That depends upon a large number of factors. VOAAREA, one of the
applications packaged with VOACAP, will give you a nice pretty area map
showing the bounces in all directions and their effect on signal
strength for any set of parameters (time of year, time of day, solar
flux level, frequency, etc). You can even generate your own antenna
file (essentially the antenna pattern) to tailor it to your own situation.
All of that is simply prediction, of course, but it's based upon a
generally accepted computer model and a lot of historical data.
VOACAP/VOAAREA probably has the most versatility for evaluating various
input conditions and displaying the results in various ways, but the
user interface is unquestionably one of the clumsiest ever devised by
man. HAMCAP, which is actually just a better user interface for the
VOACAP engine, is slightly more limited in options but is MUCH more
straightforward to use. Both programs are free. I tend to use VOACAP
to display path loss rather than signal strength or S/N ratio. Path
loss pretty much eliminates considerations of power level and local
noise levels and therefore gives me a cleaner picture of raw
propagation. YMMV.
By the way, VOACAP also has the ability to display preferred takeoff
angle as the output parameter, although even the author of the program
states that takeoff angle is probably the least reliable in terms of
supporting background data of all 20 parameters that VOACAP can
display. Still, it is rather amazing to see just how low an angle is
optimum for most paths, including some that we would normally consider
to prefer a higher angle.
73,
Dave AB7E
On 4/25/2011 6:59 AM, k2drn.cw@verizon.net wrote:
> has anyone ever seen statistics on how many times a given signal bounces from
> earth to ionosphere as it travels around the earth and what amount of loss is
> involved each time it bounces? David K2DRN
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