On 5/21/2012 3:21 PM, Jim Brown wrote:
> On 5/17/2012 1:13 PM, Stuart Rohre wrote:
>> Jim I respectfully disagree, as I have seen examples of radiating
>> "ground" wires causing RFI.
>
> Since you didn't quote any part of an email, I have no idea what you're
> disagreeing with (or even whether it's me or another Jim that you're
> disagreeing with).
Maybe it just means you are just a couple
of "disagreeable fellers ..."
;-)
it can carry a lot
> of RF current if we allow it to become part of a transmitting antenna
> system. The most common way that happens is by using a long wire or
> vertical antenna and forgetting to provide a counterpoise for antenna
> current. When we do that, anything connected to the transmitter chassis
> becomes the counterpoise by default.
I know you did not intend these examples to be
all-inconclusive - I believe the comment applies
equally well to to the so-called or "end fed half-wave
dipole." The transmission line acts as a counterpoise.
W8JI agrees on his web site.
> Example -- back when I lived in Chicago, my shack was on the second
> floor, my antennas were bonded to a station ground, which was bonded to
> power, telco, some rods, and a big wrought iron fence that ran around
> the front of my lot.
* * *
The big #4 copper that
> ran from the second floor shack to those grounds and that fence WAS part
> of the antenna, even though it was CALLED a "ground" wire, and it
> contributed to the total radiation.
I thought a big cable running down from the second
floor would be seen as a high impedance thing to
a bolt of lightning... and was ill advised as a safety
ground. (Ignoring for a moment whether or not it
will radiate RF and act as part of the antenna system.)
Is that myth, or it is one of those cases where
something bad is better than nothing at all ?
==================== K8JHR ========================
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