and of those how many does the control channel rotate through?

 

[Auren]

The frequencies where the control channel rotates through have been the following: 866.350, 866.850, 867.350, 867.875, 867.900, 868.100, 868.375. But I have only one week investigating and I am sure there are more. because there are lots of voice channels active starting at 851.250mhz till 868.850mhz. They all are EDACS and they seem to be used by police. I am looking for the data channel of the other systems otherwise this system will be over 40 channels long. I think each county has its own EDACS trunking system, otherwise it will be to much channels. So I will suppose the channels for this system are indicated by the control channel rotation. If there is a frequency where the control channel hasn´t rotated, does it mean the channel is not part of the system?

 

[crayon]

If there is a frequency where the control channel hasn´t rotated, does it mean the channel is not part of the system?

I wish there was a simple correct answer to your question.

Sometimes it will be yes and sometimes it will be no. It all depends on how the trunked system was setup. You have listed the control channel frequencies in an asending numerical order, is this the correct rotation?

You really need to find a way to run etrunker to help with the discovery of these EDACS systems. Is the 245T the only scanner you own?

 

[Auren]

You really need to find a way to run etrunker to help with the discovery of these EDACS systems. Is the 245T the only scanner you own?

Yes its the only trunking scanner I own, I hava a radio shack trunk tracking scanner but its the first generation and it doesnt have EDACS. I am unfamiliar with the term "e-trunker" is that a software or something? Is there an alternative to discover the lCN order of channels?

 

[rickey456]

Auren

Do you have the BC 246T or 245. The 245 will do EDACS. In any event- if you have 2 scanners here are two files I've been saving about how to determine LCN. It takes a bit of work but maybe you can work it out:

---------------------------------------------------------------------------------
file #1

Third hint, this one will allow you to easily figure out LCNs for Edacs
systems. Edacs systems can use up to 25 LCNs. The 245xlt doesn't
seem to be concerned with the current LCN slot for the active
Data-Channel, so put the currently active Data Channel into one of
the last five channels in the Trunk Bank. I recommend the last one, if
its blank. Now switch up to LCN1. Get another 800Mhz scanner, and
get an accurate list of frequencies for the system in-question ; This is
very important. Starting with the first frequency, put it into your 245xlt
into LCN1 & into your other 800Mhz scanner, now press the 'SEARCH'
key to acquire the Data-channel. Listen to both scanners. If both
scanners don't mirror the same audio at the same times, then zero-out
LCN1, and put that frequency into LCN2, and try again. Use this
proceedure til you have them all. You should only have one LCN left,
the LCN for the Data-Channel. If you have more than one LCN left,
then its possible that the extra LCN is disabled because its been
reallocated or the repeater might be in the-shop for service. To figure
out which of the remaining LCNs belong to the currently active Data-
Channel, wait for it to switch the Data-Channel over to another repeater.
Then, program the previous Data-Channel's frequency into one of the
empty LCN slots of your 245xlt & the other 800Mhz scanner.
If both scanners don't mirror the same audio, then try one of the other
empty LCN slots until you get it. This proceedure might take sometime
to complete. It is the, 'Process Of Elimination'. Its the best way to get
it figured out.
--------------------------------------------------------------------------------

File #2


Using this system as an example

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.
---------------------------------------------------------------------------------


Rickey Stein

 

[rickey456]

I went back to some old files from the mid 90's. I'm sure that this has all changed but from these files you are going to have to spend some time because even then, the Cd. Mex. Police were using a number of systems. E-trunk is a great piece of siftware but you have to have the discriminator of the radio tapped.

Here's what I had from the files:
Policia de La Cd. de México D.F.

Sistema "A"
851.5750 852.5750 852.8250 853.5750 853.8250

Sistema "B"
856.0250 857.0250 ------unk-- 860.0250

Sistema "C"
856.2750 856.5250 857.2750 857.5250 858.2750 858.5250
859.2750 ---unk--- 860.2750 860.5250

Sistema "D"
856.7750 ---unk--- 858.7750 ---unk---- 860.7750


y también tiene- [quizá Pol. Edo. de Méx. EDACS Trunk]
851.7500 852.7500 853.7500 854.7500


Rickey Stein

 

[Auren]

Thank you very much, I have the new 246 T with close capture, this scanner doesnt use banks, its another system. But I will give it a try.

 

[Auren]

I went back to some old files from the mid 90's. I'm sure that this has all changed but from these files you are going to have to spend some time because even then, the Cd. Mex. Police were using a number of systems. E-trunk is a great piece of siftware but you have to have the discriminator of the radio tapped.

Here's what I had from the files:
Policia de La Cd. de México D.F.

Sistema "A"
851.5750 852.5750 852.8250 853.5750 853.8250

Sistema "B"
856.0250 857.0250 ------unk-- 860.0250

Sistema "C"
856.2750 856.5250 857.2750 857.5250 858.2750 858.5250
859.2750 ---unk--- 860.2750 860.5250

Sistema "D"
856.7750 ---unk--- 858.7750 ---unk---- 860.7750


y también tiene- [quizá Pol. Edo. de Méx. EDACS Trunk]
851.7500 852.7500 853.7500 854.7500


Rickey Stein

That is great! information!!!! I am definetly going to look into it, do you know where to get more in this info? I have noticed there are more systems then, that are now in the 860´s range. What does --unk-- mean?

 

[rickey456]

unk means that the frequency in the next LCN position was unknown.

There are a number of people who are scanning in Mexico but over the past 30+ years I was able to make contact with only a handful of them when I was the International Editor for RCMA. With that, very few were willing to share their information. I have a 30+ year long friendship with the fellow was always willing to share his information with me. He gave me this info and he is a member here and still helps me with information. I do not know of any other site for Mexican frequency info. There was a fellow in Cd. Méx. who had a website up for a while. I think his site has been down or inactive for almost two years. I still have the information that was posted there and I can share that with you- not much trunking info. I was also recently in contact with a fellow in Monterrey who was beginning to figure out the systems there but I haven't heard from him in many months.

Yes, I understand that there were quite a number of Moto trunk systems in the 860's and while in Pto. Vallarta I was able to find several LTR systems- so there are probably plenty of these in Cd. Méx. also.

Si quieres, puedes escribirme a rickey456@aol.com directamente- en inglés o español. Un abrazo

Rickey

 

[Auren]

Rickey:

Thank you very much for the info, I think I know of the mexican guy you are talking about, is his name: Gerardo o Ricardo Aviles, in his page there are pictures of ambulances or something and many frequencies, but like you say very few trunk info. I will be writing you soon, I am very interested in exploring the frequencies in my city, thanks