The variables inherent to antenna selection for the 160 and 80
meter band are few when you consider your location on Earth and how
much of it you have to work with. Commitment (read money) to the
band probably narrows it even further. Results can be confusing
when reading the past messages on "what's best". So in that vain
and 100 miles from the arctic circle I add even more.
160: Located far west of the HF towers is a full size 1/4 wave
vertical with 100+ radials on the ground. This antenna is made of
Rohn 25 with an insulated base and philly guys. The impedance is
from 28 to 33 ohms using three different instruments after waiting
for the local BC stations to shut down. I use a 50 ohm 1/4 xfmr and
complete the feedline run to the station with 75 ohm hardline. This
antenna was computer modeled before, during, and after
construction.
Another antenna for this band is an inverted vee. Its made of 3
wire 12 gauge copper clad steel with Hygain center insulator and
stainless hardware. The end insulators are 1 inch sq by 1 foot.
The 50 ohm coax is new RG214 double shield silver with silver
connectors and was thoroughly tested before installation. There is
one barrel connection at the base of the tower (electrical half
wavelength point) for impedance measurements. The antenna is bolted
to a 5 foot steel angle iron bar apx 180 feet in the air and 10
feet below a full size 3 ele 40 meter beam. The top two sets of
guys for the tower are philly. This antenna came within 15 Khz of
the model.
Results: The vee is down one or more s-units on all signals all the
time, everyday.
80: Located East of the towers is two 1/4 wave, 1/2 wave spaced
verticals running North-South. They each have apx 60 radials and
are fed in phase current forced. All normal constructions and
measurement techniques were used.
A second antenna for 80 is again another inverted vee. It is about
150 feet high with a 5 ele 20 meter yagi a few feet above it and
another 20 meter yagi 77 feet below it. There are 4 sets of guys to
two different guy points with a mix of philly and steel. This
antenna runs East-West above West running tower guys.
Results: The vee is always louder. Much louder on East signals.
Mixed results? Here's why:
Computer modeling shows the 160 vee doesn't have a chance. Even at
180 feet it is a cloud warmer. To make things worse the models show
the vertical field being clobbered by a 125 foot tower with
multiple ten meter yagi stacks located about 100 feet away. Last
summer I did a complete rebuild of this antenna to "mil specs". I
was concerned the antenna was electrically flawed and that might
explain its poor preformace last winter. It didn't. But it "looks
great" on the tower.
When an inverted vee for the 80 meter band is usually modeled the
results are somewhat dismal as compared to a regular dipole. But
few hams use them that way. Often they have yagis's above them and
guy wires around them. That may explain the "magic". A very high
vee for 80 seems to work well. I have tried to model mine and can
make it excellent to poor depending on how I adjust things. It was
easer in this case to build a dipole to compare. The dipole is
about 140 feet high and 175 feet away from the vee. It's running
North-South to work U.S. stations (East). The vee is running East-
West to work U.S. off the end (vertical). The vee is almost always
better 2 s-units or more. Going west the vee is above the West guys
and the dipole may be better depending on the time of day.
The 80 meter phased verticals also doesn't have a chance. Modeling
shows the pattern destroyed by guys North and towers West. They do
look good shimmering in the sun however.
Conclusion: Verticals need a lot of room. Cluttered antenna fields
give mixed results. A well enginered vertical in the clear will
outpreform low vees. A low vee is ANY inverted vee for 160 on
"amateur" towers. Water towers and USCG stations don't count.
Vee's for 80 meters that are high work well. An inverted vee may
have a "good/poor" direction because of the tower guys. A second
antenna often is necessary to confirm results. W2PV's 80 meter 4-sq
seemed to work well until he compared it to his 180 ft high
inverted vee.
On 80 meters the antenna selection is simply the high Yagi if you
have committment or anything else if you have the location. On 160
a phased array of verticals is the selection. The broadcast
industry has known that for 50 years. The rest of us of course will
place aside the law of physics and continue our search for the
magic top band antenna that will make us LOUD from a city lot.
The fellow who recently wrote "You can make anything work as an
antenna on 160, join the fun" operates from the East coast.
73 Rich KL7RA
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