[SADXA] October SADXA meeting Thursday October 20th

[Larry Brown]

The October SADXA meeting will be held on Thursday October 20th
starting about 5 PM at Mimi’s Café, 120 S Wilmot.   Bill Davis,
W7EXG is scheduled to present the second part of his
Gray-Line/Terminator Enhanced Propagation: Lessons Learned
(Synopsis below).    See everyone Thursday.

 

73,

 

Larry Brown, W7LB

SADXA Secretary/Treasurer

 

 

PRESENTATION TITLE: Gray-line / Terminator Enhanced Propagation:
Lessons Learned from the Tucson / Heard-Island Experience -- PART
2 of 2

 

WHEN: Oct. 20th, 2016

WHERE: SADXA Meeting

DURATION: ~ 50min / 10 min Q&A

 

WHO: Bill Davis -- Licensed as W7EXG in 1956 Bill is an Electrical
Engineer, having retired from Motorola - after working 30 years,
as an Analog IC Design Engineer / Manager. Bill was a Senior
Member of the Motorola's Technical Staff, and a Dan Noble Fellow. 

 

ABSTRACT - PART 2

 

This Part 2 study was motivated by the observations of apparent
Gray-line signals between Tucson and the Heard-Island DXpedition,
by several SADXA members. 

 

Definitions for Gray-line and Terminator Enhanced Propagation will
be discussed.

 

Gray-line Propagation basics will show that Station Location
relative to Terminator is key, in defining Propagation Time in
terms of a Sunrise (SR) vs Sunset (SS) time differential. In
addition, the angular alignment of signal to the
Terminator/Gray-line is critical to enable real Gray-line
propagation. 

 

Gray-line Pre-Sunrise MUF Enhancement occurs due to F layer
ionization, approximately in the Civil Twilight region (~ 415 mi,
and ~24 min before sunrise). Data from Satellites, Dark North
Polar Regions, and Ionogram Soundings will provide clear evidence
of Pre-Sunrise F layer ionization.  

Ionogram data will also show, that Gray-line Pre-Sunrise Skip
Enhancements (or degradation) occur, due to F Layer Height
reduction beginning at the Nautical Twilight time, and continuing
well past Sunrise. 

 

A 4/6 UTC 40m Terminator Enhanced Propagation Corridor example
will be studied, using 4/6 North and Equatorial Ionogram sounding
data.  This data will show the 4/6 40m F region 10,200mi DAY
Propagation Corridor [between Tucson and Heard] is defined by slow
rising EMUF after Sunrise, [slow decaying EMUF prior to sunset
also occurs], enabling 40m F Region propagation during the DAY.  

 

The 40m F region DAY Propagation Corridor is then defined, in
terms of time and distance from the Terminators.  

 

F region Propagation Corridors will also be defined for 160m
through 30m bands, using archived Ionogram data for high and low
solar activity.  The F region Corridor limits for the 160m/80m
bands will also be shown to be at or near the terminators. The 40m
and 30m DAY and NIGHT F region Enhanced Corridors are also shown
relative to the Terminators. 

 

Bearing graphics [which are centered on Tucson], show that for
general 40m F Region Enhanced propagation, the bearings should be
no greater than +/- 38 degrees about the Terminator. Since the
terminator varies about +/- 32 degrees annually in Tucson, a 77%
annual world angular range is defined, as well as a 77% one day
world angular range for Dec 21st and June 21st. 

 

D absorption will be discussed, including excess D absorption
graphics that prohibited ANY Tucson-Heard propagation on 4/8 and
4/9.  

 

A 40m 4/6 MEASURED 13,868 mi Long Signal Path Loss is calculated,
based on measured received signal power in Tucson, System Gains,
and knowing Heard Transmitter Power.  

 

The 40m 4/6 THEORETICAL 13,868 mi Long Signal Path loss is also
calculated, based on losses due to the 18 hop F layer path,
Spatial Spreading loss, Ground and Sea reflections loss, and a
nominal D absorption loss as a function of distance from the
Sunrise terminator. 

 

A large discrepancy is shown between the Measured and Theoretical
Path Loss.

This strongly suggests that inter-layer [F/E and F/Es] and/or
Chordal hops were likely, even for a 40m Signal - IN APRIL. (not
reserved ONLY for summer 6m propagation!)  



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