Vectronics VEC-1862 - Manual (Page 7)

VEC-1862 Instruction Manual Six-meter Yagi Antenna
7
with only a minor loss in gain with both antennas mounted at the extreme ends of the
pipe.
In order to feed two antennas with 50
Ω
line, you'll need to make a simple phasing and
matching harness. The harness is made from readily-available 75
Ω
line. Either solid or
foam-dielectric RG59 is suitable for this purpose. Prepare your harness as follows:
[ ] Cut one (1) electrical-wavelength of RG59. Be sure to use the correct velocity factor
for your particular cable (155-5/16" for 0.66 VF solid dielectric and 186" for 0.79 VF
foam cable). If your cable has a different VF (velocity Factor), use the formula:
Length in Inches = 11800 x VF / Freq. in MHz
[ ] Install three (3) FB43-5621 ferrite sleeves at each end of the cable.
[ ] Prepare pigtails with lugs at each end (see previous instructions for RG8M).
[ ] Cut the RG59 1/4-way down its total length and install PL-259's (at 38'3/4" for 0.66
VF solid or at 46-1/2" for 0.79 VF foam).
[ ] Splice the RG59 back together using a coaxial type "T" adapter--this becomes the
antenna array's 50-Ohm feedpoint.
[ ] Connect pigtail ends to the antennas. Note that this "off-center fed" harness shifts
signals 180-degrees out of phase. To correct for this, be sure to transpose pigtail
connections at the second antenna. If you don't do this, the yagis will be fed
out-of-phase and signals will cancel rather than add! You must install the
harness as shown below:
50-Ohm Feed
RG59
RG8X
Top Antenna
Bottom Antenna
Harness
PORTABLE OPERATION WITH THE VEC-1862
Although designed for permanent roof-top installations, your VEC-1862 makes an ideal
portable antenna. Its unique construction permits you to remove the elements in less than
a minute for easy storage or travel. To prepare for transport, simply remove the six #10-
32 element mounting screws and detach each element sections from the boom. The