On Tue, 11 Aug 1998 22:52:42 -0600 n4kg@juno.com (T A RUSSELL) writes:
>(It is my understanding from a highly qualified friend that different
>ASSUMPTIONS can lead to much higher wave angles using the
>same IONCAP program. I will ask for more details.)
Ioncap requires that you specify the entire transmitting and
receiving antenna system, and then it shows the parameters (snr,
takeoff angle, etc) for the strongest propagation mode for that
antenna system. If you specify low antennas, then the results may
very well favor the higher-angle modes, and vice-versa.
Ioncap also allows you to specify the minimum takeoff angle, in
addition to specifying the transmit and receive antennas. You
can use this to force the solution into higher angle modes. Here
is an example that I just ran. The transmit and receive antennas
were specified as isotropic, with 12 dB gain, sort of like a
small yagi on an optimum height tower, pointed at the target.
14 MHZ, February, SSN=105, 1700Z, Yuma, AZ to Brussels, Belgium
with minimum angle set at 0.1 degrees
results: takeoff angle = 2.5 degrees, receive snr = 40 dB
with minimum angle set at 2.6 degrees
takeoff angle = 7.2 degrees, snr = 33 dB
with minimum angle set at 7.3 degrees
takeoff angle = 11.2 degrees, snr = 25 dB
with minimum angle set at 11.3 degrees
takeoff angle = 15.23 degrees, snr = 17 dB
Notice that the 7.2 degree mode is only about 7 dB down from the
optimum mode. For a low antenna, this is probably the loudest
mode. This stuff is great fun to play with, and it's all free!
For a real hoot, you can approximate your antenna and local terrain
with YTAD, convert the YTAD results to a VOA antenna file with
MAKEVOA.EXE, then run VOAAREA, and make a color plot of
your snr contours over any geographic area, such as Europe.
Then you can do it all again, assuming you spend more money
on stacks and higher towers. Great stuff!
Dave Hachadorian, K6LL
San Diego, CA
K6LL@juno.com
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