locked Re: Meteor Scatter
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I've had excellent results with 6 meter antennas at a height of
50 feet (80 meters). That puts the 3 dB points of main lobe at
3 and 8 degrees corresponding to a single-hop sporadic-E range
of 1300-1900 km (800-1200 miles). Its first null is at 11 degrees
degrees corresponding to a relatively unimportant very close-in
single hop sporadic-E range of 1000 km (600 miles).
Doubling antenna height to 100 feet improves antenna gain by
6 dB at only single hop sporadic-E distances beyond 2000 km
(1250 miles) and double hop distances beyond 4000 km (2500 miles)
but at the very significant cost of placing a very deep null at 4 to 6
degrees, a very important range of angles for sporadic-E propagation.
Tilting a single Yagi by 20 degrees reduces its gain by about 3 dB
and very significantly broadens the 3 dB beamwidth of its elevation
pattern by almost completely filling in its first null. This isn't very
useful for sporadic-E propagation except at a relatively unimportant
very close-in single hop sporadic-E range closer than 1000 km
From: "Palle Preben-Hansen, OZ1RH" <palle@...>
Sent: Wednesday, April 22, 2020 6:42:21 PM
Subject: Re: [WSJTX] Meteor Scatter
What is the point in tilting the antenna 15 deg up? Almost all MS QSO's requires a radiation angle less than 10 deg. Also tilting a beam does not change its radiation anglemuch as the radiation angle is determined by the antenna height above ground, see www.oz1rh.com with www.qsl.net/oz1rh/gnd_gain_eme_2002.zip
Radiation angles needed.
Supposing the MS reflections takes place at 110 km of height the needed radiation angle can be taken from this diagram:
As you can see angles below 10 degrees will fit a QSO distance over 1.100 km. The height of your antenna should reflect this. If you are on a hilltop or have a tall tower you could end up with too low angle of radiation for a 700-1.100 km QSO. However the meteors are random and not all are burning at exactly 110 km, so do not take this curve too seriously, but try MS out and see how you do.
73, Palle, OZ1RH