Since the run is about 30 feet, make it 33' or 32' if it's not bare. And use
up the extra length by not making square turns anywhere. Don't put sharp
bends in the wire if you can avoid it. You *may* create the appearance of a
low z path on 20 and up. 30-ish is going to look hi-z on 40 no matter what you
do. Otherwise, what Gary says...
73, Guy.
----- Original Message -----
From: "K9AY" <k9ay@k9ay.com>
To: "Howard W3CQH" <hsgorden@comcast.net>; <antennaware@contesting.com>
Sent: Monday, April 21, 2008 10:41 AM
Subject: Re: [Antennaware] Grounding needs
>I live in a 1 story home with a accessible attic.
>
> I have an Icom AH-4 tuner mounted in the attic, and need to run a real
> ground to the 8' ground rod we just pounded in.
>
> My question is - should the ground wire coming from the AH-4 be of a wire
> gauge of #12, or should I consider running 1/4" copper tubing? The total
> length of the run is approximately 30'
>
Howard,
At a length of 30 feet, there is no RF "ground" -- it's nearly 1/4
wavelength at 40M and will always be part of any antenna connected to the
attic-mounted tuner. If you include the ground wire in a computer model of
the antenna, this will be quite obvious. I have three suggestions:
1. Install the ground wire as short as possible, with as large a conductor
as is practical. If the tuner and antennas work as you expect, you are
finished.
If the antennas fail to perform as expected, or if the tuner behaves
erratically, the new wire has created an unwanted resonance and/or increased
the RF levels at the tuner. One of the two other options may work:
2. Add an RF choke in the power/control wires of the tuner -- ferrite beads
or a few turns of all wires through a large toroid. This will "disconnect"
the wires at RF.
3. Run multiple ground wires (e.g. 3) of different lengths to different
ground rods. This will create different RF paths with different resonant
behavior. Odds are that this will change things enough to reduce the
problem.
73, Gary
K9AY
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