[SADXA] SADXA 1-17-19 Presentation - ABSTRACT-- 40m Daytime DX Propagation Corridor- Bill Davis W7EXG-

[W7EXG (Bill)]

SADXA MEETING PRESENTATION 

DATE: 1/17/2019

TITLE: 40m Daytime DX Propagation Corridor

AUTHOR/PRESENTER: Bill Davis - W7EXG
SADXA Member, Motorola Retiree - EE
Licensed: 1956 (62 years)

ABSTRACT

A 40m Daytime DX Propagation Corridor will be defined as a 40m DX day region
adjacent to the terminator, having a width W defined between the terminator
and an EMUF=7MHz boundary. 

This results, since the E layer electron density decreases between the
EMUF=7 MHz boundary and the terminator. This allows the 7 MHz signals to
penetrate the E layer and propagate via the F2 layer in this day DX corridor
region. 

The basics of the E layer are presented, including the critical E frequency
[foE](E layer Plasma Frequency), and the M factor associated with the
Angular Penetration of the E Layer. EMUF will be defined, and EMUF equation
developed for typical 40m 23 deg elevation. 

The world wide foE data is presented as a function of Solar Zenith and
latitude. Specific EMUF data vs Time is presented from the Austin (30 deg
Lat) and a South American (-22.7 deg) RF Ionogram sounding Sites, taken
during the December Solstice. 

The seasonal variation of the terminator [and 40m Day DX Corridor] is also
shown, including the December Solstice when the Solar Noon northern
terminator boundary is only ~1100 mi from the northern US border.  This is
the ONLY seasonal time, when almost the entire US is in the 40m DX Corridor
during the day, including Solar Noon. This 40m Day DX condition is best,
when ionization of the E and D layers is minimal, such as during LOW SOLAR
radiation (like NOW!). 

D-absorption is also graphically shown as a function of the Solar Zenith and
Sun Spot Numbers (SSN), including the D absorption expected within the 40m
Day DX Corridor. 

Finally, 40m DAY DX propagation corridor examples are presented from Screen
Captures of the actual 40m DX paths from DXMAPS site. The included 40m
examples are: Day-Day, Day-Night, Day Western States, Day Eastern States,
Observable D absorption effects, Near SS Long Path propagation, impossible
paths with bogus call signs, and Solar Noon 40m DX propagation.