Of course there is no contribution from the daylight side - that goes
without saying.
However, I would say 100% of topbanders would call their
other-side-of-the-world receptions "antipodal" and 100% know that there is
no signal via the daylight side of earth.
Now that we've gotten past the word nitpicking, what's the evidence to
discard antipodal focusing? What's the explanation for the greater signal
strengths of antipodal stations than very far away but not antipodal
stations? Is there DF data from anyone that says the incoming signal is from
a narrow range of angles?
Chuck
-----Original Message-----
From: topband-bounces@contesting.com [mailto:topband-bounces@contesting.com]
On Behalf Of Thomas Giella KN4LF
Sent: Monday, March 29, 2004 4:06 PM
To: a Topband eList
Subject: Topband: MF Anti-Podal Propagation Enhancement
Chuck Hutton Said:
I - and a lot of DX'ers who specialize in international MW DX - would
disagree with this. There are many examples of incredible antipodal
receptions, with recent examples being the 300 kw 1557 Taiwan station
received with some regularity in Brazil.
Thomas Giella KN4LF Says:
I've been a medium frequency AM broadcast band DXer since 1965. True
unskewed antipodal propagation enhancement can only occur at frequencies
that can propagate in daylight. At any given moment many of the propagation
paths that are involved in antipodal propagation enhancement at medium
frequencies are shut down by daylight D layer absorption, period!
Most of the propagation enhancement that we may mistake for antipodal
focusing is actually via the E Valley/F Layer ducting mechanism.
73 & GUD DX,
Thomas F. Giella, KN4LF
Retired Space & Atmospheric Weather Forecaster
Plant City, FL, USA
Grid Square EL87WX
SKYWARN Observer # HIL-249
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