Friends in Radio Land -
With the recent discussion about magneto-ionic power coupling
and the present interest in the K1B DXpedition, I have calculated
the insertion loss to and from the lower ionosphere at K1B using
data obtained from the International Geomagnetic Reference Field
(1990).
K1B is at a low latitude where the field is within 2 degrees
of being horizontal, much like the situation at Togo during the
5V7A DXpdedition that I mentioned in a recent posting. The data
given below shows the large (>10 dB) insertion loss for E-W
propagation with a vertical antenna. In that regard, it would be
of interest to examine the K1B 160 meter logs to see the extent
to which E-W propagation was affected.
With a high dipole oriented in the N-S direction, the loss
would only be about 0.2 dB in the E-W direction. But a high
dipole oriented E-W would be as effective in the N-S direction
(about 3 dB loss) as a vertical antenna as the horizontal
geomagnetic field presents the same aspect to both horizontally
and vertically polarized waves from the antennas.
Again, a detailed discussion of power coupling is to be found
in the Spring 1999 issue of the Communications Quarterly.
Power Coupling Loss for K1B
O-Wave, 20 deg rad angle, vertical antenna
Heading Loss Heading Loss
degs E of N (dB) degs E of N (dB)
000 - 015 -2.8 180 - 195 -2.8
015 - 030 -2.9 195 - 210 -2.9
030 - 045 -3.1 210 - 225 -3.1
045 - 060 -3.5 225 - 240 -3.5
060 - 075 -4.3 240 - 255 -4.3
075 - 090 -5.9 255 - 270 -6.1
090 - 105 -10.7 270 - 285 -12.0
105 - 120 -14.6 285 - 300 -14.3
120 - 135 -6.3 300 - 315 -6.3
135 - 150 -4.1 315 - 330 -4.2
150 - 165 -3.2 330 - 345 -3.3
165 - 180 -2.8 345 - 360 -2.8
73,
Bob, NM7M
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