WJFM: Nation's Most Powerful FM Station!
93.7 on the FM dial has become a household term to more than 150,- 000 families in Western Michigan. For 21 hours each day, WJFM radiates its powerful voice of 11, million watts (ERP) over some 30 counties and dozens of communities. WJFM began broadcasting with this tremendous power (the next highest FM station power is about 260 kw) on November 15, 1961, a significant date for FM listeners in about a third of the state because it meant they could receive noise-free radio programs whether their receivers were small, large, cheap or expensive.
It brought on a resurgence in the purchase of FM receivers within the area, especially in localities which had never before received FM. November 15, however, represented not the beginning, but, rather, the climax of a continuing effort to provide FM to the vast listening public of Western Michigan.
The Beginnings of WJFM
The birth of WJFM goes back
to 1946, the year Fetzer Broadcasting obtained its first construction permit for the facility. This
CP was for the unheard-of (in those days) power of 500,000
watts. The company was confronted with many complications:
Equipment capable of producing
500,000 watts was not readily obtainable; also, there was the problem of a suitable antenna site with
adequate ac power available for
such a powerful transmitting plant. (Over 150 kilowatts, 21
hours a day, are needed to provide
the 50-kw transmitter output used
today.).
In 1950, Fetzer constructed
WKZO-TV, and it was determined
that the TV tower would also be
suitable for an FM antenna transmitting at reduced power. Thus, on
June 25, 1951, WJFM took to the airwaves with an effective radiated power of 115 kilowatts. For
the next 10 years WJFM's income
was not large enough to pay the
power bill, but Fetzer had great
faith in the future potential of
FM and felt it was in the interest
of the radio public to keep the facility on the air.
To realize some income from the
operation, a Muzak franchise was
purchased, and the first multiplexed operation in Southwestern
Michigan went on the air .The anticipated increase in power would
eventually produce even greater
multiplex potentials, a factor supporting the initial decision to purchase the Muzak franchise. All
this, remember, took place during
the years when many FM stations
were going off the air.
WKZO Moves to Gun Lake
KZO Moves to Gun Lake
During 1960, Fetzer management decided it was time for a
modernization program. Their conclusion: to locate the WKZO-TV
transmitter and antenna at a point
midway between Kalamazoo and
Grand Rapids, to serve both communities. Management further
reasoned that the new antenna
tower would be an excellent location for WJFM's antenna.
To keep WKZO-TV's signal on
the air during the move from
Kalamazoo to Gun Lake, management purchased a new TV transmitter. The two 25-kilowatt TVpower amplifiers at Kalamazoo
were designated for the FM operation. These were Type TT25AL amplifiers, and it was a relatively simple task to raise their
operating frequency to 93.7 mc,
diplex the amplifiers, and raise the 10-kw output of the new RCA
Type GTF-10D driver transmitter
to 50 kilowatts.
Amplifier Conversion
The power amplifiers use the
well-known cluster of seven 5762
triodes operating in a parallel,
grounded-grid configuration. This
cluster design, owing to the physics of VHF frequencies and the
mechanics involved, lends itself excellently to frequency conversions. The modifications resulted
in the first BTF-50B transmitter,
and system performance has
proved very satisfactory.
Side-Mounted Antenna System
WJFM uses a 12-section,
gapped-ring antenna to one leg
of the TV tower at the 800-foot
level. Center-fed, this array provides a power gain of 12.5 and
raises the 50-kw transmitter out put to 500-kw ERP. Mounted on
one leg of the triangular crosssection tower, the antenna provides substantially circular coverage over a 25,000 square-mile area
(90-mile radius). This area includes Kalamazoo, Battle Creek,
Grand Rapids, and Lansing, plus
dozens of smaller municipalities
at all points of the compass. In
addition, the signal covers a large
rural area that would not otherwise receive FM service.
Building Features
Both the TV and FM transmitters are housed in a modern, wellengineered building of prestressed concrete. The 1100-ft antenna tower stands immediately outside to minimize outdoor horizontal runs of transmission lines. Locating the tower so close to the building presents a falling ice problem during Michigan winters; this was overcome through a speciallydesigned roof that withstands potential damage.
All the electronic gear associated with the transmitters is located on the basement level with
the power transformers and blower equipment. This setup keeps the
transmitter room on the floor
above extremely quiet. Further,
this arrangement considerably reduces blower vibration in addition
to increasing accessibility to the
equipment. All of the air is filtered prior to its entry, eliminating the need for individual air filters for the blowers. Outdoor air
is first filtered through spun-glass filters, then passed through electrostatic filters to axial fans which
"pressurize" the basement room
and thus make it a massive plenum chamber.
The blowers, mounted on concrete piers, push the filtered air
upward through the basement ceiling and into the bases of the
transmitter equipment. Ducting,
at the top of the transmitter cabines, is thermostatically controlled
so that the warmed air from the
equipment goes directly outdoors
in summer, or indoors in winter to
heat the transmitter room. This
loop system, using outdoor air, reduces the BTU requirement of the
air-conditioning equipment in summer and delivers fresh, warm air
in winter.
In addition to providing a dustless atmosphere in the transmitter
room, another advantage in prefiltering the air is the elimination
of a settled-dust problem in the
basement. This, of course, simplifies maintenance.
WJFM Programming
When the station went to the
half-megawatt power, management decided it should be an
entity in itself and should therefore generate its own programming. The staff spent many
months making audience surveys
to devise the programming that is
now a part of everyday operation.
As a result, WJFM programs its
educational and informational
shows throughout the day instead
of just during the early hours of
the morning. The surveys also indicated that listeners desired large
blocks of time set aside for each
musical category. As a result,
WJFM maintains a considerable
disc and tape library which provides an excellent range of musical selestions.
FM Stereo Programming
From 8:00 A.M. to Midnight
each day, WJFM transmits multiplex stereo, using a stereo subcarrier generator mounted in the
center cabinet of the FM transmitter. Since introducing stereo
programming, WJFM has built up separate stereo-record library
of nearly 2,000 albums.
Commercial stereo tapes are run
through a four-track playback
head. The recorder is also equipped
with separate erase, record and
play heads for two-track stereo
tapes. The machine plays virtually all quarter-inch tape recordings
—full track, half-track, half-track
stereo and four-track stereo tapes.
The dual-channel consolette is
in the center of a horseshoe arrangement, with turntables on
both sides of the announcer's station. Each turntable contains two
preamps for stereo reproduction.
Cueing is incorporated within the
consolette. An RT-37A cartridgetape machine serves ideally for spot announcements, permitting
greater use of the turntables for
program material. The cartridgetape facility serves for both stereo
or monophonic announcements.