Need help understanding file structure

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paulmohr

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Ok, I am playing around with my 325p2 and Freescan software. I think I have grasp on the conventional system, but the trunking part has me a bit confused.

First let explain how I "think" it works then someone can correct me if I am not understanding right.

Systems - This would be the particular trunking system you want to monitor, for instance in my area there is:

the State public safety system (MPSCS) on P25 phase I,

The railroad which is on an NXDN system

ComSource is on DMR TRBO

Consumer Energy is on EDACS standard

The county road commission is on an LTR passport system

And the MIdport Electronics is on LTR standard.

So if I wanted to listen to the county law enforcement, EMS and State Police I would use the MPSCS P25 system. If I wanted to listen to the railroad I would use the NXDN system (if I had a TRX-2 that could pick it up).


Sites - Are pretty much just that, the actual site that is associated with the antenna or antennas for that system in a specific area. For my MSPC system I have numerous sites around me, Adrian, Monroe, Jackson and Detroit (there are others as well).

What I would optimally want to do is choose the site ( ie antenna location) closest to me. In m case it would be Adrian. If I wanted to choose a different site I would have be either close enough to receive it, or have an antenna strong enough to pick it up from where I am. As in it does me no good to choose the Detroit site unless I am going to actually be in that area or I have a really good antenna that can reach 50 miles.

Groups - These would be the specific cities, counties or agencies associated with the system. For instance for me it would be the different county sheriffs offices, any city systems on that network and the State Police.

Here is where my confusion starts. I am using a large tv tower antenna hooked to my scanner. I was told it probably wouldn't work, but it does. At least better than the rubber ducky or the OFCD home brew I made yesterday. (granted I can't get the the home made antenna as high, I am scared of heights and I am not climbing that tower lol). It is pretty directional, but I have a rotor adjustment for it. I can pick up regular signals 150.00 to 450.00 from almost 50 miles away if I point it in the right direction. It is a no go on the Apco25 systems unless they are very close (my home town). I am going to assume this antenna just blows at picking up 800.00 signals. Which is probably why I was told it wouldn't work very well.

If I choose the Monroe or detriot sites I pick up nothing, it is just dead silence on the trunked systems. Now if I choose the local Adrian site I can pick up Lenawee county groups, monroe groups like those county sheriffs and that state police post in Monroe. And I can pick up conversations from cars pretty far away (over 20 miles away).

What I can't get state police from jackson or detriot. I know there is a ton of highway patrol traffic outside of detriot, but I don't hear any of it. Just the local adrian and monroe post. Is this because the local Adrian tower can't pick them up either, so if it can't hear them, neither can I?

And if this is the case, does that mean that if I programed in the sites for monroe, jackson and detriot that I would start to receive them if drove closer to that area, or had a better antenna that could reach that far?

An example would be if I created a system for the State Police and linked it to the michgan state public network (apco25 phase I). Then added the sites for Adrian, Monroe, Jackson and Detroit. Then added all the State Police groups in those areas. Would that mean that as I drove around and left one area, then entered the other it would start receiving transmissions from those towers because I was in range now. Or same thing with a better antenna pointed in the direction of those particular sites.

Am I close to understanding this or am I hopelessly lost? Back when I had a regular scanner you were either close enough to pick up that frequency or you were not. I kind of assumed that if I could pick up one site from the network I could get the whole network. I am either wrong about that theory, or I just can't program those other areas correctly and it isn't picking them up.

Let me clarify that a bit. I thought since all the state police were on the mighigan public system, that if I could pick up one site (adrian) that I could listen to whatever group I programmed in, even if it was on the other side of the state. Simply because it was the same system and they were all linked. Now I am thinking that is not the case and instead you need to able to receive signals from a site closer to those groups in that particular area.

So that would mean that the Detroit area state police cannot communicate with cars or posts in the adrian area if they are physically in the detriot area ( out of range). So they would either need to be closer to my area, start communicating with the local post (14 in monroe) or they have much more powerful systems in their cars than what my little scanner has.

Does this make sense to anyone, or did I just take too much anxiety medication today lol.
 
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jonwienke

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On large trunked systems, most talkgroups are NOT broadcast from all sites. Houghton Lake doesn't want/need to get spammed with all of the traffic from Detroit. System designers determine which site(s) need to broadcast a talkgroup for that talkgroup to function, and it is not carried by other sites. A talkgroup will often be carried by more than one site so that coverage gaps are eliminated, but only a select few are carried system-wide.

Some talkgroups allow roaming--a site outside the "home" area will carry a talkgroup when a user for that talkgroup affiliates with an out-of-area site, but it is normally not carried. This is used for mobile teams like the governor's security detail--they don't need to spam every site in the system with their traffic, but they need to be able to operate statewide.
 

marksmith

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I think you have a fair take on things.

Generally, on statewide systems, it is very rare that one side of the state can talk to the other side, except in special circumstances. Typically, trunked p25 sites require that the transmitting radio be authorized on the particular sites it uses. That way, things are generally in their operating area. Those things capable of statewide operation generally only activate the sites around them. There might be a special talkgroup for cross-state types of special things, that's mainly inactive.

A TV antenna on a mast can usually do ok, mainly just do to height. However, they tend to be somewhat directional, and that could be part of your problem with some things you might have expected to receive.

Keep in mind that 800mz signals are not long range like vhf or even uhf. A signal from a site more than 30 miles away will be difficult, depending on terrain, etc. P25 systems are also directionally set up to stay within their operating jurisdiction and not be received (or interfere with) adjacent jurisdictions. So if you are not in some of these areas you are trying to receive, that's a likely cause.

I am sitting less than a mile from an adjacent county's p25 system, but can't hear it for two reasons.

1. It is designed directionally not to reach my county, even though only a mile away. It is beamed away from my county so as to not reach here.

2. It is a simulcast system. If only the one tower on the system were near me, I could receive it just fine. Unfortunately I am between 2 towers, both operating the same frequencies. This produces something called simulcast distortion where these signals interfere with each other as the scanner tries to receive. Scanners are not made to handle this phenomenon, while you would think signals coming ftom 2 towers would make it stronger. Doing things like attenuation or directional antennas to get only 1 tower can help, but not solve this problem. Note- I can drive through the issue county and receive it just fine while mobile, but not from my house. A mile down the road, comes in fine.

The majority of what you relayed is accurate. There are just a few new things, mainly with digital trunked systems, that have changed in the past 5 or 6 years.

You might also want to check what you are trying to receive in the online database. Digital systems, in particular, may have some or all of their talkgroups encrypted. The 325 p2 will ignore phase 1 encryption and squalk noise with phase 2 encryption.

536/436/ws1095/996p2/996xt/325p2/396xt/psr800/396t/HP-1/HP-2 & others
 
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paulmohr

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Ok, that makes sense. Thanks a lot. So I am kind of close to understanding the basics then.

So what I could do is program in systems for certain areas and when I travel to that area I can just switch to that system. Or I guess just let it can all of them even if they are not in range.

And if I want to hear Detroit area highway patrol I am simply going to need a better antenna system than I have now.

It makes more sense the way you explained it. There is an actual purpose to breaking up the different regions in order to reduce radio traffic in that area.
 

paulmohr

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Ok, with both your explanations it makes way more sense now. And the guy did tell me I live inbetween 4 tower sites so that might be an issue for me. That is why he said the little stock antenna would probably work just fine.

So getting a big huge expensive antenna probably won't help me get Detroit area highway patrol if it is specifically designed not to bleed over into my county. That tid bit of information helps me a lot lol. I would have been pretty upset had I overcome my fear of heights, climbed up that tower and installed a new 300 dollar antenna. Just to find I still couldn't get what I was trying to get lol. But if I was in that area I could pick up the traffic.

And I don't actually plan on driving around with my scanner on. My mom is getting old and has dementia so I stay here to keep an eye on her. And I do almost the driving taking her around. I would probably use the scanner to listen to stuff while sitting in the car waiting for her to do whatever. It is not uncommon for me to drive her 80 miles away to a Good Will store in Canton michigan if she decides that is what she wants to do that day.
 

ofd8001

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Large statewide trunked radio systems are much different these days. The intent is to get as many local users on systems for interoperability purposes.

A whole new line of thinking comes into play. "Old" systems would have a couple dozen "blow-torch" transmitting sites with several hundred watts of effective radiated power. The new trunked systems have, in Michigan's case, about 200 sites with lower power. (Also 100 watts of 800 Mhz signal won't go as far as 100 watts of 30-50 Mhz signal).

Thus the "foot print" of each site is smaller. All sites are linked together through zone controllers so that when a need arises, sites can be linked so as to achieve a very large coverage area.

As Jon noted, not every site carries every transmssion routinely. There's no reason for day to day things going on up north to be carried down south.

The typical expectation would be to receive sites only within 30 miles, though in your case the taller tower extends that a bit. Your antenna cable is a factor too. If you get cheap cable, there will be more line loss than with more costly stuff like LMR 400.

The bottom line is statewide trunked radio systems is a whole new ballgame. They are very elaborate things too.
 

ofd8001

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There were some responses as I was writing mine. At least we're singing the same song.

So what I could do is program in systems for certain areas and when I travel to that area I can just switch to that system. Or I guess just let it can all of them even if they are not in range.

And if I want to hear Detroit area highway patrol I am simply going to need a better antenna system than I have now.
It's more efficient to attempt to receive just those sites within about 30 miles. Programming all sites slows down scanning. If there are 200 sites and each has 5 possible control channel frequencies, that's like trying to scan 1,000 conventional frequencies time-wise.

I didn't catch how far away you are from Detroit. If you are 50 miles, have a tall antenna and use low loss cable, you might. Terrain is a factor and whether there are tall buildings between you and the transmitter sites.

(You may ask this question in the Michigan forum where folks with more specific knowledge about the system might chime in).
 

paulmohr

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speaking of driving with a scanner in your car. From what I could tell on the internet is Legal to have a scanner in your car. You just can't use it to commit a crime or evade capture. I mentioned that in the store and the guy laughed at me. He said the internet is wrong and it is illegal to have a scanner in your car in Michigan. He said he use to be a deputy. And since this shop services police cruisers there were a couple officers there too. The both said the same thing. If you get pulled over and we see or hear that scanner you will get a citation and we will confiscate it. If you want to argue the legalities of it you are more than welcome to do it in court when you go.

So the scanner will be off and in the glove compartment when I am driving lol.
 

paulmohr

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Ya, I live about 45-50 miles from the detriot area. Give or take, it is a huge area. And it isn't a deal breaker either. It is just interesting to listen to the highway patrol in that area in bad weather, lots of wrecks an stuff. There used to be a feed for it on broadcastify but it went down.

And yes, my feed line is garbage. It is probably 10 plus years old and I am sure it was not high quality cable to begin with. Was here already when we bought the house. And I am not gong to climb that antenna and swap it out either. Now if someone came with a boom truck and bucket I would be happy to, but I am not hanging off that thing like a monkey lol. I could mount the OFCD I made upstairs though and run some decent feed line to the basement if I felt ambitious. However I took the scanner up there with the antenna yesterday it didn't seem like a huge improvement over having it in the basement hanging from the ceiling. Then again I have no way to test it either. Other than the fact that it didn't pick anything extra up, nor did the transmissions sound better while I was up there.

I have noticed some channels are much louder than others, I thought maybe it was a reception issue, but I don't think so now. Maybe more to do with their set up, or how the person is using the mic. I just use the volume offset function to try to equal it out. Kind of surprised there isn't an auto function for that like on tv's and media receivers.
 

jonwienke

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And I don't actually plan on driving around with my scanner on. My mom is getting old and has dementia so I stay here to keep an eye on her. And I do almost the driving taking her around. I would probably use the scanner to listen to stuff while sitting in the car waiting for her to do whatever. It is not uncommon for me to drive her 80 miles away to a Good Will store in Canton michigan if she decides that is what she wants to do that day.
Even if you don't turn on the scanner until you arrive at your destination, you would still greatly benefit from connecting a GPS to your scanner, or installing one internally. That will enable the scanner to automatically toggle sites and channels on and off so that it isn't wasting time scanning stuff completely out of range. Location Control is a lot more precise and user friendly way to do that than trying to manually toggle stuff on and off, especially while driving. Having a GPS connected to the scanner makes it practical to use while driving. You can just drive and listen, rather than constantly having to fiddle with buttons.
 

marksmith

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Having poor cable to your big TV antenna means the standard antenna on the radio is probably better than the big high TV antenna.

Especially at 800mz, the signal loss is probably worse than the gain of the antenna.



536/436/ws1095/996p2/996xt/325p2/396xt/psr800/396t/HP-1/HP-2 & others
 

paulmohr

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The big antenna is definitely better the little stock one on 15x.xxx. I picked up Henry county police in ohio which is 50 miles away. However you right about 800mz, it sucks lol.

I am experimenting with placement of my home made dipole now. I strapped it to a chimney right outside my basement entrance door. Its about 6 feet up (didn't want to get the ladder out lol) with a new 25 ft feed line. Its just running out the door for now. Seems to be working pretty good. I picked up Saline which at least 20 miles from me. That is more than enough range for what I need at the moment. I may move it up higher later and attach it better.

I am surprised at how well that little stock antenna works though. It picks up way better than the hand held radio shack scanner I had in the late 90's. Hand held lol, that thing was bigger than most mobile base units are now.
 

marksmith

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The big antenna is definitely better the little stock one on 15x.xxx. I picked up Henry county police in ohio which is 50 miles away. However you right about 800mz, it sucks lol.

I am experimenting with placement of my home made dipole now. I strapped it to a chimney right outside my basement entrance door. Its about 6 feet up (didn't want to get the ladder out lol) with a new 25 ft feed line. Its just running out the door for now. Seems to be working pretty good. I picked up Saline which at least 20 miles from me. That is more than enough range for what I need at the moment. I may move it up higher later and attach it better.

I am surprised at how well that little stock antenna works though. It picks up way better than the hand held radio shack scanner I had in the late 90's. Hand held lol, that thing was bigger than most mobile base units are now.
The stock antenna is surprisingly good. Have used other well known good ones on the radio, and for 800mz it's hard to beat.

Just getting an antenna outside can often help depending on your insulation types, etc.

536/436/ws1095/996p2/996xt/325p2/396xt/psr800/396t/HP-1/HP-2 & others
 
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