[SADXA] 40m Daytime DXPropagation Corridor- Questions -BillDavisW7EXG-
W7EXG (Bill)
W7EXG at q.com
Wed Jan 23 13:20:46 EST 2019
Hi Dave,
This is a great question: Can the 40m DX DAYTIME Corridor be related to
higher frequencies, such as 30m?
Actually the correct answer for 30m is as follows:
A) NO! RIGHT NOW, there is NO LIMIT to the 30m DAYTIME DX (F2 Layer)
propagation for the current LOW SOLAR conditions. 30m F2 Layer DX is
worldwide during the day.
B) YES!! In about 6 years from now (+/-) -- YES, there will be a LIMIT to
the 30m DAY DX (F2 Layer). Thus 30m F2 Layer DX will NOT be worldwide, and
a 30m F2 Layer DX DAY corridor will result for HIGH SOLAR, just as there IS
a 40m F2 Layer DX for HIGH OR LOW SOLAR. So it depends on the HIGH or LOW
Solar State when you ask!!
THE NO
To elaborate, we are currently in the Low Solar (SSN=0) state. The
CACHOERIA PAULISTA, Brazil peak EMUF Solar Noon data (under the sun) is much
less than f =10 MHz. The 30m f > EMUF, and thus the E layer is not a
limiting factor in 30m DAYTIME F2 Layer DX anywhere in the world. The 30m
signal will pass though the E layer and access the F2 layer worldwide. Thus
for this case, there is no 30m Propagation Corridor, since 30m DAYTIME F2
Layer DX is possible, and unlimited (by E-Layer) worldwide.
THE YES
However, during HIGH SOLAR, when foE (and EMUF) is 40% higher then the
current LOW SOLAR (pointed out in presentation), the EMUF will exceed about
11 MHz. Thus, for f = 10 MHz, f < EMUF and there will be places in the world
(near solar noon Z=0) where the E layer is a limiting factor for 30m DAYTIME
F2 layer DX. Within these regions, 30m hops will be reflecting OFF the E
layer, and not the F2 layer. Thus during HIGH SOLAR conditions, there will
be a 30m DX DAY F2 Layer Propagation Corridor, as similarly described for
40m.
HOW ABOUT A NIGHT COMMENT
During the night, the MUF of the F layer becomes the limiting factor, for
20m, 30m and sometimes even 40m. The MUF equation is similar to that derived
for EMUF in the presentation.
In general, MUF(F2) = M x foF2, where:
MUF(F2) is the MUF for the F2 layer.
M is the angular elevation dependent M Factor
foF2 is the Critical Frequency of F2.
For a 30m Vertical, or a Dipole/Yagi antenna at 60 feet (0.61 wavelength),
the elevation angle is about 22 deg. For this case, M = 2.1 for 22 deg
elevation for 350 km of F2 Height.
Thus the equation -- MUF (F2) = 2.1 foF2 is used.
Since it is desired that MUF (F2) > 10 MHz for 22 degree 30m propagation,
fof2 > 4.78 MHz for 30m DX propagation using the F2 layer.
In looking at the current foF2 maps per the link below
http://www.spacew.com/www/fof2.html
It should be clear from these foF2 maps that during the night near Tucson's
32 deg latitude, Critical frequency foF2 > 5 MHz at SS, but continues to
decrease through the early evening and become < 4.78 especially towards the
latter part of the night, and early AM [before Sunrise]. foF2 then rapidly
rises during the SR Grayline and into the DAY region.
Based on this foF2 map nighttime data, I would expect 30m F2 layer DX (22
deg elevation) is possible in Tucson during the early evening on 30m, but
dwindles with time into late night / early AM. As the grayline approaches
near SR, the 30m F2 Layer DX would pick up again and into the DAY.
I checked Austin's (30 deg lat) foF2 data from SS to SR, and it more of less
agrees with the foF2 map data at 30 deg.
I have not been on 30m at night for a long time, so I hope all this makes
sense to those who are currently monitoring 30m at night.
20M VS 30M VS 40M
You were also thinking that 30m was more like 40m then 20m. Here are my
thoughts on this comparison question.
20m vs 30m
During the day,
20m has less D absorption loss than for 30m
During LOW SOALR, both 20m and 30m can access the F2 layer
worldwide.
During High Solar, 20m can access the F2 Layer worldwide, but the
EMUF can increase > 10 MHz, and prevent some of the world regions from
allowing F2 layer propagation for 30m. This will form a 30m DX DAY
propagation corridor as discussed for 40m.
During the night
During High Solar when MUF(F2) > 14 MHz, both 20m and 30m will
experience world wide DX in the F2 layer.
During Low Solar when 10MHz < MUF(F2) < 14 MHz, 20m will be dead,
while 30m can still experience DX in the F2 layer - as discussed above. This
is happening now.
40m vs 30m
During the day,
30m has less D absorption loss than for 40m
During LOW SOALR, 30m can access the F2 layer during the DAY
worldwide, while 40m DAY DX path is limited to the 40m DX DAY Corridor as
discussed in presentation.
During High Solar, the EMUF can exceed 10 MHz in DAY world regions.
Thus BOTH 30m and 40m cannot access the F2 layer except for 30m and 40 meter
DAY DX corridors as describe for 40m.
During the night
During High Solar when MUF(F2) > 10 MHz, both 40m and 30m will
experience world wide DX in the F2 layer at night.
During Low Solar when 7MHz < MUF(F2) < 10 MHz, 30m will be dead,
while 40m can still experience DX in the F2 layer - as discussed above.
NOTE: Right now, MUF(F2) is varying during the night, and highest (> 10 MHz)
right after SS, but dwindles < 10 MHz as the night progresses.
During Low Solar when MUF(F2) < 7 MHz, 40m and 30m will BOTH be
dead.
NOTE: Since MUF(F2) = 2.1 foF2, wherever one observes foF2 < 3.3 MHz, 40m
will ALSO be dead for 22 deg 40m elevation angles. It is common for this
condition to occur during a low solar night. Hams who have experienced many
solar cycles know the feeling of a dead 40m at night during low solar. It is
somewhat difficult to believe when it occurs, or is observed.
I know this is a lot of material to digest in my attempt to answer this
question. There really is not a simple answer, unfortunately, due to
complexities of varying solar conditions.
Thanks for your question Dave,
73's
Bill W7EXG
-----Original Message-----
From: sadxa-bounces at mailman.qth.net [mailto:sadxa-bounces at mailman.qth.net]
On Behalf Of w7aqk
Sent: Tuesday, January 22, 2019 8:58 AM
To: 'Southern AZ DX Association E-Mail Reflector'
Subject: Re: [SADXA] 40m Daytime DXPropagation Corridor- Questions
-BillDavisW7EXG-
Bill and All,
I think that was me asking about 30 meters. My purpose was to learn if you
thought any of your findings could be extrapolated to 30 meters. Said
differently, just how specific is your info with regard to frequency. To
me, and this is probably more intuitive than anything, I find 30 meters to
be more like 40 meters than it is like 20 meters insofar as it seems to be a
"24 hour band". Still, being somewhat higher in frequency, I think it might
have better daytime DX possibilities, but I can't say how much. Your
answer suggests that may not necessarily be the case. 30 meters is very
under-utilized, and so I find it hard to get a really good feel for "what's
possible" on that band. In other words, very often propagation there is
good, but nobody is using the band! Lately I've occasionally been doing
very rudimentary testing just by seeing which RBN's I can bring up. These
days, being at such a poor part of the solar cycle, it's hard to draw any
meaningful conclusions using my rudimentary methodology! Hi.
Anyway, I appreciate your follow-up info. Thanks for taking time to do
that.
Dave W7AQK
-----Original Message-----
From: W7EXG (Bill)
Sent: Monday, January 21, 2019 10:47 PM
To: 'Southern AZ DX Association E-Mail Reflector'
Subject: Re: [SADXA] 40m Daytime DXPropagation Corridor- Questions -
BillDavisW7EXG-
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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