At 05:32 PM 2/26/98 EST, W2GR wrote:
>Just curious if anyone might have any thoughts on any good 160 verticals.
> I saw the Gladiador in NCJ ...curious abt it.
Using Gladiators only, W1XT, operating in the Phoenix area,
medium soil conductivity, did the following during the ARRL
CW test last weekend:
160 meters....... 23 Q's/ 18 multi's
80....................... 76/34
40 .....................276/65
20...................... 271/77
15.......................192/63
10.........................58/32
Each band had it's own Gladiator monoband vertical, base elevated
about 10 feet on average, used only 4 elevated radials with each
antenna; each radial about 1/4 wave length.
Collected 916 Q's, 289 multipliers, and 792,438 points all with
these verticals over rather poorer soil: about 8 mS/meter conductivity,
that is, maybe a bit above average of other areas around the US
per ON4UN's book "Low Band DXing". He shows that about the
best in the US is in the area of the Great Plains, from Dallas on up
to about Lincoln, NE, where the conductivity is around 30 mS/meter.
By contrast, seawater is 5000 mS/meter! The higher the soil
conductivity out in the reflection zone, that is beyond the ends of
the radials by a wavelength or two, the lower the so called
pseudo-Brewster angle; the angle below which you do not radiate
much with a vertical.
Over very good soil (30 ms/m) the pseudo-Brewster angle at 3.5 mHz,
is about 3.5 degrees; this is the angle where the energy radiated
drops 4 or so dB below that radiated at the peak angle of 19 degrees,
then dropping gradually down from there about 3 dB at a
43 degree take off angle. Note also that these figures are all about
3 dB poorer than the energy radiated over seawater, because of
ground losses in the reflection (Fresnel) zone out from the antenna,
beyond the radial wire ends.
Over seawater, the psed-B angle is only about 0.1 degree, and the
peak of max radiation is at an angle of about 8 degrees, and is
down 3 dB from there at a 40 degree radiation angle. From the
North coast of Jamaica, the 6Y4A operation did outstandingly well
using only verticals, right at the edge of the sea; see Feb. and
March issues of CQ-Contest magazine.
So, Mike, have you any guess as to what your soil conductivity
is around your neighborhood? That will have a lot to do with how
well any vertical will perform, as long as you do put in a
decent radial system: either elevating 4 radials with the base
of the vertical well up from the ground, or dozens of radials on the
ground with the vertical ground mounted.
At least that is what I've learned from the ARRL Antenna Book
and ON4UN's book. BTW, Bob Meyers the builder of the
Gladiators has a web site for them, in case your are interested:
http://www.primenet.com/~bmyers/glad.html/glad.html
Incidentally, I have no interest in Bob's business, but am a customer!
And am impressed with what he did in the ARRL CW test with
those monoband verticals.
Is there a pattern of shift to verticals for DX, a la 6Y4A, see Feb.
and March CQ-Contest magazine.
73, Jim, KH7M
On the Garden Island of Kauai, where the Tropical Ag department
of the University of Hawaii claims that our typical agricultural
pasture land has a soil conductivity of 200 mS/meter! Also that
in the rain forests of Kauai, it decreases to around 100 (fewer soil
chemical ions), while some folks have trouble with their garden
lawns because the soil conductivity increases to 400 mS/meter or
so from added chemicals from constant watering with water
which has leached through the volcano induced chemical
rich soil!! At least that is the University's (Tropical Ag Deptmt's)
explanation.
Pasture land is watered by the frequent rains out here.
Have never heard of conductivty so high on the mainland that
the grass would not grow and stay green!!
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search
|