There are thousands of ham radio repeater installations on the air across the U.S. in just about every location you can imagine. Some are installed in backyards on short towers, others are located on tall buildings, on water tank towers, shared with area police and fire department towers, and many are installed at commercial broadcast radio and TV station locations using very very high towers. Others are even on top of high mountains that serve a very wide area.
In very populated states and cities like California, Florida, New York and other major highly populated locations, just putting repeaters on the air on just any random frequency without frequency coordination within a ham band, would cause immense interference between them.If every ham radio repeater was not frequency "coordinated" then many would be unusable, especially in times of emergency due to many being on the same frequencies.
As you should know, the repeater antenna is the most important part of any ham radio station so it should be installed as high as possible for better coverage over a wider area. This increases the repeater range usually but if the respective repeater that is using that antenna is on a transmit frequency that happens to be on or near the input frequency of another nearby repeater, then interference to the other repeater may result.
So to help remedy this, frequency coordination for ham radio repeaters is a must in most locations in the U.S. Even yours!
There is an established group of ham radio operators across the U.S. that keep extensive records of repeaters, repeater input, output and control frequencies, including those not published in directories, or on the internet repeater data bases. This group of repeater frequency coordinators are volunteers and are "charged" with and recommend frequencies for a proposed repeater in order to minimize interference with other repeaters and simplex operations across your state.
Therefore, anyone considering the installation of a ham radio repeater should check with the local frequency coordinator for their area prior to such installation.
They will need lots of information from you as the repeater control operator in order to "OK" your proposed frequency/s, antenna height, erp and lots more. Be prepared to have several proposed frequencies in case they do not OK your first choice. Don't be dissapointed if you don't get your desired repeater frequency in highly congested repeater areas.
§ 97.3 Definitions.
(a) The definitions of terms …
(22) Frequency coordinator. An entity, recognized in a local or regional area by amateur operators whose stations are eligible to be auxiliary or repeater stations, that recommends transmit/receive channels and associated operating and technical parameters for such stations in order to avoid or minimize potential interference.
(c) Where an auxiliary station causes harmful interference to another auxil-
iary station, the licensees are equally and fully responsible for resolving theinterference unless one station’s operation is recommended by a frequency coordinator and the other station’s is not. In that case, the licensee of the non-coordinated auxiliary station has primary responsibility to resolve the interference.
§ 97.205 Repeater station.
(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 non-coordinated repeater has primary responsibility to resolve the interference.