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Fig. 10. Graph of wavelengths of feedline to
b.a ad;Jed to the top antenna in a stacking
situation (Fig. 9) for raising the main vertical
radiation lobe up to 30 degrees. This
will onlV work for 3N4 stacking spacing.
tance D is found to be .132 A. To simplify
things, this feed line difference has been
plotted in Fig. 10. Note that this is only
for a stacking spacing of 3/4 A.
A similar arrangement is being tried at
K9CSW, with calculated switch positions of
10, 15, and 20 degrees, but results are a little
hazy, Possibly the lobes are simply too
broad to make a noticeable difference when
shifted only a few degrees, Quads are partially
stacked antennas themselves, so elevating
the main vertical lobe any appreciable
amount adds importance to usually insignificant
side lobes. It's also quite difficult to
keep two quads looking electrically identical
for very long. One distinct advantage was
noted here, however, over simply switching
antennas. Some types of "city noise" apparently
arrive at very distinct angles; manipulating
the lobes in this manner often resulted
in noise reduction on the order of two
S-units. In some locations, this may be more
valuable than any outgoing signal strength
additions.
Conclusion - suggestions and more problems
The question I've still left partially unanswered
is exactly what are the best angles?
Bill Orr's Beam Antenna Book lists the range
of optimum angle of radiation as in Table
III. This is apparently inconsistent with
those findings by Utlaut, (see Fig, I) who
found the very best angle to be the lowest
tried, .7 degrees, much lower than the
supposed 7 degree minimum. This was in
light of the fact that the transmitting antennas
in this case utilized realitively high
angles (I2 or 16 degrees) for main lobes.
Although only listed for four months,
Utlaut' s signal strength versus time averages
do sho w definite seasonal variations; low
angles did seem valuable during a summer
month (June or July) when the rule seemed
the lower the better for the time the band
was open. The spring months, however,
pointed out the advantages in ability to vary
the radiation angle, since higher angles dominated
for much of the "band open" time.
Results at K9CSW have varied, but seem to
agree with this trend. Certainly an accurate
yearly pattern could be worked out for a
particular DX path, but the effects of other
phenomena (sunspot number change, ionospheric
storms, north-south tilts, etc.) that
may be encountered along the variety of
paths a DXer is interested in would make the
game quite involved.
Band
Range of Optimum
Angle of Radiation
"Optimum" Antenna
Height
7me 12 °-40° Above 45'
14 me 10° - 25 ° Above 40'
21 me 7 · - 20· Above 38'
28 me 5 0 - 14 0 Above 34'
Table III. Geometrically determined " conmum"
radiation angles for the ham bands. (4)
Another problem was encountered at
K9CSW. Although signal strength differences
were sometimes reported in excess of two
Svunits for one angle over another, it was
rare when a same difference was noted on
received signal strength. Apparently many
DX paths are not completely reciprocal. This
is a good thing or we might have to worry
about accurately matching the DX station's
vertical radiation pattern, but adds to the
confusion when trying to decide which angle
to use to be heard the best. Even in cases
when signals received on both ends were
enhanced, the difference was usually not
detectible unless two-way key down S-meter
tests were run. In contests or chasing a
DXpedition, these key down tests are a little
hard to come by; the need for some sort of
system is apparent. Since accurate angle of
arrival measurements are expensively complicated,
perhaps only trial and error can devise
such a system. It's hoped, however, that
such a system actually exists, for it could
payoff in great dividends for the serious
operator, greatly adding to the effectiveness
of even a modest antenna,
. . _K9YOE
R~ferences: .1. Davies, Keooeth. Ionospheric Radio
Propeqetion, (Washington, D .C. U _S . Government
Printing Office, 19651. Ch . 4 . 2 . trrteue,
W .F. " Effect of Antenna Radiation Angle Upon
HF RadioSignalsPropagated Over Lon~ Distances,"
Journal of Research of the NBS-SectIOn D . Radio
Propagation, (Volume 65D, March·April 19611.
167-174. 3 . The American Radio Relay League.
The ARRL Antenna Book, (West Hartford, Connecticut:
ARRL 1956) Ch . 2 . 4 . Orr, William I­
Beam Antenna Handbook, (Wilton, Connecticut;
Radio Publications, l nc., 1955) Ch's. 1 & 6 .
MA Y 1969 83