History of the Bainbridge Gap Filler Site:
During the late 1950's and early 1960's, in support of an US Air Force Defense System, a large number of gap-filler radar sites were deployed across the United States. Having a range of around 65 miles, these radar sites were placed in areas where it was thought enemy aircraft could fly low to avoid detection by the longer-range radar of the permanent and mobile radar networks. These unmanned gap-filler sites generally were located at a prominent point and typically occupied an acre of land. An L-shaped building housed the radar and data transmission equipment in one section and one or more diesel generators and electrical equipment in the other section. A three-legged tower supporting a rotating dish reflector antenna was located at the end of the radio section. Maintenance personnel made periodic visits to the site, otherwise these sites ran on remote control.
Brookfield, Lewisville, Marblehead, and Bainbridge were places in Ohio which hosted these radar systems. The Bainbridge site, hailed as the 2nd highest point in Ohio, was known as the Bainbridge Gap Filler, SAGE # Z-43A or P-43A. The site was built in 1961 and in operation by April 1963.
At this site, the radar system was an AN/FPS-18 (Army-Navy Fixed Radar Detection & Range Direction Finding) short range search radar, built by Bendix. There were identical dual transmitters and receivers which operated automatically. If one channel failed, the other channel was automatically interchanged with the defective one. A liquid cooled V-87B Klystron operating around 1.2 kilowatts powered each transmitter. The radar system sent one microsecond pulses at a rate of 1200 pulses per second in the S-band at a frequency between 2700 and 2900 MHz to detect aircraft.
Waveguide, and a waveguide switch (for failure switching) linked the radio systems to the antenna tower. The towers ranged in height from 27-85 feet tall. The search pattern was limited vertically from .5 to 30 degrees above horizontal, with a horizontal beam width of 1.4 degrees. The parabolic antenna rotated at a speed of 5.33 revolutions per minute (one revolution in 11.25 seconds), and weighed over 2900 pounds. Depending on local climate conditions, the antenna was sometimes enclosed in a large dome.
Received radar signals were displayed on a small local display unit, though it was rarely viewed locally by personnel, except during maintenance. Using a barrier grid storage tube, video images were slowed to allow transmission over telephone lines to the primary control area at Wright-Patterson AFB.
The Bainbridge site operated on 120/208 volts AC, via a 3-phase, 4-wire, 200 amp commercial power service. In event of power failure, two 60KW diesel generators provided backup power (primary and redundant). These generators weighed in at 2000 lbs each and were fed by 1500 gallon storage tanks. It is reported that although the units were supposed to automatically start and switch over in event of commercial power failure, they rarely operated as designed on many sites.
By the late 1960s, new detection systems came online and the FPS-18 sites became outdated. The Bainbridge site was soon closed in December 1967. The site was stripped of all equipment and was declared excess to GSA in 1969. It was sold to private ownership in 1970, and was reportedly used for storage.
A local amateur radio operator acquired the site during the 1980s. A tower was constructed and space began being rented to various organizations. In November 1989, SVARC obtained the 146.925 Hamtronics repeater and it was installed at the site. In 1992, a 300 foot commercial tower was erected on site. In October 2001, Southern Ohio Communications Services purchased the site and is the current owner.
Today very little remains to tell of the sites former life. A few filled-in holes show where waveguide, exhaust pipes, and conduit passed through the walls. Less-worn paint spots and anchor bolt holes show where the generators, control panels, and transfer switches were installed. Tiles on the floor in the radio room are slowly detaching, an empty telephone terminal box stands silent along one wall. One of the original radar tower foundations now serves duty as base to the 925 antenna tower.
In addition to the W8BAP 146.925 repeater, there are several other occupants on the site. Among these are the KD8FJH 443.625 repeater (linked to the Central and Southeast Ohio UHF network), Paint Valley school bus repeater, a paging system, Ross County Sheriff repeater remote, and several ambulance service repeaters.
Nearby this site stood the Farrell Hill Fire Tower, made by Aeromotor, and erected in 1938. It rose to 80 feet above ground. It was dismantled in August 1978 by Dean Forest Service. A MARCS (Multi-Agency Radio Communications System) tower site now sits approximately where this fire tower once stood.
Thanks to the folks at the Radomes website: (
visit link) for much of the information, as well as some local people who've helped "fill in blanks".
December 2008 by Crystal Sound - this writeup originally appeared in the Scioto Valley A.R.C. December 2008 newsletter.
Note: Additional photos to be added soon. I've missplaced them. See "nearby waymarks" for additional photos and information, as this site has been waymarked under several categories.