Topband: "Bang" per kW

by way of Bill Tippett <> Nm7m at
Sat Dec 31 08:33:58 EST 2005

In this age of globalization, DX contesting has become more
competitive, no doubt about it.  Contesting on 160 meters is
inherently different as the geomagnetic field has a measure of
control, by how its strength and orientation vary with location.
Thus, operators in mid-latitudes have an advantage over those at
low latitudes, just because the field is more vertical there and
provides a better polarization match with vertical antennas.

While it can be worked out in detail, comparing W1's with W6's,
it is of more interest to make comparisons by regions of DX
activity.  So, using magneto-ionic theory, I have worked out the
amount of power per kW ERP that goes into low-loss O-waves in
the ionosphere for various DX directions, e.g., 750 W/kW for a W0
calling a PY.

In the Table below, the targets are listed in the top horizontal
row and the other horizontal rows show how the power at a given
location is transferred to the ionosphere as O-waves by a vertical
antenna.  The difference betweeen those numbers and 1000 W goes
into high-loss X-waves which are rapidly absorbed and contribute
only to global warming, not DXing.

Power transfers for PY are much lower than the others as the field
in the South Atlantic Magnetic Anomaly is close to horizontal,
giving a large mis-match with the vertical antenna.

T\R  |  W0      HB      BY      VK      ZS      PY       AVE.
W0   | 1000    930     980     770     820     750       875
HB   |  860   1000     910     770     640     650       805
BY   |  860    800    1000     600     620     760       773
VK   |  680    740     720    1000     880     960       830
ZS   |  590    590     660     820    1000     700       727
PY   |  490    410     360     510     790    1000       593

Distances to DX locations are important too but easily obtained
for comparisons, e.g., by using a program such as MINIPROP.


Bob, NM7M

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