How Do You Figure Out Frequency's For Racom Talkgroups?

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weevy

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I am still trying to learn about Racom Edacs system. How do you know what freq. is a specific talkgroup. Take for instance Polk County Sheriff's office in Iowa.

Or is their a specific freq.

Any help would be appreciated.
 

ka3jjz

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Trunking doesn't work that way. Put simply, once the sheriff joins the system, he may bounce around on any of the frequencies that are allocated for that system's site.

There are, however, cases where a specific talkgroup might be slaved to a single frequency - typically this is to allow folks that don't have trunking scanners to hear important alerts. For example, in Anne Arundel county, Maryland tg (a common abbreviation for talkgroup) 16 is slaved to 154.01 - this is the fire dispatch frequency. You could have such a setup for a sheriff or police dispatch as well, and for much the same reason.

We have a couple of articles that will help you understand the concepts in our wiki. Read the 2 links (anything in blue is a link) found in the Overview section of;

Trunked Radio Systems - The RadioReference Wiki

and you'll start to see how things work.

best regards..Mike
 

DickH

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I am still trying to learn about Racom Edacs system. How do you know what freq. is a specific talkgroup. Take for instance Polk County Sheriff's office in Iowa.

Or is their a specific freq.

Any help would be appreciated.
First, you need to understand how trunking works. A simple explanation follows.
A quick look at the database shows at least 3 sites (towers) in Polk county; sites 1101,1207 & 1310. You may need to put all of them into your scanner. Someone in the Iowa forum may know .
After the freqs. are entered, then you enter the Talk Groups you want to hear. Scroll down to Polk Sheriff for a list of TGs.

T R U N K I N G
Motorola Trunking: (EDACS explained at the end).
The object of trunking is to allow many users to share a relatively few frequencies.
A trunking system is controlled by a computer. Information (data) is exchanged between the system radios and the computer on a control channel, sometimes called a data channel. It sounds like a strong buzz.
A large system can have up to 28 freqs., 4 of which may be used as control channels. The control channel may be changed once a day or as often as the programmer decides. Some scanners need only the control channels to track an entire system. Just put in the 4 Control Channels.

Each group of users (Fire, Police, etc.) is assigned TALK GROUPS. In a Motorola Type II system, the most common type, TGs are usually in 32 number steps starting with 16 and going up to 65536; 16, 48, 80 --- 4656, 4688, 4720 --- 28944, 28976, etc. System radios can have more than 100 TGs programmed into them.

After all the freqs. have been entered and it is "trunking", the Banks become SCAN LISTS where you enter the Talk Groups you want to hear.
Use the Talk Group numbers in the DEC column, not in the HEX column.

When a user pushes the talk button on his radio, data is sent to the computer. The computer chooses an unused freq. and sends that data to all the radios using the TG of the originating unit. This all happens in a fraction of a second and it happens EVERY TIME a radio is used.

EXAMPLE:
Fire Dispatch calling Engine 4 (TG 4528 on 856.7125)
Engine 4 answering Dispatch (TG 4528 on 852.2625)
Respond to 73 Elm Street (TG 4528 on 855.9625)
Engine 4 responding (TG 4528 on 851.6375)

If you have entered TG 4528 into your scanner, it will decode the control channel data and change your scanner freqs. to follow the conversation on TG 4528.

This should get you started, but you should read the manual carefully. You may need to read it several times.

EDACS and LTR systems use the same principles, but they can not do Control Channel Only trunking, the TG numbering is different and ALL the frequencies must be entered into specified channels in the scanner. EDACS channels are designated by a small number in front of each freq. in the database.
 

newsphotog

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If you have additional questions, check out the Iowa forum, lots of good info on RACOM there. Perhaps this thread would be better suited to be moved to the Iowa forum.
 
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