ARMER system usage

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blue5011

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Are transmissions on the MN ARMER system car-tower-car or car-to-car (simplex)?

In other words, is it possible to hear a direct call (from) a State Patrol Car, County Sheriff, or EMS? Or do I hear it after it is repeated by a tower site?

Also, since my local LEC (Faribault County) hosts the Blue Earth ARMER tower, is the LEC dispatch access by wire, Internet, or radio? Could it be all three?
 

sjgostovich

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I'm no expert- but:
1- The only simplex channels are the "Scene of Action" channels (that i'm aware of).
2- It might be, but you would have to be close and in a "search mode" within 800mhz on your scanner.
3- I think it varies by where you are as to how dispatch accesses the main tower.

I'll defer to those who know more as to how the ARMER system works. They could provide you with much more info on it.
 

sfd119

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Are transmissions on the MN ARMER system car-tower-car or car-to-car (simplex)?

In other words, is it possible to hear a direct call (from) a State Patrol Car, County Sheriff, or EMS? Or do I hear it after it is repeated by a tower site?

Also, since my local LEC (Faribault County) hosts the Blue Earth ARMER tower, is the LEC dispatch access by wire, Internet, or radio? Could it be all three?
If it's an ARMER transmission, there are no "car to car" simplex channels. There may be a Car to Car TG, but that still goes through the system.

Trunking System = No Simplex (unless you change zones to a simplex channel, but then you wouldn't be on the trunking system).
 

SCPD

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Yep, any talk groups on AMRER go through the system sort of speak. It's not like the old days when car-car comms were simplex, but they had 100w radios in them so range was fine. You cold program the input freqs from the system in a bank and scan it. What is heard are units that are very close to your receiving location. Kind of gives a idea of who is in the area.
 

blue5011

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If it's an ARMER transmission, there are no "car to car" simplex channels. There may be a Car to Car TG, but that still goes through the system.

Trunking System = No Simplex (unless you change zones to a simplex channel, but then you wouldn't be on the trunking system).
I got the C2C talkgroup concept. What I am curious about is the actual radio transmission "as the mike button is pressed".

So an accident happens on the highway in front of my house. PD/ Fire/ EMS respond, and I would not be able to hear the conversation from said vehicle "as it is being transmitted" to the tower/ system?

Is there a backup/ default mode the vehicle radio would go in to if all the local towers fail?
 

NDRADIONUT

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You can listen to the site input voice freqs which are 45 mhz lower than the outputs... 851.0125 = 806.0125 etc

Wont be any talkgroup following though...
 

ScanWI

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Is there a backup/ default mode the vehicle radio would go in to if all the local towers fail?
These is a mode called Failsoft, this is a option programed into the radio, however large systems like ARMER do not use it. If the system goes down you are limited to the channels in your radio that are not on the system.

This is the problem with having a central controller on a large trunking system, it makes the system more vulnerable.


A Trunking site is comprised of two or more repeaters, in P25 trunking one of those repeaters is constantly transmitting Data, this is known as the Control Channel. The other repeaters are shared between different users, to handle more traffic.

The radio is always watching the Control channel, when there is no traffic the radio is sitting on that channel. When a operator pushes the PTT the radio first transmits on the control channel give the system it's Radio ID, Talkgroup, and type of call. The system tells the radio through the control channel which repeater on the tower to use, and any other radio monitoring that talkgroup to listen to the same repeater.

Here is a good Explanation of Trunking if you have any more questions
http://wiki.radioreference.com/images/c/c7/Trunking_description.pdf
 
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I got the C2C talkgroup concept. What I am curious about is the actual radio transmission "as the mike button is pressed".

So an accident happens on the highway in front of my house. PD/ Fire/ EMS respond, and I would not be able to hear the conversation from said vehicle "as it is being transmitted" to the tower/ system?

Is there a backup/ default mode the vehicle radio would go in to if all the local towers fail?
I think perhaps this has already been answered, but...

All communications on ARMER are through a repeater. That being said, I suppose you could tune a scanner to the repeater input frequencies of a site and catch the audio that way. You might catch the transmission as it is leaving the end user radio on its way to the repeater. You wouldn't be able to track the conversation as it may hop around to different freq's anytime the PTT is pushed. You would also have to be pretty close to the transmitting unit as the power level is lower than many of the old 100 watt VHF mobile radios.

For your question of a "back-up" system...yes and no. Failsoft is a site failure and you can set up radios that will use one of the channels on the site as a conventional repeated radio frequency. This was not an option on simulcast sites, but I heard that with the most recent ARMER upgrade, or perhaps the next upgrade, it will be an option on Simulcast sites as well.
 

SCPD

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There will eventually be a transition to Phase II but it's a while down the road. As radios reach their the EOL they are being replaced with Phase II compatible ones. The PSAP's are in the process as well with their consoles. I was told by Hennepin radio the channel capacity was fine at the present time. Hopefully by the time Phase II hits ARMER, the scanner makers will have the simulcast receiving issues somewhat fixed.
 

blue5011

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Part of the reason I asked these questions is a eHam seller had some Moto radio's capable of P25 800mhz for $40. I asked what can you do w/ those? The reply was to monitor the control channels in "conventional" mode, but using software to "read" or decipher the transmission w/ a trunking software program. I then asked IF the radio would follow a conversation. The answer was IF it is from one tower, that the radio has all the "talk" channels in, listed in "conventional" mode.

Does any of this make sense?

All this being said, IF I had a P25 800mhz capable radio, w/ all the Blue Earth tower "talk" channels in it I should be able to see who is on the system, because the BE ARMER tower is on the same site as the Faribault County LEC.
 

sfd119

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Yes, it makes sense. Think of it like this:
RadioFreq#1: Control Channel.
RadioFreq#2: Voice Channel 1
RadioFreq#3: Voice Channel 2
RadioFreq#4: Voice Channel 3
RadioFreq#5: Voice Channel 4
RadioFreq#6: Voice Channel 5
RadioFreq#7: Alt Control Channel.

If you programmed Radio Frequiencies #2-6. you would hear the radio traffic from EVERYBODY. If Squad Car 1 talks on LAW1, it might assign it to RadioFreq#5. If Squad 2 answers, the control channel might carry that traffic to RadioFreq#2. If a Fire Truck AND a Squad car are BOTH talking at the same time..then RadioFreq#3 and RadioFreq#6 might be assigned for their transmissions...but you would only hear what your radio picked up first.

Make sense so far?
 

ScanWI

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Yes you can do this however it will not work as well as a real scanner. You will see the radio ID's and not the Talkgroup ID's and you will hear any other traffic that comes over the voice channels, DPW, Transit, hospital. Police, and fire traffic. If it is in the area on the system you will then hear it.
 

blue5011

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Yes you can do this however it will not work as well as a real scanner. You will see the radio ID's and not the Talkgroup ID's and you will hear any other traffic that comes over the voice channels, DPW, Transit, hospital. Police, and fire traffic.
The eHam seller seemed to imply that since these were "real motorola" P25 800mhz units, that there was "enhanced" listening pleasure! I was about to buy one, until I figured out it would only be good to listen to one site, and I can probably do the same thing w/ my Icom PCR-2500.
 

ScanWI

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The eHam seller seemed to imply that since these were "real motorola" P25 800mhz units, that there was "enhanced" listening pleasure! I was about to buy one, until I figured out it would only be good to listen to one site, and I can probably do the same thing w/ my Icom PCR-2500.
The radios may be capable of P25 trunking, however a trunking radio can only trunk on a system with a valid Radio ID(provided by a system Admin), System Key(provided by System Admin), and system parameters. Without the RID and System key the radio is only capable of conventional operation.

I hope this makes sense, but this is why a scanner will work better for listening to a trunking system.
 

blue5011

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I must not be asking the right question.

The radios may be capable of P25 trunking, however a trunking radio can only trunk on a system with a valid Radio ID(provided by a system Admin), System Key(provided by System Admin), and system parameters. Without the RID and System key the radio is only capable of conventional operation.

I hope this makes sense, but this is why a scanner will work better for listening to a trunking system.
I have read about the affiliation thing and the problems/ desires for some to have the experience of a "real" digital listening pleasure by disabling the transmitter/ final stage. I have no desire to go that route. It is the nature of the signal I must be confused about...

When the eHam seller and you refer to "conventional mode/ operation", does that refer to reception of radio transmission in FM or Digital (P25)? And is there a difference between a P25 Motorola and a non-P25 radio (say a VHF version)?

Or is the reception a simple matter of software, on any radio? The seller referred to using "Trunker" software in order to decode the P25 signal.

Thanks for the replies, I am done flogging this horse, and should probably be reading the Moto forum more often.
 

blue5011

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Took my own advise and re-read the Mot Trunking thread. It was interesting. And since I "didn't" buy any Moto radio, I won't ask anymore questions on that subject.

Although something might need asking as I explore using my PCR-2500 for P25/ digital scanning.

Thanks again for any and all replies.
 

dwgelle

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There is failsoft built in to the ARMER system sites and radios if the worst does happen to a site.
 
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