Ionospheric Highways

Ionospheric Highways
One lane or two

Having spent >60 years as a relatively ignorant HF user of the Ionosphere I recently decided it was time for self-improvement. My re-education began stimulated by reading some old publications of the NorCal QRP Club (long may it survive and prosper). The article that captured my attention was included in the October 17 1998 Pacificon proceedings; entitled QRP DX’ing and Propagation Predictions by Ade Weiss W0RSP . The Pedersen mode of propagation was particularly interesting as it was described as being asymmetrical. Asymmetrical/non-reciprocal incidents have been reported for many decades and it seemed appropriate to make these my focus.

The first question to be answered is; do non-reciprocal paths actually exist? If yes obviously the followup questions would be What When and How. I decided to begin with information published in professional and research circles. A book entitled “Ionospheric Radio Communications” has remained neglected on my shelf for many years so was clearlly a place to start. The book is a collection of papers published in the proceedings of a NATO Institute conference in 1967, it was principally concerned with communications in the Arctic (no prizes for understanding why). Four papers on LF and VLF communications were included which are of topical interest due to anticipated Amateur allocations.

Nine papers and a summary of discussions on HF were included. One paper had a section on levels of signals travelling in opposite directions. Now when this subject comes up the common reaction is the ionosphere behaves as a true reflector where anglesof incidence and relection are equal, and thus communications between two points would be reciprocal. However the paper contained the conclusion that “Most ionospheric paths are non-reciprocal” due only to interactions with the earth’s magnetic field. I wondered if communications at high lattitudes might be a special case. It is hard to dig deeper into this subject and proving or disproving this mode behavior becomes a real challenge.

After some rather tedious reading I realized that the subject involved many dimensions includng the sun, ray angles, polarization, frequencies, velocity, orientation of the magnetic field, ionosphere density etc. It became clear that relevant computer software would be essential therefor time to seek guidance from some subject matter experts such is Carl Leutzelschwab K9LA. Carl is a true expert and prolific educator. He has studied the subject of asymmetry and propagation in general for several years and is willing to share his findings- including a presentation via Skype at a future Club meeting.

Carl’s site is a treasure trove of information on propagation,his monthly featured articles are consise and most informative. The topic for Feb 15 2015 was enttiled “One-way propagation” which reported on the investigation of a specific example however no asymmetry was found.

The May 2017 feature is entitled 3DThinking. The terms Ordinary and Extraordinary Waves were included which are believed to have a direct bearing on asymmetry. A reported path between Thailand and Germany was investigated. The incredible computational power of Proplab Pro V3 was frankly an eye-opener. However the investigation concluded that skewing of the waves did not cause assymetry and that “The fat lady has yet to sing”.

I strongly believe that Carl and a few other talented individuals will not let this rest as incidents keep showing up.

Ron W6WO June 9 2017