Marshall Amplification Field Marshall 100 Owner's Manual page 29

Fences & Wires
A fence picks up your transmitter's signal, like an antenna, and the
signal races down the wire and re-radiates. Your receiver picks up
false signals which will most likely be horizontally polarized. The
effect is most pronounced when your target is right next to the
wire.
Checkerboard Patterns
When you are near the animal you may experience checkerboard
patterns (technically known as interference patterns.) If you plotted
the strength of the signal near your transmitter, it would look some-
thing like a round checkerboard. One spot is strong, while a few
feet away you get little signal.
Checkerboard patterns occur when the signal reaches your re-
ceiver over two different paths, one being line-of-sight and the
other a reflection off the ground. When the two signals combine
they complement each other in certain spots, nullifying each other
in others.
When the transmitter is close: The checkerboard effect is
most pronounced when your animal is off the ground in a
tree, especially when the transmitter antenna is pointing at
you. Checkerboard patterns can weaken the signal in the
direction of the animal while it remains strong in some other
false direction. It can throw you off by exactly ninety degrees!
Don't rely on signal strength alone to find the animal, espe-
cially up close, because you could have just moved into one
of the low signal pockets. Instead, rely on the directionality
provided by your antenna. Don't get too close. Circle where
you think the animal is. Use vertical polarization, since
ground doesn't reflect vertical waves well.
When the transmitter is distant: The checkerboard effect
simply makes the signal stronger in some spots. Therefore,
when you're trying to pick up a very weak signal, always
move around and try to get the signal at several spots within
a 15 foot radius.
Ow ner's Manual
Page 29