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    Default Trunked Frequencies?

    Hey All,
    What does it mean when a scanner frequency is refered to as "Trunked"?

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    I'm trying to work out your reply... hmmmm

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    Trunked radio systems are usually to be found in areas where digital has taken over from analogue systems. Basically, digital "frequencies" are agile and can move from area to area, without being affected by distance from their "home" radio masts. The signal given by the radio seeks out the nearest and best mast signal wise and attaches itself to that, enabling the frequency used to migrate from mast to mase as the user moves throughout an area. Scanner frequencies will trunk in the same way if they operate digitally.
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    But do the newer scanner models all have that capability? For exaple is my pro-83 a trunked scanner?

    (This is my post, just a differant name)

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    You can go to www.radioreference.com and get all the information you want on trunked systems and other radio stuff.

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    No, it is not. Look for an 800Mhz scanner. Also your area is probably not trunked if you've never heard of it before.

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    Trunking is a way to give many users space on limited frequencies. Say you've only got 6 frequencies available, but 15 different depts all with a dispatch and multiple fireground channels....a computer decides the best way to allocate the limited frequency resources and picks out the best freq to use out of the 6 and it won't always be the same each time you talk as it would be in a traditional vhf or uhf setup with a set tx and rx freq. Only problem is if everyone wants to talk at the same time (say at "the big one" or even a major severe weather outbreak), the system will get overloaded and your radio will honk at you when you try to key up. Those who are familar with operating on a trunked system are probably all to aware of the dreaded motorola honk!
    A trunk tracking scanner just decodes the computer talk on the system's control channel which allows it to know what freqs the conversation is going to be on the next time a user keys up.

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    Originally posted by martinm
    Trunked radio systems are usually to be found in areas where digital has taken over from analogue systems. Basically, digital "frequencies" are agile and can move from area to area, without being affected by distance from their "home" radio masts. The signal given by the radio seeks out the nearest and best mast signal wise and attaches itself to that, enabling the frequency used to migrate from mast to mase as the user moves throughout an area. Scanner frequencies will trunk in the same way if they operate digitally.
    You're describing like 3 different things, none of which are trunking. Digital is digital and doesn't neccessarily have anything to do with trunking. In fact, most systems whether trunked or conventional are NOT digital. Selecting multiple sites for receiveing is voting and again isn't trunking. Selecting among multiple transmitters can be a function of trunking with Automatic Multiple Site Selection, or a function of a conventional system with site steering.

    Trunking uses "virtual channels" called talkgroups. The enduser sees these talkgroups as channels in a conventional sense. You can have many many talkgroups (hundreds). The radio system might have say 5 repeaters for maybe 12 talkgroups. When a user on talkgroup 1 transmits, the radio tells the computer system "Hey, I want to transmit!" The computer sytem picks an unused repeater and tells all the radios on that talkgroup to go that repeater. This all happens in about 400 milliseconds and is completely invisble to the user. When you have the channel, your radio gives you the clear to talk tone (that little bee-beep) and your on the air.

    Advanced systems allow you to dynamicly regroup users and make all kinds of configurations on the fly. They can allow "private" radio-to-radio conversations without everyone in the talkgroup hearing it (Bring coffee!).

    Obviously, the whole thing relies on not everyone wanting to talk at the same time. You need to plan it to have the capacity for a major incident where "many" talkgroups may need to be active at once. If everyday radio traffic gives busy-bonks, it was not planned well or they cut corners to save money (typical).

    You can use several types of encryption if do desired. You an also use several types of digital modulation. The system can be layed out over a large area (region or statewide). Since it is all one big network, you can talk from one end of the state to the other. Anyone on the system would have interoperability with everyone else on the system.

    When it is built correctly, it is really a marvel of communications utopia. Unfortunately, corners are often cut for the sake of making a bid and getting re-elected. This makes the traditional crappy system that never works where you need it.

    To scan a trunking system, you will need a scanner with a feature set commonly known as "trunk-tracking". If you want to monitor anything that is P25 digital (trunking or not), you will need one of Uniden or RatShack's $500 digital scanners.
    Last edited by nmfire; 05-16-2005 at 11:51 AM.
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    Knew you could explain it nmfire. I know what it is just do not know how to explain or put into words. Thanks for posting so HeroOFTHEDAY can understand.
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    Thanks so much guys, I think I understand it now to a degree. Again this is HOTD, I just changed my name.
    So basically I shouldn't be concerned about trunked frequencies at this time?

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    Originally posted by Pierce151
    Thanks so much guys, I think I understand it now to a degree. Again this is HOTD, I just changed my name.
    So basically I shouldn't be concerned about trunked frequencies at this time?
    Depends on what system the people you want to listen to have.
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    Really, the only important frequency is my dispatch frequency, which happens to be the police department. I like to also listen in to other local dispatches on my scanner (As oppossed to just my pager), and in my travels to find local frequencies I came upon the term "trunked", so I was eager to understand that term.

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    Unless one of the agencies you really want to listen to is using a trunking system, no you don't need to worry about it.
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