Vectronics VEC-896 - Manual (Page 11)

VEC-896 Vertical Antenna Instruction Manual
10
24. Use the three wire ties to affix the coax to the antenna as illustrated on the inside cover.
Warning: To prevent arcing and destruction of the coax cable, do not allow the coax to
come within 1 inch of the base mounting bracket.
25. Slide a hose clamp over the top element. Mount the top coil assembly to the antenna by
inserting the fiberglass insulator in the top element. Tighten the bus wire from the coil
assembly under the hose clamp. Make sure the loading coil assembly is secured.
26. Mount the coil assembly with the angle mounting bracket three to four inches from the
bottom insulator of the antenna. See figure on inside front cover.
27. Double check the tightness of all the hardware you installed and then mount the antenna
on the short temporary tuning mast (6 to 8 feet).
28. Tune the antenna, see the next section.
29. Mount the antenna in its permanent location. Slight re-tuning may be necessary.
FREQUENCY AND SWR ADJUSTMENT
This antenna covers wider frequency ranges on the higher bands, and narrower segments on the
lower frequency bands. The 40 meter band has the narrowest range of operation (approximately
40 KHz) and is the most sensitive to adjustments.
The entire antenna must be accessible during initial coarse tuning and testing. Any repair or
adjustment to the antenna after it is installed on a tall support will make adjustments difficult and
time consuming. It is best to install the antenna on a short temporary mast or pipe that is located
in a reasonably clear location for tuning. The antenna should be mounted vertically with the base
of the antenna around six feet above ground to make tests and adjustments easy.
Hint: The use of a small tripod will make tuning this antenna easy. With the help of another
person it is easy to lean the antenna, while it is fastened to the tripod, to lower it and
make the necessary adjustments.
The SWR can be measured by using a transmitter and SWR bridge or an SWR Analyzer such as
the Vectronics SWR-584. The best location to make SWR measurements is at the base of the
antenna. If the measurements are not taken at the base of the antenna, the antenna must be fed
with a reasonably short length of good quality 50 ohm coaxial cable to insure proper results. If
using a transceiver and SWR meter, set the transceiver to the lowest power possible to make
measurements.