Hi Dan: I helped a blind ham friend get on the air from his apartment in
a 2 story building. He was forced to take down his trap vertical by the
management. We loaded the gutter system and he was able to operate with
no problem. You need to consider the gutter system as a random length
wire (sometimes called a Marconi). It is very important to load the
system against a ground or you will have all kinds of RF on your
transceiver case, microphone, etc. We chose a downspout near an outside
water faucett as the feed point. A wire was attached to the downspout
with a sheet metal screw and run under a nearby window to the tuner. The
wire had teflon spagetti around it where it went under the window. A
similar wire was attached to the water faucett and brought under the
window. If you have no faucett near the entry point, put in a ground rod
or lay some radials on the ground. A couple of radials @ 180 deg to each
other will work very well. Ideally these should be around 1/4 wave on
the lowest band but sometimes a compromise is necessary.
There is no way to predict the impedance of the antenna but it is
likely higher than 50 ohms and has reactance. I have had good luck
putting together a parallel resonant tuned circuit and tapping the ant
wire at various points on the coil while measuring the impedance into an
inductive link of a few turns around the bottom of the coil. The ground
wire, of course, is connected to the bottom end of the tuned circuit.
The variable cap is tuned for best match to 50 ohms. If you have a MFJ
259 or similar this can be done fairly rapidly. The ant wire should be
tapped as far up the coil as possible while still getting 50 ohms. This
widens the bandwidth and holds down the voltage across the cap. Good
Luck, Dan, N5AR
Dan Evans wrote:
>
> Hi All,
>
> As a temporary multi-band antenna, to get me through until spring when I can
> put up a small tower, I'm planning to use a tuner to load up the gutters
> [and trim] on my house. I live in a two story house on a small hill, and
> the house has 4 downspouts, one on each corner. Between the downspouts,
> running all the way around the eaves of the house, is an aluminum trim the
> gutters are attached to. I figure the circumference is around 150 feet, and
> the peak of the house is probably around 25 feet.
>
> I've read about doing this a few times, and even talked to a few stations
> that were doing it, but I've never tried it before myself. Anyone have any
> tips or suggestions?
>
> Thanks,
> Dan
>
> Dan Evans N9RLA
> 2015 S. Jimtown Ln.
> Scottsburg, IN 47170
> {EM78}
> 1/2 of the N9RLA /R no budget Rover Team
> Check out the Rover Resource Page at:
> http://www.qsl.net/n9rla
>
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