"starman" wrote
Jack Painter wrote:

"starman" wrote
Jack Painter wrote:

"starman" wrote

A low noise inverted-L will have the vertical downlead at the far
end
of
the horizontal section with the balun located at the lower end of
the
single wire downlead, near the ground. Then you can run coax back
to
the
house from the balun. The near end of the horizontal section
shouldn't
be too close to the house where it might pick up noise.

The 'low noise inverted-L' (paragraph above) can make a big
difference
in lowering the noise that the antenna picks up from local
sources.


There is not one ounce of truth to an "Inverted-L" being ANY quieter
than a
45 degree random wire, and especially a horizontal-dipole, which is
generally quieter than any antenna with a vertical component. Most
interference is vertically polarized, and the verticals,
random-wires,
slopers, or inverted-L antenna designs all pick up more vertically
polarized
"noise" than a horizontally polarized antenna. Adding a vertical or
even
a
45 degree sloped component to an antenna DOES make it less
directional
than
a horizontal, and that is all it does. Any noise-limiting realized
from
these designs comes strictly from the grounded-Balun and not the
design,
configuration or dimensions of the antenna. Shield-grounding (for
static
and
lightning protection) at the feedpoint will achieve 99% of the
noise-limiting benefit that a grounded Balun does. The missing 1% is
an
equal loss of signal and noise through the Balun. All RF noise (but
not
all
energy has RF components) is coupled right across the Balun
windings,
their
function of electrically decoupling is true of some DC energy, but
not
RF
energy, which is rather efficiently coupled across the Balun by
design.

The same application of a grounded-Balun works equally well on both
the
random (straight) wire antennas and inverted-L antenna btw. Both
the
random
wire and inverted-L benefit from (require in most cases) a
counterpoise
ground or radials to provide effective transmitting. Neither a
counterpoise
nor radials affect reception from the either the random wire or
inverted-L,
however.

I think you've missed the point. A so called 'low noise' inverted-L is
intended to reduce noise on the feed line to the receiver which comes
from domestic sources like appliances in the home. This is not the
same
as the noise being received by the antenna wire itself. When the feed
line is part of the vertical section of the antenna, like the typical
inverted-L or random wire, it can pick up noise from the domestic
environment. The solution is to use a coax feed line which connects to
a
balun near the ground. The vertical section of the antenna comes down
to
the balun. This allows for a short RF ground from the coax shield to
earth which decouples the noise on the shield.

Well I didn't mean to miss the point, and I'm afraid you're far off base
in
suggesting that an inverted-L radiates part of the feedline or that
feedline
(coax-shield) noise has anything to do with an antenna configuration.
The
use of coax minimizes feedline noise, and shield-grounding the coax
further
reduces noise from either being brought into the shack or carried to the
antenna from the shack. In an inverted-L, either a Balun or a choke is
always used to prevent inadvertent feedline radiation. The vertical
portion
of the end-fed inverted-L is where the feedline ends and the antenna
begins.

The real noise-limiting design of any beverage-style or inverted-L wire
antenna is to ground one half of the Balun output. This is whether the
coax
shield is grounded earlier or not. That does affect signals picked up on
the
antenna wire itself, although experts are not agreed as to whether there
is
a measurable improvement in signal to noise ratio as a result of this.
As
Telemon mentioned, having a counterpoise or good RF ground could make a
difference there. In my particular case, there is a marked improvement
in
signal strength and possibly some reduction in noise when the connection
from ground rod to Balun is made. I also transmit through this antenna
with
pretty good results. The original concept of grounding one-half of a
current-type wire-fed Balun for noise limiting came from an 1980's issue
of
Fine Tuning's PROCEEDINGS. I was borrowing the issue from a friend and
cannot remember the original author of this but I don't believe it was
the
venerable John Doty to which it is lately accredited.

If the coax shield of an inverted-L does not have a good RF ground,
which requires a short ground wire to earth, the domestic noise on the
shield can couple to the center conductor of the coax where it connects
to the antenna. The noise will then become part of the antenna signal to
the radio. That's the point I think you missed.

OK I didn't restate the obvious, agreed.

The best place to terminate the antenna and mount the Balun is *at* the
ground rod, which means the connection is about 4 inches long. Ty-wrap the
Balun to the protruding ground rod. After applying coax-seal to the
wire-wrapped and then soldered connections, cut the bottom and slit one side
of a plastic beverage bottle to just fit over the Balun and tape the bottle
shut afterwards. Spray paint the bottle with bow-flex cammo and it becomes
part of the background, and weather-proofed for years of service. Some
designs advise terminating the vertical drop of the inverted-L about 6 feet
above ground. That's more important for a center fed or off-center fed
(dipole type) antenna than the end-fed wires. Users should have no problems
terminating the inverted-L at ground level, and sink a good ground rod (with
buried radials if you desire) at that same point.

Jack Painter
Virginia Beach, Virginia