Conventional and Trunked Radio QUESTION

[SCPD]

OK, so I know there are two types or radio systems... trunked and conventional. so my question is i know that with trunked the towers tell the radio what frequnecy to go to to transmit on and they are all linked together well with conventional how does it work? if there are 30 different channels does there need to be 30 seperate repeaters also? or can one repeater serve for all the 30 diff channels? as how they can with trunked radio systems.

 

[greenthumb]

Here is a link that should take care of most of your questions:

Trunked Radio Systems - The RadioReference Wiki

Enjoy!

 

[fineshot1]

OK, so I know there are two types or radio systems... trunked and conventional. so my question is i know that with trunked the towers tell the radio what frequnecy to go to to transmit on and they are all linked together well with conventional how does it work? if there are 30 different channels does there need to be 30 seperate repeaters also? or can one repeater serve for all the 30 diff channels? as how they can with trunked radio systems.

Not all conventional channels are going to have a repeater. This would depend on
how each conventional channel is configured, you would have to ask the agency
who it belongs to or try and figure it out from the fcc license info.

 

[SCPD]

Not all conventional channels are going to have a repeater. This would depend on
how each conventional channel is configured, you would have to ask the agency
who it belongs to or try and figure it out from the fcc license info.

thanks ok so if there are 30 different REPEATER channels do they all need seperate repeaters for all 30 channels? thanks.

 

[fineshot1]

thanks ok so if there are 30 different REPEATER channels do they all need seperate repeaters for all 30 channels? thanks.

A repeater operates on a pair of frequencies.

One freq for RX and one freq for TX at the same time.

If you have 30 freq pairs then you can have 30 repeaters.

You can not have a repeater do multiple freq pairs(in most cases)
unless it is a special configuration.

I hope that clears it up for you cause i don't know how to explain it any simpler.

 

[WA0CBW]

As fineshot1 said each pair of frequencies requires a repeater. This is because the duplexer for each repeater is tuned to a single frequency. Same goes for trunked systems, for every frequency pair there is a repeater. However in a trunk system the controller determines which repeater (frequency) each talk group will use. This information is sent out by the controller on the control channel and tells your radio to switch frequency to that repeater for the talk group your are on. A talk group is a group of users who have their radio channel selector turned to the same talk group. This is why a conversation can be on a different frequency for each push to talk. The controller tells the radios (and your scanner) what frequency to go to and after the conversation goes back to the control channel to listen for what frequency all the talk groups are directed to. The switching from frequency to frequency takes place in a little over a quarter of a second.

Hope that helps.

BB

 

[SCPD]

great thaanks guys! that helped a lot... it seems like trunked system is a better way to go as far as a radio system is concerned but it seems way more complicated.

 

[RKG]

great thaanks guys! that helped a lot... it seems like trunked system is a better way to go as far as a radio system is concerned but it seems way more complicated.

I wouldn't make that assumption; it depends entirely on the nature of the operator's function, the number of units he has in the field, and how they are configured in terms of what they do.

The basic difference is easier to understand if you accept that "channel" can have two different meanings. Logically, a channel is a group of users who have to talk to one another and (in most cases) whom you want to be able to hear what everyone else is saying.

Physically, a channel is a radio path by which the members of the logical group communicate physically.

Before trunked radio came along, the two concepts were linked: for each logical channel you wanted or needed to perform your function, you needed that number of physical channels.

Trunking was designed to solve two problems. First, there simply weren't enough frequencies to give everyone as many physical channels as they wanted. For instance, before trunking, the Massachusetts State Police had a total of 7 physical/logical channels for the whole state. Today, they have over 100 logical channels but only 28 distinct physical channel pairs. Second, the fact of the matter is that, even in public safety, a dedicated physical channel spends most of its time idle. If you pull statistics from a voter, you'll find that your typical Fire Department's main dispatch channel is actually transmitting less than 1% of the time during a 24-hour period, and a typical Police Department's main dispatch channel seldom transmits more than 2-3% of the time. The rest of the time, the channel is idle and not in use, but you can't use its idle time for anything else, because when you need it for your Fire or Police function, you need it right now.

What trunking does is to separate logical channels from physical channels. In its simplest form, an agency might have five repeaters set up. One is dedicated to data; the other four are available for voice. When a member of a logical channel group keys up, the system picks one of the idle voice channels and assigns it for the use of that logical group. A data command causes each radio selected on the logical group to switch to the voice channel for the required communication; when the communication is completed, the radios switch back to the data channel and wait for another command.

Now things get complicated when you decide to set up voted satellite receivers or if you decide to set up a simulcast system, but the basic principles are as set forth above.