"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.

Jack Painter
Virginia Beach, Virginia