This session was right down the line for July in terms of distances covered, S/N levels and activity. The reporting periods leading up to sunrise across North America saw a return of elevated K-indices up to storm levels. Solarham reports another geoeffective coronal hole rotating into view. Solar wind velocities have peaked so far above 600 km/s with averages near 590 km/s. The Bz is currently pointing slightly to the North but DST values have seen pronounced decreases.
Ken, K5DNL / WG2XXM, reported two WSPR stations and was decoded by sixteen unique stations, including 18 decodes from WH2XCR.
Phil, VE3CIQ, reported that he decoded three WSPR stations and was decoded by two unique stations, with the furthest signal 600 km away.
Neil, W0YSE/7 / WG2XSV, reports more of the same and offers these statistics:
The WG2XIQ grant was renewed, taking a month to complete. This is odd because my last renewal only took 3 business days. Nevertheless it is complete. But not for two more years. The expiration date was listed as a very mysterious December 30, 2017. Typically grants default to 24 months so why the change? This suggests that going forward OET will be moving Part-5 experimental stations out of the 472 – 479 kHz segment. What is still not known is how quickly Part-97 integration occurs. I would hope that we wont have to wait until January 1, 2018. Time will tell. I have notified a number of people “in the know” and begun asking questions to see what I can find out. Stay tuned.
Regional and continental WSPR breakdowns follow:
There were no reports from the trans-Atlantic, trans-African, or trans-Equitorial paths.
In the Caribbean, Eden, ZF1EJ, reported WG2XXM and WG2XIQ:
Laurence, KL7L / WE2XPQ, reports poor conditions with only WH2XCR making through the fog:
Merv, K9FD/KH6 / WH2XCR, experienced another typical July session. Consistency really is a good thing:
Jim, W5EST, presents “E AND F CRITICAL FREQUENCY GEOGRAPHIES. REAL HF IONOGRAMS.”:
“F-region critical freq fof2 geography worldwide is displayed at this fof2 web site: http://www.spacew.com/www/fof2.html . Recall from yesterday that the critical frequency is the highest frequency that an ionosonde can send straight up and still receive a reflection back from a given ionospheric region. Critical frequency fof2 corresponds to a highest electron concentration or density in the F2 region. For a MUF map, go to http://users.skynet.be/on5au/ , click on the Real-Time Prop-Maps button at left, and then click the button for MUF-F2.
Now, if 630m and 2200m reflect from the E-region, what about that critical frequency? For critical freq foe geography worldwide, see http://www.spacew.com/www/foe.html .
E-region daytime critical frequencies are generally lower than F-region critical frequencies. You can see nighttime E-region critical frequency as a big unmapped gray area on the global map. Its boundary is the lowest frequency available for mapping.
When the sun goes down, solar radiation no longer ionizes the ionosphere. Then, free electrons in each region recombine with ions at respective rates characteristic of each region.
Theory tells us that the electron concentration is proportional to the square of the critical frequency. Suppose the E-region critical frequency foe is 2 MHz in late afternoon. For foe to reach 630m, 475 KHz, in the evening means that the E-region electron concentration has to become over 17 times less for foe to reach 630m and about 210 times less for it to reach 2200m, 137.5 KHz.
The foe map suggests that the E-region critical frequency does fall dramatically fast during twilight. How far does it fall? The foe map goes down at least as far as 600 KHz at the end of evening twilight. Unfortunately for us, this leaves 475 KHz unclear, and begs the question regarding 2200m.
Even if the E-region critical freq foe falls below 475 KHz, foe applies to signals that are sent straight up—vertical incidence signals. We deal with oblique-incidence MF/LF signals that launch and arrive at much lower elevation angles, even close to the horizon. The highest frequency of oblique-incidence RF the E-region can reflect is therefore some multiple, roughly 3 times its critical frequency foe. Compared to electron concentration at 600KHz foe, the electron concentration would need to fall still further by factor of about 14 to release 630m low angle transmissions from E-reflections and give access to the longer distance opportunities of F-region propagation.
In short, the big unmapped gray area on the global map of nighttime E-region critical frequency foe leaves much unsaid that we MF/LF experimenters and hams care about! If the E-region is active for 630m receptions even in deep nighttime, I’d like to see a citation to the evidence. Could cosmic rays and incoming galactic radiation keep the E-region sufficiently ionized in deep nighttime for 630m reflection notwithstanding the absence of the sun’s radiation then?
Especially on the fall-winter transatlantic (TA) paths and the N.America-VK paths near the equatorial anomaly, does the E-region nevertheless have gaps or otherwise vanish sufficiently for our purposes to bring the longer-distance F-region into play on 630m? If you have clues to the answer, by all means e-mail us!
Now let’s turn to the subject of ionograms. Ionograms are graphs based on the time delay between the ionosonde acting like radar to send a signal frequency skyward and receiving a reflection back. The time delay is translated to height above the earth at which the reflection occurred. An ionogram is a graph of height versus frequency.
One would like to have a real-time ionogram for the ionosphere overhead especially any geographic location like a one-hop path midpoint where a sky reflection would be likely to occur. Failing that, it could be informative to study an ionogram for an ionosonde station somewhere in that geographic region at the same time UTC.
Introduce yourself to ionograms at https://www.ngdc.noaa.gov/stp/iono/ionogram.html .
See definitions of some ionogram abbreviations at http://giro.uml.edu/didbase/scaled.php .
From a top level ionosonde station list, drill down for ionograms by year, month, day. http://car.uml.edu/common/DIDBFastStationList . Day and night, ionograms are recorded from stations every 5 minutes. Try Millstone Hill (VT), Boulder (CO), Austin (TX), Eglin AFB (FL), Wallops Is. (VA), Idaho Natl. Lab, and Point Arguello (CA). Across the Atlantic, see Chilton (UK) and Dourbes (Belgium). Many other listed stations lack ionosonde curves for the different ionospheric regions.
Ordinary (O) wave reflections are rendered in red; and extraordinary (X) wave reflections show up in green. The subject of O/X waves calls for a blog post another day.
Secondary ionosonde reflections may also be seen at one or more multiples of a given ionospheric region height h. Real ionograms over 24 hours can interestingly depart from the summary information commentators give on web sites.
For VK ionograms, see http://www.sws.bom.gov.au/HF_Systems/1/3 .
If you have better ionogram web site links, especially ones that reach down to 630m and even 2200m, please share them with this blog. Thanks!”
Additions, corrections, clarifications, etc? Send me a message on the Contact page or directly to KB5NJD gmail dot (com)!