[SADXA] Oct 20th SADXA Presentation Abstract - Gray-line / Terminator Enhanced Propagation - Bill Davis - W7EXG

[W7EXG (Bill)]

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 MEASUREED 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!)  

A summary is provided.