Last Updated on August 22, 2023 by John Berry
Research aim: “to define a universal master algorithm for prediction of signals of interest to the radio amateur“
There is much known about radio wave propagation. There’s a whole ITU ‘sector’ dedicated to ‘radiocommunications’ and much of that is directly or indirectly associated with propagation. And there’s a huge body of knowledge set out in various papers and books by authors like Les Barclay, G3HTF (SK).
But the ITU and those authors have generally focussed on signal receipt for large percentages of time. For them, the signals received for small percentages of time are typically a nuisance – interference that would degrade otherwise healthy communications in the Mobile, Fixed, Broadcast and Satellite Services.
For radio hams (in the Amateur Service), it’s that low chance of receipt that makes the propagation mode worth chasing. Something that’s only there for something like 0.1% of time or less is DX indeed.
My interest is in propagation that supports communications for small percentages of time.
Signals for high percentages of time (and to a lesser extent signals that would be interferers for small percentages) are described by algorithms and implemented as computer code in radio planning and modelling tools. A good example of a paper is Recommendation ITU-R Rec. P.526 Propagation By Diffraction, currently on its 14th edition. Any engineer wanting to model propagation in the troposphere over obstructed paths will most likely use the algorithms cited there.
About algorithms
Recommendation ITU-R P.526 is just one of many publications containing algorithms. If, for example, one station is ‘in the clutter’, moving through a town, a different algorithm would be used to describe propagation in this multi-path environment. This second algorithm would modify the first. And a third algorithm would be needed to describe how the received signal would likely vary in the long term.
Ultimately, a clutch of algorithms is needed to best model the path and resulting received signal and those vary depending on the path geometry, propagation mode and technology. This algorithm amalgamation is the classic approach used in propagation modelling tools.
Having developed pseudocode in HTZ Warfare and ICS Telecom, I’m most familiar with those tools from ATDI, but there are many. There are several in the amateur domain based on the professional tools and algorithms such as Radio Mobile by Roger Coudé, VE2DBE.
So, propagation modelling – and hence propagation prediction – requires a clutch of algorithms.
The professional tools use a decision map to determine which algorithms to use. Here’s an example taken from Rec. ITU-R P526-10.
The algorithms are annotated by the paragraph character (§). Each END mark shows the recommended algorithm. If the path suggests diffraction over the horizon, §3.1 should be applied with its ten pages of formulae and nomographs. The §3.1 algorithms would then be added to those from other publications such as Recommendation ITU-R P.525-3 Calculation of Free-Space Attenuation to define path loss due to free-space plus diffraction – and so on. Every technology and propagation mode can be modelled using this approach. Each algorithm is what I term on this website a propagation primitive.
But there are no such primitives targeting amateur radio.
Decision maps and primitives
There’s plenty myth about things like sporadic E propagation and propagation via the auroral oval. And there’s F-region propagation using Recommendation ITU-R P.533-9 (with parallels in VOACAP and others). But there’s no definitive decision map for signals received for low percentages of time.
My aim is to define a universal master algorithm for prediction of signals of interest to the radio amateur. It’s a long project that started in 2021! The target completion is 2026.
And my focus is the use of academic and other validated publications.