- Why is coordination necessary?
-
Frequency Coordination has
many purposes. These purposes
will vary from region to region, however the following reasons usually
apply in all areas.
To understand why frequency
coordination is necessary,
you must first understand the limitations of certain types of stations.
Changing frequency for most
modern home stations
is as easy as turning a dial or hitting a few buttons. The operator is
in close proximity to the transceiver and can easily compensate for
interference
from another station on a nearby frequency (or a distant station on the
same frequency) within seconds.
Virtually all repeater
stations will require one
or more frequency specific components such as duplexers, filters,
isolators,
circulators, multi-couplers, combiners, or other pieces of equipment.
In
addition, most repeaters use transmitters, receivers and in some cases
even antennas that cannot change operating frequency easily if at all.
Control receivers and link transmitters also must use fixed frequencies
for a variety of additional reasons. Control receivers must be on a
known
frequency in order to be accessible by control operators at a moments
notice.
Links must relay signals to other stations instantly. It is virtually
impossible
for a receiver to 'search the band' looking for the frequency the link
transmitter 'on the other end' happens to be operating on at any given
point in time. Similarly, it would be exceedingly difficult should an
operator
have to search the band for a repeater located in a specific area every
time (s)he wanted to call another operator. The repeater input and
output
frequencies must be known in advance. Not all systems can share the
same
frequency due to mutual interference, so each must operate on its own
unique
frequency or set of frequencies. The users of a particular
system
will then know where to 'find' it when needed.
Frequency Coordination is a
method to minimize interference
among these stations while maximizing use of the limited radio spectrum
available to the Amateur Radio Service by planning what specific
frequency
or frequencies a given station will operate on in a specific area.
Frequency
coordinators provide these planning services by maintaining records of
existing systems and by either approving or recommending frequencies
for
use by new stations.
This is a generalization of
what frequency coordination
is, but it should be quite sufficient for our purposes. Many areas have
different methods of employing frequency coordination, and it would be
very difficult to cover all of them. If you wish to know more about how
frequency coordination is handled in your area, please contact your
local Frequency Coordinator.
The frequencies used for
coordinated stations (commonly
called a 'bandplan' or 'frequency utilization plan' or something
similar)
vary somewhat in different parts of the country. To find out what the
'bandplan'
is in your area, please contact your
local Frequency
Coordinator. It is a good idea to know the bandplan in your
area even
if you do not use coordinated systems.
Frequency coordination is
also necessary, or at least
is in the best interests of all repeater stations, due to the following
FCC rule:
97.205(c).Where
the transmissions
of a repeater cause harmful interference
to another repeater, the two station licensees are
equally
and fully
responsible for resolving the interference unless the operation of
one station is recommended by a frequency
coordinator
and the
operation of the other station is not. In that case, the licensee of
the noncoordinated repeater has primary responsibility to resolve
the interference.
(Last
update 8-26-98)
Copyright
© 1998, NFCC, Inc.
All Rights Reserved.