Using Tower locations

marrsfiremedic · #1 (**permalink**) 09-13-2005, 10:05 AM

I am still very new to digital trunk scanning. I hear everyone talk about knowing the locations of the towers in michigan and their frequencies. What do you gain in knowing where they are? Does each tower have a frequency that I can program into my scanner that will get me better reception over just putting in the normal control frequencies and all the secondary ones? Please explain. Thank You.

kb5udf · #2 (**permalink**) 09-13-2005, 01:35 PM

The reason it can be helpful to know locations is that it can enable you to maintain a good receiving signal on the system. The other reason may be to hear the talkgroups you want. On a statewide smartzone/apco system, not all talkgroups will be on all towers all the time (typically), so knowing which frequencies relate to which tower locations helps you 1. hear the system at all, 2. possibly hear talkgroups in the area you want.

Real users of this system with their Moto. gear don't have this issue, since their radio scans a list of control channels picks one and logs on, voila, the channel they are on will be active on the tower site their radio logged onto. Of course as a scanner user you don't logon, but still need a means to get the right control channels into your radio. Their are many different ways to do this and I'm sure alot of posts about it here on RR.com.

In general though, whether I was using real moto gear or a scanner, I find the best reception has come from, deliberately selecting the right frequencies for the tower site I wanted to monitor. Often, more than one tower site will be monitorable at a given location (in many systems), but some will be closer to your location, and have stronger signals. If you set up a radio for control channel only mode be it scanner or Jedi series moto, it tends to logon to the first usable control channel it finds, not neccessarily the strongest or the most local. I used to cup my hands around my moto antenna to force it to return to scanning, and latch onto a stronger repeater site.

seamusg · #3 (**permalink**) 09-13-2005, 04:53 PM

Each tower sends out neighbor towers and their Control Channel for the Mot radios to use.

marrsfiremedic · #4 (**permalink**) 09-13-2005, 04:59 PM

Totally lost. I am still a newbie at this. Would it benefit me to program in not only the frequencies of the system, but also the control channel and frequencies of my closest towers??

UPMan · #5 (**permalink**) 09-13-2005, 05:27 PM

Here is a simplified explanation (still kind of complicated...).

On large statewide systems, each site (antenna location) only handles traffic for units that are within range of and registered to that site. Example: A site in the North of the state rarely carries traffic for groups that are normally in the south of the state. If a south unit "roams" up to the north it automatically registers with the nearest site and south traffic is automatically routed so that it is included on traffic for that site. When the unit returns south, it is no longer registered on that site and so the traffic is not carried.

It is important to know what site is nearest where you are so that you can program the scanner with that site's control channel frequency. You might also choose to limit the talk group channels you program along with that frequency to those that normally are on that site. It is also usually the case that you get the best reception when monitoring the nearest site.

There are several other factors, but digest that...I'm fairly sure that some others will chip in on this, too.

RyltnVFD · #6 (**permalink**) 09-13-2005, 06:05 PM

Quote:

Originally Posted by marrsfiremedic

Totally lost. I am still a newbie at this. Would it benefit me to program in not only the frequencies of the system, but also the control channel and frequencies of my closest towers??

Well, simply put, if you don't program at least the primary control channel of the tower you want to hear, you probably won't hear much. The frequencies other than the control channel don't really have to be programmed.

DewAddict · #7 (**permalink**) 09-13-2005, 06:19 PM

I live in Livingston County and monitor the Livingston county system. So I input the control channel frequencies into the scanner for the closest tower site (antenna location) which happens to be in Howell. Since I travel to Dearborn each day I know that I will be passing by the Northville tower and into the reception area of this tower so I input the control channel frequicies for that tower as well.

Now that I have the control channel frequencies in the scanner it now knows what frequencies to monitor for radio transmissions, but it doesn't know "what" to recieve. That is where the Talkgroup ID's come in. Each Talkgroup ID consist of a certain number agencies that transmit on it. For example, Livingston county Central Dispatch, Fire Dispatch uses Talkgroup ID #2147. Only Fire related transmissions will be heard on that Talkgroup and are broadcast through the tower frequencies that I have input into the scanner earlier. If I input Talkgroup ID #2146 into the scanner I will receive only Livingston county Central Dispatch Police radio traffic.

See, the talkgroups share the same control channel frequencies on a Tower site (i.e. Howell Tower) and are then divided into talkgroups to separate what you "hear"

On a VHF scanner, each frequency usually equals one agency, for example, Fire dispatch used to be 154.010 and all you would hear on that frequency was fire related traffic. Whereas now, the frequencies are assigned talkgroups that share the same frequencies. Think of the frequencies as an apartment bulding, which is shared by many tenants, and think of the talkgroups as each apartment in the building. They share the same building (frequency) but may not have anything to do with one another like the (talkgroups.)

If one apartment becomes empty, that is like removing a talkgroup, meaning you will no longer "hear" any radio traffic for that Talkgroup. And when a new tenant moves in, its like a new Talkgroup ID was added to the scanner and now you may "hear" that agency, since they are sharing the same frequency (i.e. aapartment building)

Hope this helps.

Rob

seamusg · #8 (**permalink**) 09-13-2005, 07:26 PM

Quote:

Originally Posted by UPMan

Here is a simplified explanation (still kind of complicated...).

On large statewide systems, each site (antenna location) only handles traffic for units that are within range of and registered to that site. Example: A site in the North of the state rarely carries traffic for groups that are normally in the south of the state. If a south unit "roams" up to the north it automatically registers with the nearest site and south traffic is automatically routed so that it is included on traffic for that site. When the unit returns south, it is no longer registered on that site and so the traffic is not carried.

It is important to know what site is nearest where you are so that you can program the scanner with that site's control channel frequency. You might also choose to limit the talk group channels you program along with that frequency to those that normally are on that site. It is also usually the case that you get the best reception when monitoring the nearest site.

There are several other factors, but digest that...I'm fairly sure that some others will chip in on this, too.

To the best of my knowledge a frequency does not corespond to a talk group, a frequency is assinged each time a transmission takes place. Limiting can only be done on a site or tower basis
Paul is correct you only want the sites or towers that you can receive with a good signal.
My 796 goes nuts on a bad control channel.

Alpha432 · #9 (**permalink**) 09-13-2005, 11:26 PM

I think I am on the same wavelength as marsfiremedic. If I wanted to scan the Downriver mutual aid system, I will program in the frequencies and talkgroups that corospond with it, which I did and I get pretty much everything. I don't think I am missing a beat. But along with those frequencies do I find the nearest tower and put in that towers control frequency and the "licensed" frequencies that are with that into the same bank as the Downriver system? I found the nearest tower to me, there are actually 2. Flatrock and Detroit. They don't have any of the same frequencies as the downriver system. Let me know. Thanks.

seamusg · #10 (**permalink**) 09-13-2005, 11:41 PM

You ONLY need the Control Channel and the alt not all the freq's for each tower.Talk groups don't belong to a tower - only a group. If that group has a radio on in the area of that tower then that tower will broadcast it..if TG 2192 Shelby PD Disp has a car or radio in he area of the Mt. Clemens tower it will broadcast it, also if it has a car or radio in the area of the Detroit tower it will broadcast it, Smart Zone will broadcast TG transmissions for a radio in its area, even if it comes from the UP.