[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Cheap LEO antennas



Those of you who would like to have an Arrow antenna, but are a bit short of
radio money should get a copy of the Summer 2006 issue of CQ VHF and read Kent
Britain's article on "Cheap Antennas for LEO Satellites".  Having built several
of Kent's Cheap Yagiis for 144 through 1296, I am convinced that if you follow
his instructions and work carefully you will get a good antenna very
inexpensively.  Based on my experience with these antennas, there are a two
comments I would like to make.

Kent mentions varnish as a good boom coating if you are going to mount the
antenna outside for a long time. Varnish, Spar Varnish or Polyurethane do not
contain adequate uv protection and deteriorate in only a year or two.  I built a
144 yagii and a 432 yagii and applied two coats of Polyurethane to the boom. The
antennas were mounted on a mast temporarily until I could afford a metal
antenna.  Two and one half years later in the upstate NY weather, the antennas
still worked well, but the 144 antenna had developed a twist.  Taking them down
for inspection showed that the polyurethane was almost non-existent, allowing
moisture to get into the boom and warp it.  If you plan on leaving  the antenna
out in the weather, cover the boom  with a couple of coats of exterior house
paint instead of varnish.

Kent suggests Aluminum ground rod wire, #10 copper wire, bronze welding rod, and
hobby tubing as element materials.   He also suggests that these antennas will
be stored in the garage, the back of your car, or the back of your truck, to be
taken out when you go satellite chasing.  My 144 and 432   "cheap yagiis" are
stored in a rack in the back of my truck. and taken out, mounted on the tripod,
removed from the tripod,  and returned to the rack whenever I go satellite
chasing. During this process an element  will often hit something.  My
experience has been   that aluminum and copper wire bend very easily whereas the
welding rod usually springs back. The aluminum and copper elements bend back
easily, assuming you remember to do it, but they are never  as straight as they
originally were.  The only problem I see with the welding rods is the need to
splice them with brass hobby tubing and the 180 degree bend in the driven
element.  Making this tight bend in welding rods will cause the rod to break
unless you use a torch to heat the area you are bending.

I expect that before fall arrives, I will build one of the LEO antennas and have
the additional fun of using an antenna I  built myself.

73 de WB2LLP   Gene
----
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home