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[TowerTalk] Arrival Angles

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Subject: [TowerTalk] Arrival Angles
From: (Andy Cook G4PIQ)
Date: Mon, 15 Dec 1997 19:45:05 +0000
We've seen quite a lot of talk on and off about what is the optimum
height for an antenna of type x to be mounted at, and the answer, quite
rightly, comes back that there is no substitute for having a variety of
heights available.

It's seems likely that arrival angles are not static over even short
periods of time - listening to a signal with QSB on a low and a high
antenna often shows the QSB to be out of phase between the two.

All the basic propagation prediction software I have seen shows a single
arrival angle for a particular propagation mode, route, solar
conditions, month etc. I suspect what we see in reality are signals
arriving at a variety of angles. Has anyone here any good suggestions as
to where I can find some software which gives an idea of the
distribution of angles which we are likely to see over a particular

I've had a look at VOACAP and didn't find what I was looking for, but I
may just have been being a bit dumb. 

On a similar topic, the folklore of the low bands is that there are
often nights when the verticals are good and nights when the horizontal
antennas are good. I've always put this down to differing arrival angles
between those nights rather than anything fundamental about the arrival
polarization. Anyone care to comment?


Andy Cook, G4PIQ

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