Last Updated on October 12, 2025 by John Berry
Past talk – Aircraft scatter explained – see below for video
Friday 10th October 2025, MSARS and online. One of several GM8JBJ ham radio events.
To exploit aircraft scatter for VHF/UHF/SHF communication it’s essential that radio amateurs understand the mechanism. I started this presentation with a demonstration of aircraft scatter on UHF. I then set out the theory of the mechanism, arguing that it’s not so much scatter as plurality of reflections from the surfaces of the aircraft, especially the wings. I then used a path budget to demonstrate what happens when reflection occurs from a Boing 747 and then from a smaller aircraft. I ended with a demonstration of a VHF QSO requiring several aircraft to complete using data mode Q65.
To learn more about aircraft scatter as a VHF/UHF/SHF mechanism, view the presentation at https://youtu.be/qpWlbuKI47E.
This presentation was given at the regular Mid Sussex Amateur Radio Society meeting in Burgess Hill, UK and online.
Past talk – EME/moonbounce explained – see below for video
Friday 11th October 2024, MSARS and online. One of several GM8JBJ ham radio events.
The Moon is about 384,000km away (less at perigee, more at apogee). The corresponding round-trip (EME) free-space path loss for a signal is a huge 400dBi – no way anyone can bridge that gap. But the Moon is a remarkably good reflector. The result is a real total path loss of around 250dBi and that’s (just) low enough for radio amateurs to exploit our natural satellite to communicate almost globally. So how’s it done and why does it work? And more importantly, is doing EME worth all the hassle and cost? I explained all.
The presentation was aired at the regular Mid Sussex Amateur Radio Society meeting in Burgess Hill, UK, and online for anyone worldwide. The recording of the talk is available here https://hamradio.engineering/moonbounce-eme/.
Past Talk – Unscrambling the Alphabet Soup: digital modes explained – see below for video
Friday 13th October 2023 MSARS and Online. One of several GM8JBJ ham radio events.
Digital modes now offer great opportunity. Moonbounce can be done with simple antennas. New Zealand is no longer DX from the UK. And the system values have jumped anything up to 40dB (and hence the path lengths have lengthened greatly). Rare paths available for less than 1% of time are now available around 50% of time. So, what’s it all about? How do radio amateurs understand modern digital models?
The video of the presentation is available at https://hamradio.engineering/data-modes/
Past Talk – About Sporadic E – see below for video
23rd September 2022 MSARS and Online. One of several GM8JBJ ham radio events.
In summer, not all fruits in the garden are strawberries. This analogy illustrates the assumption that many radio hams make about Sporadic E propagation. Because it’s June, they assume that all VHF contacts are made via Sporadic E. This presentation strives to explain Sporadic E (Es) propagation and debunk such assumption.
Sporadic E has many variables – the Sun’s radiation, wind shear, winds and tides, the geomagnetic field, disturbance of the geomagnetic field, meteor characteristics, time, latitude, and tropospheric effects (like mountain turbulence, jet streams and thunderstorms) creating atmospheric gravity waves that propagate upwards. As a result of the many variables, it’s impossible to predict when an Es opening will occur. Es is most prevalent over the summer months and less frequent in winter.
See https://hamradio.engineering/sporadic-e/ on this site for the presentation.
Past Talk – Communication via the aurora – see below for video
12th November 2021 MSARS and Online. One of several GM8JBJ ham radio events.
Communication by radio amateurs via the aurora borealis (and indeed via the aurora australis in the southern hemisphere) can only be described as occasional. Like Sporadic E, it’s a mechanism supported when several atmospheric and geomagnetic effects align. And it occurs in the thermosphere, around 110km up, and about 50˚ to 60˚ North. But just because there’s a visible light show does not mean radio propagation will be supported. So why, and how often, do radio auroras occur? Can I participate south of the Scotland/England border? What do I have to do to exploit an aurora? How will I know if there’s an aurora in progress? How can I design my station to maximise both chances and DX outcome? And how can I predict when a radio aurora is going to happen? John answered these questions while covering the full science and practice of communications via radio auroras.
See https://hamradio.engineering/radio-auroras/ on this site for the presentation.