From: lockhart@mothra.nts.uci.edu (Jack C. Lockhart)
Subject: A reply about 800 MHz Trunked Radio Systems
Summary: Inquiry about Trunked Radio Systems
Newsgroups: rec.radio.amateur.misc,rec.radio.amateur.policy
Organization: University of California, Irvine
Keywords: 800 MHz, Trunked Radio Systems
Date: 15 Jun 92 22:30:41 GMT
Followup-To: rac.radio.amateur.misc,rec.radio.amateur.policy


A couple of weeks ago, someone from Illinois posted a request for
information on 800 MHz Trunked radio systems.  I accidently deleted
the message before I could answer.  If you are that person, please
send e-mail.  I have some information on trunked radio systems that
may be of interest to you.

~jack_



WHAT IS TRUNKED RADIO  FROM J. LOCKHART


A.   WHAT IS TRUNKED RADIO?     June 14, 1990

    A trunk radio system can be viewed like a "telephone switchboard
in the sky".  The trunking concept disassociates the user from a
dedicated radio channel.  Trunking is a computer controlled system
whereby groups of users with a common interest can share a radio
system.  They are on solitary and dedicated talk channels.  In fact, a
trunk radio system is much like the land based telephone system.  Land
based telephone or its cellular radio extension consists of a
dedicated person-to-person conversation sharing facilities with
others.  In trunking, groups of users talk together much like the old
party line telephone system.  Trunking systems have many specialized
options such as paging and telephone interconnect that adds
flexibility to the System.  The point is that the radio channels are
not dedicated to the users group.  The users are in groups or systems
and their radio channel use is transparent to the users.  In this way,
traffic sharing improves radio spectrum utilization.  The benefit is
both the intermittent use of channels and the time of day demand
shifts of user groups.  For example, on a local Government system
during normal working hour Utility, Public Works, and Administration
typically may have higher volume communication needs lower than
Police, Fire, and Rescue users who may have relatively lower
communication needs.  During the evening and night time hour of high
Public Safety incidents, the operating groups of Utilities, Public
Works, and Administration are normally shut down with little or no
demand for communications.

    Because of its computer controlled nature, a specific compensated
feature exists.  For example, a group may be altered and integrated
into larger groups comprised of groups from different agencies.  The
trunking system could consist of only public safety, a whole City-Wide
system, a Utility system, or a shared ownership system between
governmental entities.  This is referred to as partitioning a system.


C.   WHAT MAKES TRUNKING DIFFERENT?

     Trunked radio systems are different From conventional radio
systems in several key respects.

     o The first characteristic is a large up-front cost.
       Although recently there have been some modifications
       regarding a lower entry level, there remains a higher up-
       front fixed cost than most conventional systems.

     o Unit add ons (mobile, personal, and control station
       radios) are locked into the land based vendor or its
       licensed agents.  Therefore, you cannot do extensive
       comparative shopping after making a commitment on the land
       based system supplier.

     o No one particular user group directly owns or has claims
       on the radio frequency or hardware; it is shared by the
       groups.  This means the groups have a common ownership
       (system controller).

     o The add-on units can be more expensive than typical low
       band, high-band or 450 MHz units because of their locked-
       in nature and their more sophisticated computer controlled
       capability.  However, low end trunk units can be purchased
       for approximately the cost of high end convertional system
       units.

                          POSTS FROM USENET

>From usc!cs.utexas.edu!swrinde!mips!zaphod.mps.ohio-state.edu!hobbes.physics.uiowa.edu!moe.ksu.ksu.edu!matt.ksu.ksu.edu!news Wed Sep 11 15:37:37 PDT 1991
Article: 7070 of rec.radio.amateur.misc