The downspout has a vertical run
of about 16 feet, connecting the horizontal rain gutter which
is about 16 feet long across the front of the house. Including
the feed wire into the shack, the total length is in the neighborhood
of 42 feet; over a quarter wavelength for 40 meters and almost a half-wave for 30 meters.
The house is made of brick, so the entire system is isolated from
ground.
I use
my downspout like a random wire antenna, using a commercial autotuner (or internal tuner, in the case of my KX3). I
feed the antenna through a homebrew 1:1 unun.
I use a short run of coax between the unun
and the autotuner on my operating table. A length of #22 stranded
hookup wire is used to connect the output
of the unun to the downspout outside.
To
connect the wire to the downspout, I first sanded the downspout
and connected the wire using three sheet metal screws. I
used multiple screws to help ensure a low resistance connection.
After making the connections to the downspout, I sealed them up
using an adhesive/sealant called Goop. Goop is available
at most hardware stores.
With
the downspout behaving essentially like an end-fed wire, it really
helps to work this type of antenna against a good ground. Fortunately,
my basement operating position is only a few feet away from where
the water supply pipe enters the house. I used a piece of 1/2-inch
copper pipe as a ground bus between my operating position and
the incoming water pipe. A tinned copper braid strap and a couple
of ordinary automotive hose clamps were used to connect the bus
to the water pipe. A short braid strap connects the ground stud
on the unun to the copper ground bus.
For
good measure, I attached counterpoise wires to the ground stud
of the unun; one each for 40, 30, 20, and 15 meters. The counterpoise
wires are made from garden variety stranded hookup wire cut to
a quarter-wavelength. I just run these wires around the shack,
hiding them under the rug. Operation on the 80 meter band has
been successful using just the ground bus.
How
well does it work? During the first few months of operation, I
worked 49 states; all with 5 watts or less. I've also worked a
bunch of DX stations (though I'm more of a casual rag chewer than
a DX-chaser).
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The
length of the "antenna" is somewhat short for 80 meters,
but performance on that band has been a big surprise. Signal reports
on 30 and 40 meters, my primary bands, have been consistently
good. In fact, the downspout has been my main antenna at home
for more than 20 years.
While
this arrangement has served me well, it is not without an issue
or two. I find that it helps to clean up and re-do the connections
at the downspout periodically. Typically, I do this maintenance
every other year or so. Also, I have noticed that my local
noise levels on 80 and 40 meters have steadily increased over
the years. I attribute this to the proliferation of electronic
gadgets both in my house as well as my neighbors' houses.
Those bands are still usable, though.
Some
words of caution are in order, however, if you plan to use your
rainspout as an antenna:
Make
sure your gutter and downspout are isolated from ground.
Make
sure there is solid electrical continuity between the various
sections of your downspout and gutter. Mine are fastened with
pop rivets (not the greatest for RF work, but they appear to be
doing the job.)
Watch
your power. I wouldn't recommend running a kilowatt into your
rainspout. Ham radio is fun, but not worth burning down your house.
Make sure people and pets won't come in contact with the "antenna"
while you're transmitting. This isn't too much of a problem at
QRP power levels, but be careful.
So,
if you find your HF antenna options are limited by either space
or legal restrictions, take a look at the outside of your house.
There just might be a free multi-band antenna hanging out there!
72, Craig
WB3GCK
References
1 The WB3GCK Downspout
Antenna
http://www.qsl.net/wb3gck/spout.htm
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