Topband: Topband Takeoff Angles

[John Kaufmann]

On Wed, 06 March 2002, "KN4LF, Thomas Giella" wrote:

Uncle Sam research says it's necessary to focus
> the majority (so to speak) of the RF under 30 deg. with 18-22 deg. being
> optimum to enter the E valley-F layer duct or for chordal hop propagation
> past approximately 3100 miles. Of course though as the ionosphere changes
> density and height continuously it's a "highly" variable thing.
> 



I have a lot of experience with angle-of-arrival observations on 80m, which might (or might not) be relevant to 160m.  It's based on the stacked 80m antennas on a 300 foot tower at KC1XX (www.kc1xx.com) which can be phased for low-angle or high-angle operation.  By comparing signal strengths in the two modes, it's possible to get some estimates of arrival angle.  

Into Europe we see a huge amount of variability in arrival angles, from hour to hour and from day to day.  There does not seem to be much predictability to it.  Really low angles (15 degrees or less) are fairly rare and when they do occur, it's when the band first opens (before local sunset) or when it closes (after European sunrise).  Angles as high as roughly 35-45 degrees also occur from time to time, mainly before local sunset or during geomagnetic disturbances.  I would say the "average" angle of arrival is around 25 degrees for Western Europe to W1 and somewhat lower for Eastern Europe.  It also gets quite low into central Asia and the Pacific.  I would expect the angles to Europe to be lower for people who are farther away from Europe than W1.

I wish we could construct a similar stacked antenna for Top Band so I could give you direct data for 160. :-)

73, John W1FV