Marshall Amplification Field 4000, Owner'S Manual

Page: 25 / 40

Page 25
Ow ner’s Manual
Hint:
Absence of polarization can be a clue. Suppose you’re
in a canyon and get a strong reading from a canyon wall. Either
your transmitter’s up there, or it’s a reflection off the canyon
wall from somewhere else. Before climbing, check the polarity
of the signal. If it’s a reflection the strength won’t change much
as you rotate the yagi around its axis.
Yagi Pattern
The Stealth Antenna is a form of directional antenna called a
yagi. It receives signals better in one direction than in others,
and that’s the only way you’ll find your animal when it’s out of
sight. Listening to the strength of the signal alone is almost use-
less, unless you have a lot of time to travel. You need a bear-
ing. The yagi also has gain, picking up weak signals better as if
it were amplifying them. It can pick up a far away transmitter
when other antennas would get nothing.
A yagi can best be described by its radiation pattern. It always
has a distinct forward lobe in the favored direction. The width of
the forward lobe is its beamwidth, the range over which the
antenna picks up strong signals as you scan across the
horizon. A sharper beamwidth allows you to pinpoint the
direction to your animal more precisely, like a spotlight
compared to a floodlight.
Yagis also pick up signals in other directions besides forward.
The back and side lobes can confuse your ability to determine
the direction to your animal. The strength of the forward lobe
relative to the back is known as the front-to-back ratio, a higher
ratio being better.