On Oct 13, 2005, at 9:03 PM, Bill Turner wrote:
> At 01:51 PM 10/13/2005, monty taylor wrote:
>
>> As a result I will RF ground outside my
>> windows today as I already have the 8 foot rod ready to go.
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> I shake my head whenever I hear the term "RF ground" in the sense of
> running a ground wire to "get rid" of stray RF. Here's why:
>
> 1. You can't simply run a wire to "ground" RF in the first place.
> That ground wire you are installing is a significant portion of a
> wavelength at HF. On 10 meters, for example, an eight foot wire is
> approximately 1/4 wavelength. If it is "grounded" at one end, the
> other end is an open circuit. You have "grounded" nothing at all. At
> lower frequencies, the effect is less pronounced because the portion
> of a wavelength is less, but that ground wire never completely
> "grounds" your equipment.
Well put, Bill.
>
> 2. Even if you could "ground" your stray RF, why should you? RF
> energy is expensive to generate. Do you really want to run that
> expensive RF energy into dirt? Does dirt help your signal?
With a Hertz antenna (end-fed half-wave) ground loss is a factor --
albeit a small one.
>
> 3. When you have RF in the shack, you do not have a grounding
> problem, you have an antenna problem. Almost always, the source of
> the RF in the shack is unbalance in the antenna system (including the
> feedline), and that's what you should be fixing, not "grounding" the
> RF to get rid of it.
Amen
>
> 4. For coax-fed antennas, the easiest cure in nearly all cases is to
> install a 1:1 balun in the feedline, usually right at the point where
> the coax connects to the antenna.
A coax-choke balun (a.k.a. "Ugly Balun") at the center feedpoint of a
dipole fixes this problem.
> It is also possible that the
> physical layout of the coax is causing unbalance by picking up part
> of the antenna's field on the coax shield. Relocate the coax so it is
> physically balanced with respect to the antenna.
>
> For those of you who'd prefer to go on "grounding" your RF, I hope
> you have lots of patience in the pileups. You'll be needing it. :-)
chortle
>
> 73, Bill W6WRT
>
>
>
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>
Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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