RadioBanter - View Single Post

[email protected] · January 20th 15, 06:30 PM posted to rec.radio.amateur.antenna

wrote:

snip

A vertical generally needs radials unless it's a "1/2 wave" type
design. And even good verticals can be quite lackluster for close
in work compared to a low dipole on 40m. Good at night to DX though.
But like I say, he's gotta decide what he wants to concentrate on,
and go from there.

You are all over the place here and mixing apples and oranges.

A vertical has a low elevation angle.

Any antenna that has a low elevation angle is "better" for distant
communications than an antenna with a very high elevation angles.

A horizontal antenna less than a half wavelength in height has a vey
high elevation angle. At .3 lambda it is 48 degrees, at .25 lambda
it is 62 degrees, and at .2 lambda it is 90 degrees, i.e. straight up.

This is called an NVIS antenna which is "better" for local communications
out to about 500 miles or so on the lower bands. NVIS communcations is
nearly nil much above 8 MHz at other than sunspot peaks. We are currently
past the peak of the current sunspot cycle and heading for a minimum.

A vertical antenna does not "need" radials, but it's performance is
improved by radials.

A vertical antenna over average ground has a main lobe at about 30 degees
and a gain of about 1 dBi.

A vertical antenna over perfect ground has a main lobe at 0 degrees and
a gain of about 5 dBi.

In a typical urban setting where there is landscaping and irrigation,
the ground is most likely average to very good unless you are in the
middle of a desert, which means even without radials the vertical's
gain is going to be a few dBi. Adding a few radials will improve the
gain and lower the main lobe but are not absolutely necessary.

Most verticals will get put in the middle of a lawn and it is trivial
to take a lawn edger or weed wacker and cut a groove in the grass down
to the dirt and staple down some radials. In such a setting you do
NOT need the 120 radials of a commercial broadcast station with it's
antenna in a barren field.

If he has trees to tie dipole legs to, he really only needs one
support for the apex.

The bottom line is a horizontal antenna needs three supports.

snip

And the tuner/ladder line fed dipoles is another option if one wants
all bands with one antenna.

As is a vertical piece of aluminum tubing of whatever height you can
put up with an ATU at the base of it.

--
Jim Pennino