3217RE: [ScoutRadio] antenna mounted on sand
- Jan 3, 2009at the airports try using sandbags made out of old innertubes. just zip tie the ends closed or use the aircraft tie down points there in bedded in the concrete they should be all over the ramp. I work at an airport and 25 years air force/ air guard... 73 . mike ke7ytm former kd7sgy
Date: Wed, 31 Dec 2008 22:25:55 -0500
Subject: RE: [ScoutRadio] antenna mounted on sandOn sand, the challenge is to keep the "tent" pegs from pulling out. May I
suggest a "dead man" similar to what one would also want for snow...
I also use a mount for my vertical antenna made out of 1/2" x 4" steel
welded into three flat legs about 15" long. It weighs 15-20 pounds and has
a vertical angle iron 12" high welded to the base that I hose clamp my 32'
fiberglass mast. As long as there is no wind, it will self support.
A steel wheel (truck) would work, too.
73, Steve KB3NCC
From: ScoutRadio@yahoogro ups.com [mailto:ScoutRadio@yahoogro ups.com] On
Behalf Of n5gui
Sent: Monday, December 22, 2008 10:04 PM
To: ScoutRadio@yahoogro ups.com
Subject: [ScoutRadio] antenna mounted on sand
The recent discussion about setting up an antenna, particularly the
leave no trace angle, reminds me of a thought experiement that I did
a few years ago.
To set the background, I have been a tinkerer on portable antennas
and mounting structure for a few years. My first success was three
monoband verticals, 20M, 15M, 10M, used by the Wichita Amateur Radio
Club (WARC) for Field Day 2000. Each was a "ground plane", that is,
quarter wave vertical with four quarter wave radials, using seven
strand antenna wire for the electrical elements and PVC pipe for the
supports. The radial wires were included as part of the guy lines.
The particular design was chosen for omni-directionality and 50 ohm
feedpoint (adjustable by changing the droop angle of the radials).
The 10M and 15M antennas were fed at 30 feet, making them about 39
and 42 feet tall respectively. The limitations of my skill and of
the PVC pipe in the Kansas Summer Sun required that I feed the 20M
antenna at 26 feet resulting in an overall height of 43 feet. I got
lots of practice at launching the antenna, so it took me about ten
minutes to set each up. However, I had a conflict on Field Day, so
I invited some of the club members over to teach them enough to
launch on their own. Which also confirmed that it is easier to do
with a crew of three to five.
As I said, these were successes in that the club could set them up
without my help and they performed about as well as the dipoles that
were strung in the available trees. Success was followed by
additional opportunity. However, opportunity often comes with new
challenges. I needed to provide antenna support for a commercially
made multiband ( 160M - 10M ) dipole. I soon found that I had to
abandon the PVC pipe for steel poles, later replaced with aluminum.
Now I routinely provide a 38 foot mast for a 2M colinear vertical or
three 30 foot masts for a multiband dipole.
There are still challenges to meet: Kansas provides lots of open
grassland where I can drive the necessary stakes, leaving little or
no trace after after a rainstorm and lawnmower. However, I still
haven't solved the problem of safely setting up my antenna masts on
a sea of concrete typical of an airport taxiway. In a parking lot I
could just park cars in the places I needed them for a few hours.
Airports, at least the military ones, don't want a lot of casual
automobile traffic mixing with the airplanes. I did come close with
plywood and bricks..... If I only had more bricks...... ..
The concrete problem got me to thinking about a "universal
solution", which would serve on grassland, concrete, or sand. The
sand problem was particularly interesting to me. As I boy I had
been to Padre Island along the Texas shore. I thought that would be
an interesting place to camp for a week or so. Miles and miles of
sand. No trees. Hardly any grass.
Maybe some Scouts would find it an interesting challenge to set up a
HAM station on a beach. I am focusing on the antenna supports, so
here is what I suggest: Three 30 foot poles to support a dipole at
least 100 feet long. If you want a little more challenge, use
schedule 40 PVC pipe as the primary material. It should be less
expensive to work with, and a little more forgiving of bends or
drops. The skill and equipment needed to build the antenna supports
should be within the capabilities of most Scouts.
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