Hi Jim --
Are you familiar with the database that Dean Straw N6BV has compiled in the
"ARRL Antenna Book"?
Dean's database is far better for your purpose because is does NOT impose a
radiation pattern on the endpoints of the path; i.e.,
isotropic radiators are assumed. That means the data indicates what paths are
possible. Knowing this information one can proceed
to design a set of antennas which cover all the necessary takeoff angles and
Note that Dean's data is for an undisturbed ionosphere.
Now, your stated goal is to decide which band to use at a specific time
during a contest. ANY ionospheric model will only give
you an approximate idea of what bands and paths might be open. All these
models generate results which are rough probabilities.
But in a contest there are three confounding factors:
1) Today's ionospheric conditions may not resemble the smoothed conditions
assumed by the models.
2) More importantly, small scale ionospheric variations mean that a path
may open slightly early, close slightly later, or wink
open and closed. These variations could be 30 minutes to several hours -- and
the successful contester will want to be there to
take advantage of (or compensate for) these variations.
3) It doesn't matter if the path is open, when there are no stations to
work. There are many times in contests where paths are
wide open (e.g., from the Pacific to the USA) but relatively few contest QSOs
are being made. Sometimes the stations at one end of
the path are busy with a different opening.
Dean's database gives you all that you will need to form a rough band
operating plan with which to tackle a new contest.
But during the contest, the quickest way to calculate what band is effective
for critical contest QSOs is as follows: Switch to
the band in question, point your antenna, and listen. If nothing heard, call
CQ a few times. The ionosphere will make all the
necessary calculations and give you a result: you will work someone, or you
won't. The ionosphere's calculator takes much less work
to use ... and it's more fun, too!
Save all your database manipulation time for antenna construction.
-- Eric K3NA