Vectronics VEC-1856 - Manual (Page 8)

VEC-1856 Instruction Manual 6 Meter Ground Plane Antenna
8
TUNING THE ANTENNA
After the antenna base with radials has been secured to the mast, refer to Chart 1 to tune
the antenna to the desired frequency. Locate the radiator. This is the 54 3/4" hollow tube
that is threaded on the inside at one end. The radiator length is factory set for 50 Mhz.
To tune the antenna to other frequencies, cut the radiator with a hacksaw or tubing cutter.
Do not cut the radiator at the threaded end! Once the radiator has been cut the change is
permanent!
Chart 1 Cutting measurements for tuning between 50 and 54 Mhz.
FREQUENCY RADIATOR LENGTH CUT LENGTH
50 Mhz 54 3/4 INCHES 0 INCHES
51 Mhz 52 7/8 INCHES 1 7/8 INCHES
52 Mhz 51 INCHES 3 3/4 INCHES
53 Mhz 49 1/8 INCHES 5 5/8 INCHES
54 Mhz 47 1/4 INCHES 7 1/2 INCHES
After cutting the radiator for the desired frequency, place the 1/4" endcap over the end
that is not threaded. This will prevent the antenna radiator from becoming filled with rain
water. Attach the radiator to the antenna base by hand threading the radiator over the 10-
32 screw on the top of the base as shown in Figure 9.
Figure 9 Antenna with radiator attached.
After cutting the radiator to the correct length, adjust for lowest SWR by squeezing or
spreading the center of the matching stub.