[mythtv-users] Antennas

Joseph Fry joe at thefrys.com
Fri Nov 15 17:23:44 UTC 2013


> My antenna (homemade) is supported by 3/4" pvc conduit, 3' into the
> ground and attached to the eave trough support and tethered with guy
> ropes. In windy conditions I have observed sway of 2", maybe 3" with
> little or no effect on my signal. I would bet your tree will have

PVC makes a great mast for a short period of time (maybe a couple of
years).  It becomes very brittle when exposed to prolonged UV light.
A coat of Krylon or similar paint helps immensely.

> greater sway, which is likely to have adverse effect for you. What
> happens when your tree grows and bursts your zip ties, or whatever
> fasteners you might use?

Last I checked, trees grow by adding layers to the outside, not by
expanding.  Typically a tree will simply grow around a fastener rather
than bursting it.  Though zip ties my still burst as most fare even
worse when exposed to UV.

Putting an antenna in a tall tree is actually a very doable solution
assuming you have a suitable tree.  You will still want a mast that
lifts the antenna above the foliage, and be prepared to adjust it
annually, but I know for a fact that many old HAM's and CB junkies
would do exactly that if they had a nice tall straight pine that was
easily climbed.

As far as wind causing swaying impacting your reception... I wouldn't
worry about it unless your in a deep fringe area, using a highly
directional antenna, where being a few degrees off will kill your
signal.  What wind may do is cause interference, and it won't matter
if your in the tree or not.  There are three known/assumed causes of
wind related interference.  First is that it increases scatter
radiation (weak signals reflected off leaves of other trees, etc)
which makes for an ever changing multipath signal that the tuner
simply can't compensate for.   The other is that wind may cause an
increase the amount of static buildup on your antenna/mast and other
surrounding surfaces; this buildup and subsequent discharge is what
some believe causes wind related dropouts.  Finally, when wind blows
it stirs up dust/pollen/water droplets/etc., even a small amount of
particulates in the air can impact reception.

I would say that if putting the antenna in a tree will give you line
of sight that you wouldn't be able to achieve with an affordable and
typical mounting solution , then put it in the tree.  Getting above
the treetops and achieving line of sight will help you more than
having an antenna that doesn't move at all but must penetrate trees or
rely on defraction/scatter to lock a signal... both of which would be
far more subject to problems with wind.  If you can simply mount the
antenna to your roof and have line of sight, than put it on the roof,
far easier to service there.

JUST BE SURE TO GROUND YOUR ANTENNA AND MAST!!!!


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