At 2:55 PM -0800 12/31/02, Thomas Beltran wrote:
>I put up a dipole, 194 feet long, fed with Ladder-line, which then
>goes to a W9INN balun, which goes to about 22 feet of coax into the
>shack. I have
>the balun grounded per its instructions.
All this sounds good to me. I don't know the W9INN balun, but I'd
follow the manufacturer's instructions (the Towertalk Prime
Directive). Grounding the balun may help to divert common-mode
current from the coax; it may also help to ensure that both halves of
your dipole are DC-grounded; it may also help to protect your house
and radio/electronic gear from lightning. All Good Things.
>Several people sent me off-line emails saying one does not need an
>RF ground. I guess back in the late '60s when I started in this
>hobby, the watchword was always that one needed a good ground. Tom
>W6EIJ
In the old days (I've been licensed since 1956), unbalanced antennas
and unbalanced feeds were more popular. E.g., my first antenna was a
Windom fed by a single wire. With such antennas, an RF ground was
mandatory -- no question!
Also in the old days, ferrite-core balun transformers and common-mode
RF chokes were unavailable; and transmission-line baluns for low
frequencies are impractically long.
Unbalanced antennas driven with respect to "ground" (earth, seawater,
or counterpoise) were made popular by Marconi. For the low
frequencies that were utilized in the early days of radio, unbalanced
antennas were best. Even today, for 160 meters, an unbalanced
antenna is probably best, unless you can support both ends of a
balanced antenna more than about 100 feet above ground. What's best
for 80 meters is more debatable, and IMO the answer depends on what
kind of ground is available at your QTH. In New England where soil
conductivity is low, balanced antennas work better. But for 7 MHz
and up, almost everyone is better off using balanced antennas.
Not only is a balanced antenna a more efficient radiator, it is also
quieter for receiving. However, for it to be quiet, you must not
conduct noise to it from the AC power line in your shack. An AC
power line is _incredibly_ noisy. Therefore you need many, many dB
of isolation between it and your antenna. This fact is not
appreciated by most hams.
-Chuck, W1HIS
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