Trees and Reception
A common call that we get will go something like: “Reception is great unless the wind is blowing, then we get
constant breakups, dropouts, or freezes. What’s wrong with the antenna?” The answer is that nothing is wrong
with the antenna itself, the problem is that the antenna is behind trees. When the trees move, they block and
distort the incoming signals so that the TV tuner cannot make out the signal properly and reception fails.
What causes this?
As far as the TV signals are concerned, the area behind trees could best be called "dynamic chaos". Think of a
stage curtain made from strips of both reflective and opaque strips. Turn on a fan and a spotlight and try to see
what is behind the curtain. Your ability to see what is behind this curtain mimics the ability (or lack) of the
antenna to "see" the incoming signals.
Every leaf, twig, branch, limb, and tree truck will have some effect on the incoming signals based primarily on
their moisture content. The higher the frequency (channel) of the incoming TV signals, the more pronounced the
effects. The effects may vary even within a single channel’s bandwidth. UHF stations are most affected, more so
than high VHF stations. Low VHF channels 2-6 are least affected. With about 75% of US stations operating on
UHF channels, it can be seen that this can be a common situation.
When the wind blows, the physical pattern of the leaves, twigs, branches, and limbs will change, the resulting
signals fields will change, and the tuner's error correction circuits have to go to work. If they are overwhelmed,
reception errors will be apparent as anything from mild errors to a complete loss or absence of reception based
on the quality and strength of the incoming signals. Every variation of wind and moisture will cause reception to
vary by introducing both signal loss and complex multi-path reflection. Some folks have little to no problems
with tree-blocked reception (they're the lucky ones) while others will have a wide variety of reception problems
from mild to severe.
Unfortunately, there's not a lot that can be done from the antenna side of the equation to solve these problems.
Sometimes a two antenna system with an A-B switch can be used to optimize reception of various stations for
different times of year and different local conditions. An amplifier might help a bit by shifting the signal into a
"sweeter" spot in the tuner's adaptive equalizer performance band, but the effectiveness is often highly
variable. Sometime it helps, sometimes it doesn't. Think of it this way: Put your paycheck through a paper
shredder. Now, attach a large magnifying glass to the heap and try to cash the check. If the bank can't read it,
they won't cash it. All the magnifying glass did was to make the shredded pieces look larger. Likewise,
amplifying a distorted or "shredded" signal makes it "bigger", but not "better".
Selecting the best mounting location is preferred. A mount that puts the antenna above the trees is best, but is
expensive and not always feasible. Tree trimming or removal, if possible, may be required so as to provide a
path for the signal to get to the antenna. But, sometimes, you're just plain out of luck despite your best efforts.
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