[SADXA] 40m Daytime DXPropagation Corridor- Questions - Bill DavisW7EXG-

Tue Jan 22 00:47:14 EST 2019

Another Question that came up during this 40m Daytime DX presentation, as I
now recall, was regarding 30m propagation.  

What about 30m?

You may recall the foE data (converted to EMUF) was taken at the CACHOERIA
PAULISTA Ionic Sounding site in Brazil, when site was almost directly under
the sun [when sun was at -23.45 deg.].  The maximum EMUF was shown to be
about 7.9 MHz at Brazil's Solar Noon. This is worst case, but for Solar Low.

This suggests that 30m signals (f=10MHz) has the property that f > EMUF,
even at solar noon UNDER THE SUN.  This points out yet another significant
plus for Low Solar. At Low Solar (SSN=0), 30m is almost like 20m, in the
sense it is a daytime DX band. There is no daytime restricted region as far
as EMUF is concerned. However, 30m is affected more by D absorption then
20m, but since the absorption loss is related to [1/f^2], the 30m absorption
loss is about 50% less than for 40m. However, at LOW SOLAR, D-absorption is
about 44% that of HIGH SOLAR. So NOW IS GOOD for 30m daytime DX!! 

However, solar noon 30m DX may still be a challenge due to D-absorption, and
a 30m Solar Noon DX Award might also be a coveted prize. 

Next Year (likely Dec timeframe), someone in the SADXA needs to take the
coveted 40m DX Solar Noon Award (9900 miles) from W3LPL. I'll send the Dear
John Letter. 

I don't recall who asked about 30m, but I hope this answers their question. 

If other questions are out there, do not hesitate to ask. 

I am also looking into the question about foE contour offset provided by
www.solar.spacew.com. I am asking them for a physical explanation of this
offset, a question asked by one of our members. I believe this is a
graphical error, but we will see. It is in their best interest to respond,
since they are selling these types of product. 

73's
Bill W7EXG   

-----Original Message-----
From: sadxa-bounces at mailman.qth.net [mailto:sadxa-bounces at mailman.qth.net]
On Behalf Of W7EXG (Bill)
Sent: Friday, January 18, 2019 11:57 AM
To: 'Southern AZ DX Association E-Mail Reflector'
Subject: [SADXA] 40m Daytime DXPropagation Corridor- Questions - Bill
DavisW7EXG-

SADXA Members

Thanks to all who attended the 1-17-19 SADXA presentation on the 40m DX
Daytime Corridor. Please feel free to ask questions via the reflector or to
me off-line (W7EXG at Q.COM) regarding the presentation.

Here, I will try and address some of the questions or comments made during
the presentation. 

I believe a question was asked regarding Tucson to S. Atlantic paths at
Solar Noon by Jerry W6XI.  Jerry was correct; there is no 40m Daytime DX
propagation to the S. Atlantic region. I determined that after about 2100z
on Dec. 21st, the path is likely to open up.  This is because at Solar Noon,
these S. Atlantic paths must cross the "restricted" boundary (EMUF>7MHz and
High D absorption) preventing such propagation. I generated a graphic on
this particular path case and emailed to Jerry.

Jerry also asked about the Solar Noon DX Award Winning Path from W3LPL MD to
YC land. Why not more paths?  In thinking about this, W3LPL is a CW skimmer
station (or visa versa), and most likely just heard the YC station. I don't
know how the DX MAP web site works, but other YC or YBs may have been heard
but not reported in the timeframe window specified. I also know from my own
experience, that I have heard many LP 40m DX stations that I never saw on
the DC Maps to AZ? My only hope is the paths I did report on were valid, as
they supported the 40m DX Day propagation corridor concept.  I did all I
could to insure both calls were highlighted and valid at the ends of the DX
MAPS paths. 

The seasoned 40m DXers also confirmed that most of the post SR to pre SS
day-day 40m propagation was in fact LP, and not SP. I presented that I had
also personally confirmed LP for the DAY propagation to Asia / Indonesia day
areas 1.5 hours prior to AZ SS. I made the point that the Solar Noon
D-absorption between these two regions had constant lateral path
D-absorption, preventing the SP. 

It is true that the hop loss listed in presentation was for D-absorption
loss ONLY. This was in response to Wes's N7WS Question.  The ground Loss is
about 5.5 db/hop for 7 MHz @ 23 deg elevation angle and thus comparable to
the D-absorption loss - a correct observation by Wes. The sea surface loss
is only about 0.16 dB/Hop for same 40m condition. So, for 3 F2 hops over
ground to the terminator, a 16.5 db loss must be added. For 3 hops over sea
to the terminator, only about a 0.5dB loss is added. The ramifications of
this: - East cost to EU, or West Coast to Asia area and more has very small
sea loss to the respective terminators. However, the D-absorption loss will
dominate the loss over sea to the terminators as discussed. 

There may have been other technical questions I cannot recall to address
here, so please do not hesitate to ask again if questions were not addressed
to your satisfaction. 

If the SSN remains 0, (Low SFI), it is possible again to have another
opportunity next Dec. Solstice timeframe for some exciting 40m DX
propagation during the day, as discussed. But don't blink; it does not last
too long. 

73's
Bill W7EXG

-----Original Message-----
From: sadxa-bounces at mailman.qth.net [mailto:sadxa-bounces at mailman.qth.net]
On Behalf Of W7EXG (Bill)
Sent: Thursday, January 10, 2019 8:48 PM
To: 'Southern AZ DX Association E-Mail Reflector'
Subject: [SADXA] SADXA 1-17-19 Presentation - ABSTRACT-- 40m Daytime
DXPropagation Corridor- Bill Davis W7EXG-

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. 

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