[SADXA] 40m Daytime DXPropagation Corridor- Questions - Bill Davis W7EXG-

[Wes Stewart]

Thanks again Bill for an interesting presentation.

My interest piqued, I was doing some Internet searching and came across this 
link: http://www.astrosurf.com/luxorion/qsl-hf-tutorial-nm7m.htm

Bob Brown was of course, the author of a couple of books of interest to DXers.  
1) "The Little Pistol's Guide to HF Propagation" and 2) "The Big Gun's Guide to 
Low-Band Propagation"

Each of these publications might be valuable additions to your reference libraries.

Wes  N7WS

On 1/18/2019 11:56 AM, W7EXG (Bill) wrote:
> 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.
>