Steve Reinhardt wrote:
I'm looking at another antenna for 20M. I've got a partially folded
indoor attic antenna which gets out fairly well, but it certainly is
directional.
The ARRL handbook has had this design in it since they invented radio.
It's often used at VHF, but seems a good candidate for this QTH. It's a
1/4 wave element over 4 1/4 wave radials at 45 degrees off horizontal,
drooping to earth. My installation would be at ground level, with the
base of the radiating element about 12.5 feet of the earth.
Mechanically, it would be easy to put together, but I hate to waste
the time if it's known to be a poor performer. I tried to use the EZNEC
4 demo, but 55 segments aren't enough to create a reasonable model of
the physical layout, and I'm not smart enough to try a simplification.
So, has anyone done an analysis of this antenna? Would the performance
be similar to a low mounted vertical dipole, or would the 4 radials
offer a bit better performance so close to earth?
If there's an literature I missed, please point me toward it. Most of
the antenna manufacturers refer to regular flat, on the ground radial
systems, and except for some CB literature which has no technical basis
for its recommendations, there's not any analytical data I can find. The
best thing I found was at web.wt.net/~nm5k/acompari.htm for 10m
applications, at 40 ft elevation.

73,
W1KF
Steve

Why not look at the shortened vertical Dipole. Theres some construction
details in the 2006 Handbook.

Another good antenna is the Skeleton slot. Fed with open wire feedline
makes a good multi band low angle radiator.


Placing any vertical antenna high as the cb'ers do is just a waste of
good RF energy. You split the main lobes and get a lot of high stuff.
Which may be good for local stuff.

4 radials closes to earth might work if you have good earth
conductivity. Otherwise you will be losing a lot of your power heating
the earth.

A vertical on the ground needs 60 radials to be competitive with a
good dipole at 40 and above feet.

A vertical fed with high power works because its take off angle is
close to ideal as a general purpose DX antenna. I can thrash guys on 20
meters running low beams with a good vertical! Some just dont understand
how circuit gain is affected by takeoff angle. Its the difference
between the positive and negative gain on both ends this can amount to
10 to 20 db at low angles. Something guys with stacked yagis know of
very well.

If you soil conductivity around you is poor there no advantage to using
a longer vertical. Your take off angle is determined by the brewster
angle. The longer you make a vertical the better the ground system you
must have and further out it must be to prvent losses. In restricted
neighbourhoods its a waste of time!


Just operating in a urban environment with a vertical your signal will
be down 6 db over that same vertical in a open area. Urban areas have a
built in loss factor, this has been documented by the ITU. I sit on the
edge of urban sprawl and can kill stations with low yagis with a good
ground mounted vertical just because i am in the clear.


But suck it and see, try it. It does not cost much. Vertical antennas
are not inherently noisy in a quite location. Its just when you use a
vertical antenna in urban areas most of the major is intersecting and
passing directly through the noise source, so it seems noisier. Try a
vertical antenna in the country and compare it to a dipole they have
about the same signal to noise ratio.

My 2 Bits worth

Greg