MFJ
Super Hi-Q Loop
™ Antenna Instruction Manual
4
The broadside horizontal radiation that occurs in a small vertical loop is mostly above 10 degree wave
angles and extends straight above the loop and to the opposite 10 degree elevation point.
True
vertical polarization occurs only in line with the loop
. As you move around the loop towards the
sides, the pattern "skews" and eventually becomes completely horizontal broadside to the loop.
Unlike linear verticals,
vertically polarized small loops
also radiate straight up and
down from the antenna. This
high angle radiation can be used
to cover short distances by sky
wave. The high angle horizontal
radiation in a vertically
polarized loop antenna occurs
because the ground below the
loop is either too far away or is
not a good enough RF reflector
to cancel the horizontal
radiation component of the
vertical loop.
This effect can be reduced by laying a screen or grid of wires that extend for at least 20 feet each
direction from the antenna just below a vertically mounted loop antenna, or mounting the loop
vertically over a large metal roof.
HORIZONTAL POLARIZATION
Horizontal mounting of the loop antenna results in an omni-direction, horizontally polarized pattern
that has a null straight up in the air and straight below the center of the antenna. This means that any
ground reflection will tend to cancel the radiation along the horizon, and also at low wave angles
unless the loop is mounted some distance above ground. Mounting a horizontal SMALL loop antenna
just above a good reflecting ground will practically guarantee no useful signal in any direction!
Note:
Do not expect the best results if you mount this loop antenna horizontally if it is less than 20
feet above a metal roof or other ground plane!
Since ground wave signals only propagate well along the earth when they are vertically polarized, a
horizontally polarized loop may not respond to some local noise sources. Like all other antennas, a
small loop is generally a quieter receiving antenna when horizontally polarized. This also means that a
horizontally polarized loop is not a good choice for local ground wave communications. However, it is
an excellent choice for medium to long distance sky wave communications.
Figure 4
