Radio Propagation - Marshall Amplification Field Marshall 100 Owner's Manual

Field Marshall Tracking Receiver
Radio Wave Propagation
Radio waves normally travel in straight lines, but like light, they
can also play tricks. Unless you do your hunting on an utterly flat,
dry, treeless plain, you will experience all of the deceptions below:
Reflections
Radio waves reflect under many conditions and the result is
always an illusion. You think the transmitter is behind the point of
reflection, but it isn't so.
Suppose, for example, you pick up the signal coming from the side
of a mountain. You spend hours climbing to the place only to find
no transmitter there. It never was there. What you saw was the
reflection of the transmitter's signal from another valley. You're
comforted by the fact that without a reflection you would have
no signal at all.
Radio waves reflect off any surfaces that conduct electricity, in-
cluding the following:
• Metal is the ideal reflector. Reflections from your nearby
vehicle can easily give you a false reading and the steel in a
building can scatter the signal in every direction.
• Water is another good conductor. Radio waves will bounce
off the surface of a lake like light off a reflecting pool.
• Hills and mountains reflect, but their properties will depend
on the nature of the material in them, particularly the mois-
ture they hold; wetter structures reflect better. Most natural
structures will give significant reflections.
• Liv e trees reflect radio waves, but dry wood does not. A
forest can scatter the signal in many directions. Any green
plant more than a meter in size can do it.
Radio reflections occur just like with a mirror, in that the angle the
wave comes out is the same as the angle going in. A flat surface
will reflect the signal in only one direction (the concept behind the
flat, angular surfaces of Stealth aircraft), while a rounded surface
will reflect in many directions, and most natural surfaces behave
like that. Multiple reflections are possible and a signal may funnel
a long distance down a canyon through successive reflections.
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