On Sat,2/20/2016 6:15 PM, Gerald Wolczanski wrote:
Jim, I totally understand antenna return currents in an unbalanced
antenna....having once built a vertical with 110 radials.
Even a dipole center-fed with two-wire line can be unbalanced by its
surroundings, and even with a "balanced" tuner. Balance is defined as
impedances in the system being equal to the reference plane , NOT by
voltages or currents. Indeed, voltage and current imbalance is the
RESULT of imbalance in the system, which includes the antenna (and its
surroundings), the line, and termination of the line in the shack
(including a tuner or other matching network).
My current 135' end-fed inverted-L is a superb performer with my fan of
radials laying in the backyard.
I have a Tee vertical for 160M with a bunch of radials, and it works
well too,
So let me ask a practical question:
Can I attach my radial system (which I would disconnect from the copper
pipe driven into the ground) to my L-network coupler and ISOLATE THAT
COUPLER FROM GROUND WITH A BALUN?
That is a bad idea.
That would separate the RF ground from the Shack (lightning ground).
That's also a bad idea. Remember that lightning is NOT a DC event, is
an RF event, with peak energy broadly centered between about 100 kHz and
10 MHz. A radial system provides capacitive coupling to the earth, so
if it's part of the building ground, it lowers the impedance to earth,
so it improves lightning protection.
Second, there is no such thing as RF ground. For decades, we have heard
the same nonsense from the high-futility audio world about separating
the "clean audio ground" from the rest of "ground," which is "dirty."
Separated grounds are a really bad idea, especially at RF. Now, we DO
use "isolated ground" wiring in power systems in buildings to minimize
circulating noise currents on sophisticated technical systems, but every
part of those systems IS grounded and bonded in a very well controlled
way, and all grounds are ultimately bonded together.
73, Jim K9YC
BTW, I have a spark-gap lightning arrester outside my shack window.
Thanks
Jerry
KI4IO
Warrenton, VA
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