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A few weeks ago, I wrote a brief article on my attempt to build a beer
can antenna. In response to that article, I received several
suggestions about other homebrew antennas I might want to try. Among
them, the famous (or infamous, as the case may be) slinky antenna.
Since I have a son, it was a bit tough finding
the time to throw together this antenna without having to explain
why I was stretching his toys (I used three) to the limit, but
I finally got around to a preliminary version that actually does
a pretty decent job.
When I started looking into the possibilities of a slinky antenna, I came
across a lot of Websites and articles that claimed the whole idea
of a slinky antenna is just a myth. Countering these claims, however,
I also found a plethora of sites that described everything from a
simple antenna with just an alligator clip, to ones that went into
extensive detail about how to ground the slinky for optimum performance.
These days you can once again buy the original Slinky with the heavy,
bluish metal. Though most Websites repeat the figure of 80 feet
as the length of a slinky, the official word from Slinky Toys is "about
63 feet". As many of you may know, In 1945, Richard James (a naval engineer)
based the Slinky on a tension spring that he watched fall off a shelf
and "walk" on the floor. It seems that the first people
to use Slinkys as antennas were soldiers serving in Vietnam.
Right now, behind me, and over my shoulder, I have about 40 feet of Slinky
stretched through my apartment. I have one end of the Slinky fastened
to a tree outside my kitchen window. The other end is attached with an alligator clip to
the telescopic antenna on my Sangean 818. Since this a preliminary test,
just to see what kind of difference it might make, I've decided to
hold off on soldering the Slinkys together, and running a rope or
cable through the Slinkys.
My results have been mixed; probably because I'm keeping it very simple.
Still, as long as it wasn't bouncing in the wind or from someone
bumping into it and making it spring up and down, it did help me
bring in several German and Chinese broadcasts. These same frequencies
sounded like Charlie Brown's teachers without the Slinky so that
was impressive. On other frequencies the Slinkys seemed
to cause more interference than anything else - lots of static.
As with my beer can antenna, I am writing this article at an early stage
in the experiment. I would love to hear from any of you who have
used or seen a Slinky at work. It really is a fun, convenient antenna
that's easy to set up and put away. If kids are around, they might
be bothered to see toys stretched so far, and hung too high
above them to play with, but setting one up, even for the heck of
it, is a great way to teach them about the science of antennas and
radio.
Here is another link that has information on Slinky science:
Slinky, Clandestine Dipole
As always, please contact us with any comments or
article suggestions you might have.
Thanks for reading,
Carlos
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