EMC166 Repeaters?
To:   Emergency Communications Units - Information Bulletin
To:   Emergency Management Agencies via Internet and Radio
By:   Auxiliary Communications Service (ACS) of the
      California Governor's Office of Emergency Services

EMC166  Repeaters?          For release 1/11/99

Sure, YOU know what a repeater is, and what it does.  But what
about the non-technically oriented staff in the emergency
management agency, such as the person with the money strings?
Or the manager who hasn't time to grasp the fundamentals of
communications?

Part of the task for the leaders of an all-volunteer emergency
communications resource - which we generically designate as an
EMCOMM UNIT - is to insure that such essential staff does
understand the function of repeaters and how critical they are
to emergency communications.

What, then, is a "repeater?"  A repeater is a specially built
radio with separate transmit and receive units.  It achieves its
major impact on an area when it is high on a building or a
mountain.  For that reason, tall buildings and mountaintop
locations are very important assets to a jurisdiction or agency.

A repeater will take in a signal on one frequency and send it
out on another, usually with a strong boost in signal strength.
Repeaters' sensitive receivers can pick up weak transmissions
(such as from a hand-held or vehicle-mounted transceiver) and
then rebroadcast them through a powerful transmitter.  In many
cases, repeaters include a connection to the telephone system
with an "auto-patch".  Users with the appropriate access codes
can then access the phone system.  While cellular telephones
offer a similar service, the wide and uncontrolled use of cell
phones causes overload to the cellular system.  Also, earthbound
cellular systems do not have continuous coverage in mountainous
areas.

Repeaters play a key role in disaster preparedness and response,
in that communications can be made in ways not otherwise
possible.  Strategic placement, as on a key mountaintop, allows
coverage of vast areas of terrain, often in ways not otherwise
possible.  For instance, repeaters atop Mt. Diablo in west
central California cover hundreds of miles of the center of the
huge state.

Yet, there ARE areas of the state that are blocked from
coverage, such as where other mountain ranges are barriers to
radio signals.  Hence, in Northern California with several such
ranges, signals from Mt. Diablo cannot be received in areas such
as Redding, Eureka, Yreka, Alturas, and others.  So, to
intercommunicate into/from and IN such areas, other repeaters
are needed.  In some areas it takes a multitude of repeaters to
create effective coverage and links.  The I-5 corridor of
northern California is one such example.  As I-5 winds its way
through the Cascade mountains past Mt. Shasta into Oregon, it
takes a certain placement of interlinked repeaters for effective
communications.

Repeaters are expensive equipment, with high technical standards
requiring quality components.  They operate 24 hours a day, 365
days a year, and do it for years.  Repeaters contain critical
circuits that allow them to transmit pre-prepared messages,
accept programming over the radio or a telephone, receive or
transmit in a tone-controlled manner, readjust time-limit
constraints, or accept coded access.  They are typically put in
environments extremely hostile to electronic equipment, like a
mountaintop snowbound in winter.  Maintenance of repeaters in
such locations can be a time-consuming and difficult challenge.
Because of the relatively high cost of repeater ownership and
operation, those used by Amateur Radio Service licensees may be
sponsored by local radio clubs or by unit membership dues if an
agency cannot provide, or assist with, the needed funds. end ---
Bulletins are on the ACS Web page:  http://acs.oes.ca.gov -and a
Landline BBS:  916-262-0856 (graphical & standard interface);
and a FTP Archive:  ftp.ucsd.edu/hamradio/packet/tcpip/incoming
for some bulletins.  For earlier ones:
ftp.ucsd.edu/hamradio/races