1. Introduction
The author established an amateur radio station with the callsign BG5CZD in early March of this year, and has been actively pursuing VHF DX since then, achieving some results. This article is based on a recording made by the author between 12:47-12:58 on April 29, 2024.(BJT)Using a 4-element Yagi antenna (2.4m (0.4λ) main boom, height approximately 0.5-0.7λ, free space gain of 8.54 dBi, F/B = 18.83 dB) at my QTH (PM00be), and receiving and processing a signal transmitted in FT8 mode using a Yaesu FT-710, which was then decoded, encoded, and retransmitted:
20240429_044745.113(0) Transmitting on 50.313 MHz + 1120 Hz using FT8: CQ BG5CZD PM00
20240429_044815.074(0) Transmitting on 50.313 MHz + 1120 Hz using FT8: CQ BG5CZD PM00
20240429_044845.071(0) Transmitting on 50.313 MHz + 1120 Hz using FT8: CQ BG5CZD PM00
20240429_044915.076(0) Transmitting on 50.313 MHz + 1120 Hz using FT8: CQ BG5CZD PM00
20240429_044945.085(0) Transmitting on 50.313 MHz + 1120 Hz using FT8: CQ BG5CZD PM00
20240429_045015.054(0) Transmitting on 50.313 MHz + 1120 Hz using FT8: CQ BG5CZD PM00
20240429_045045.177(0) Transmitting on 50.313 MHz + 1120 Hz using FT8: CQ BG5CZD PM00
20240429_045115.145(0) Transmitting on 50.313 MHz + 1120 Hz using FT8: CQ BG5CZD PM00
20240429_045145.090(0) Transmitting on 50.313 MHz + 1120 Hz using FT8: CQ BG5CZD PM00
20240429_045200 -12 0.6 1240 ~ JD1BQP IW9HII JM67
20240429_045215.093(0) Transmitting on 50.313 MHz + 1120 Hz using FT8: CQ BG5CZD PM00
20240429_045215.752(0) Rebroadcasting 50.313 MHz +1120 Hz FT8: IW9HII, BG5CZD, PM00
20240429_045230 -12 0.5 1240 ~ JD1BQP IW9HII JM67
20240429_045245.087(0) Transmitting on 50.313 MHz + 1120 Hz using FT8: IW9HII, BG5CZD, PM00
20240429_045300 -8 0.4 1241 ~ JD1BQP IW9HII JM67
20240429_045300 -12 -0.0 1735 ~ BG5GNC BD7TBP OL42
20240429_045315.084(0) Transmitting on 50.313 MHz + 1120 Hz using FT8: IW9HII, BG5CZD, PM00
20240429_045345.096(0) Transmitting on 50.313 MHz + 1120 Hz using FT8: IW9HII, BG5CZD, PM00
20240429_045415.057(0) Transmitting on 50.313 MHz + 1120 Hz using FT8: IW9HII, BG5CZD, PM00
20240429_045445.159(0) Transmitting on 50.313 MHz + 1120 Hz using FT8: IW9HII, BG5CZD, PM00
20240429_045515.088(0) Transmitting on 50.313 MHz + 1120 Hz using FT8: IW9HII, BG5CZD, PM00
20240429_045545.143(0) Transmitting on 50.313 MHz + 1120 Hz using FT8: IW9HII, BG5CZD, PM00
20240429_045615.135(0) Transmitting on 50.313 MHz + 1120 Hz using FT8: IW9HII, BG5CZD, PM00
20240429\_045630 -18 0.1 1282 ~ BG5GNC BG7IKK OL63
20240429_045645.112(0) Transmitting on 50.313 MHz + 1120 Hz using FT8: IW9HII, BG5CZD, PM00
20240429_045715.088(0) Transmitting on 50.313 MHz + 1120 Hz using FT8: IW9HII, BG5CZD, PM00
20240429_045745.122(0) Transmitting on 50.313 MHz + 1120 Hz using FT8: IW9HII, BG5CZD, PM00
20240429_045815.082(0) Transmitting on 50.313 MHz + 1120 Hz using FT8: IW9HII, BG5CZD, PM00
Additional conditions: weather (temperature, etc.) for the current day and the previous three days.
2024-04-28 Sunday 24°C19℃ DarknessLight rain Northwest wind, level 1
2024-04-29 Monday 26°C13℃ FogLight rain Northeast wind, level 2
2024-04-30 Tuesday 17°C13℃ LargeLight rain Northeast wind, level 3
Since then, I have not received any further strong signals from Europe, and I haven't received any signals from Europe at all. This has naturally prompted me to think: why did I suddenly receive this signal (presumably JD1-IT9) at that time?&(IT9-BY5's independent unidirectional propagation), until I came across the article "SSSP: Short Path Summer Solstice Propagation" written by Japanese amateur radio operator Han Higasa JE1BMJ, which was translated into Chinese by our teacher Zhang Liyong (BG3MNR). This made me consider whether it might be a similar sudden short-path propagation, similar to SSSP.
2. Casual conversation
2.1 Definition of SSSP
SSSP describes short-path propagation in the Northern Hemisphere before and after the summer solstice, and similar propagation in the Southern Hemisphere before and after the winter solstice (taken from the article by Han Higasa JE1BMJ in Japan, translated by Zhang Li Yong BG3MNR as "SSSP: Short-Path Summer Solstice Propagation," which is no longer cited; subsequent references will be presented with annotations). 2.2. Assumptions about propagation paths using SSSP
Figure 1
Figure 1 shows a general model for sporadic E-layer propagation. In this general model, 50 MHz signals are refracted by the E-layer ionosphere between the transmitter and receiver, reflecting or bouncing back several times from the Earth's surface, typically referred to as sporadic E-layer single or double jumps. However, when discussing summer short-path propagation between East Asia and Europe, some question the credibility of this assumed propagation model.
Assuming the height of the E-layer is between 90 and 100 km, the maximum distance for a single hop would be approximately 2000 km. However, the propagation path length from East Asia to Europe ranges from 9000 to 12000 km. Therefore, in classic, multi-hop sporadic E-layer propagation, the number of hops required is typically five, six, or even seven or more.
Along the E-AS to NA propagation path, a large area is ocean. However, along the E-AS to EU path, there is almost no large water surface (only the Mediterranean Sea, Black Sea, and Caspian Sea, but once these waters enter Asia, they disappear), so most of the 50 MHz signals will be scattered and/or absorbed by the ground with low reflection efficiency, leaving only a small portion that can return to the E-layer electron cloud.
In the reception on April 29th, the signal from IW9HII was extremely strong and virtually distortion-free, also stable and without any jitter. It closely resembled a signal originating from within visual range or at a distance of one or two hops. This means that these signals did not exhibit the distortions (such as those caused by multiple reflections off the Earth's surface, like EME) that were expected due to their propagation paths being significantly longer. Alternatively, we can assume that the propagation path is very short.
Therefore, when considering a specific article, could this also be considered a short-path propagation of the SSSP type, with the propagation path resembling the "terminal-to-terminal" form shown in Figure 2?
Furthermore, based on data from the Space Environment Research Forecasting Room of the National Space Science Center of the Chinese Academy of Sciences (as shown in Figure 3), I suspect that a strong geomagnetic disturbance caused the formation of a small PSME region in mid-to-high latitudes, and this occurred near BY5.&There were also two recently controlled points in the airspace above JD1/o.
The problem arises: why do the JD1/o and BY5 radios independently exhibit the situations where JD1/o is visible on IT9, but IT9 is not visible on JD1/o; and where BY5 is visible on IT9, but IT9 is not visible on BY5? The author believes
Figure 2
Figure 3 (Data from SEPC of NSSC)
Given that the solar activity level for this event was only M1.6, the resulting PSME region was not very large and did not persist for long; furthermore, the propagation conditions were quite demanding. Additionally, the recent control points were also short-lived and their locations and propagation conditions were equally challenging. As a result, any station within a 300km radius centered on my PM00be grid would receive this signal, such as BG7XWF.&BG5BAA&The pioneers, such as BA5CW, who used Yagi antennas with a main element length of 1λ or more and a height approximately equal to 1λ, and consisting of 5-6 elements, did not receive this signal either. This indicates the strictness and demanding nature of the recently implemented control point, which resulted in the unidirectional propagation path described above.
2.3. Plan
As for the plan, in the foreseeable future, I intend to accelerate the construction of my VHF DX base, learn from experienced operators, and extensively study technical books such as "Antenna Handbook" and "Amateur Radio Handbook," as well as practice building Yagi antennas, amplifiers, and learning circuit design. I also plan to explore SSSP propagation and continue enjoying the fun of DXing.
3. Conclusion
My knowledge and experience in the 6-meter band are limited, and I can only be considered a "beginner" in DX. This article is simply my personal exploration for entertainment purposes, based solely on my own understanding ("I vaguely understood"). I would like to express my sincere gratitude to all the senior members who have supported me along the way. I also hope that I will eventually be able to successfully communicate with European radio stations. As Ham Higasa JE1BMJ wrote in the original article: there are still many unsolved or unknown phenomena related to SSSP propagation, and I hope that more enthusiasts of the 50 MHz band will continue to observe, research, and explore SSSP.
4. References
4.1. "Radio Wave Propagation Handbook", by Sakuichiro Wada, CQ Pubs, Japan
4.2. "Polar Mesosphere Summer Echo" (PMSE)"Review of observations and current understanding" by M. Rapp and E.J. Lubken, 2004
4.3. "Radio Auroras", by Charlie Newton, G2FKZ, RSGB
4.4. The ARRL Handbook for Radio Amateurs, 1993, ARRL
4. 5. "SSSP: a newly discovered propagation on 50 MHz", by Han Higasa, JE1BMJ, CQ Ham Radio, September 2006, CQ pubs, Japan.
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