Marshall Amplification Field Marshall 100 Owner's Manual page 36

Field Marshall Tracking Receiver
The ultimate way to get up high is to hire an airplane and circle
the area, using a yagi antenna mounted on the wing struts,
pointing at an angle downward. Be sure to use good head-
phones in a plane. You'll need a long piece of antenna coax
with the right connectors on each end.
Getting Hot
When you're close to the transmitter, it's tempting to rush in to
find the bird or dog. However, you will do well to keep taking
frequent bearings to avoid overshooting its location. You may
have come to this spot based on a reflection while the main
signal was obscured by an obstacle. Once you're past the
obstacle the real signal may actually be behind you. So
continue to take 360° readings as you proceed close r.
Before setting out on foot, make sure you're within walking
distance. You'll waste a lot of time if you leave your vehicle
prematurely. Triangulation will give you a good clue how close
you are, or you can use the Meter technique described above.
Reduce your receiver volume and switch to Medium or Near
range as you get close. Don't remove your antenna as you may
do with other receivers. The Field Marshall Receiver has
exceptional shielding that maintains sharp directionality even
when you walk to without a few feet of the transmitter.
Continue triangulating, circling around the apparent location at
a distance and taking multiple bearings. Then just walk to
where they all intersect. Look out for reflections from fences
and other metal objects, which will be much stronger when
you're close to the transmitter. If the transmitter antenna
happens to be pointing at you you'll get the weakest signal
while the strong broadside radiation may reflect off nearby
objects giving much stronger signals in those directions.
Page 36