13-6. Lowering Procedure
Lower the antenna as follows:
vertical structure. Making a small coil of the rope
a. Untie the ropes and lower the antenna to the
will facilitate throwing it over the vertical structure.
b. Disconnect the coaxial cable from the antenna
The antenna reel housing may also be
secured to a single vertical support
e. Loosen the wire lock knobs and free the wires.
structure, and the elements tied off at
ground level with the guy ropes (fig. 13-
Keep fingers clear of the wire as it is
Under certain environmental
wound on to the reels.
conditions, such as high wind and/or heavy
d. Wind the wires onto the reels.
ice loading, this method is more desirable.
e. Coil and tie the ropes.
Section III. OPERATION
indicated by a dial that is calibrated in frequency.
Figure 13-3 shows frequency versus per side wire
length. The wires are secured at the desired length
The Collins 637T-2 consists of two reels of
with the wire lock knobs mounted in the housing.
phosphor-bronze wire stored in a cylindrical
The end of each wire is attached through a swivel to
housing. Prior to unreeling the wires, set both wire
a length of nylon rope. The antenna is then raised to
length indicator pointers to zero.
the desired height by passing each rope over a tree
limb, tower, or other vertical structure. Connection
13-8. Operating Frequency Selection
to the equipment is made with standard 50-ohm
For operation at a particular frequency, each wire is
coaxial cable (before raising).
pulled out of the housing to the correct length as
Section IV. OPERATING PRINCIPLES
balanced dipole circuit by a ferrite balun contained
in the antenna housing. Figure 13-4 shows the balun
and antenna connections.
The Collins 637T-2 operates as a conventional half-
wave dipole (fig. 13-4).
characteristics of a dipole antenna are dependent on
The Collins 637T-2 provides good gain on path
its height above ground.
Figure 13-5 shows
lengths varying from 0 to approximately 1,000
calculated elevation plane patterns at an average
miles. Longer paths require multiple hops. Figure
height of 25 feet.
13-5 shows the field intensity radiation patterns to
be expected for the various frequencies.
unbalanced transmission line is matched into the
Section V. MAINTENANCE
To disassemble the antenna, refer to the exploded
view in figure F O 2 and proceed as follows:
a. Remove the retaining ring (9) from the rod
The Collins 637T-2 requires a minimum of
assembly (12) at either end of the antenna.
maintenance. Periodically, the antenna should be
b. Remove the three flat washers (10).
disassembled, and all gears washed with soap and
c. Unscrew and remove the clamp indicator
d. Remove the dial indicator assembly (13, 14).
13-13. Disassembly Procedure
e. Remove the dial assembly (21, 22).