MARS

Amateur Radio Society

Technical Presentation - "Propagation"

2024 May 25 OM Raghav VU3VWR

The quarter’s members’ meeting of MARS Amateur Radio Society which was held on Saturday, 25th May, 2024 at 6.15 pm IST (1815hrs) in the “Vivekananda Hall” of the P.S.High School Campus, Mylapore, Chennai. After the usual formalities and pleasantries, it was now time for the main event. OM Arun Kumar - VU2BBF introduced the speaker of the evening, OM Raghav – VU3VWY.

OM Raghav VU3WVY made a very informative presentation about Propagation. He explained the behaviour of radio waves as they travel through the various parts of the atmosphere. He narrated the factors which affects propagation, viz: reflection, refraction, absorption, diffraction, polarization and scattering. He then explained how radio waves are bent (refracted) by the ionosphere based on the ionization level of the layer and wavelength of the signal. He also added that signals with smaller wavelength tend to bend less and very high frequency and above almost never bend.

He beautifully elucidated about the various layers such as troposphere, stratosphere, mesosphere, thermosphere and finally the ionosphere which ranges from 10 kilometres to 280 kilometres with a colourful graphical diagram and also the distance of the layers from earth for the “D”, “E” and “F” layers. He also clarified how different signals are reflected or absorbed by ionospheric layers at different times of the day.

OM Raghav touched upon the concept of “Greyline” - which is defined as a line around the world that separates the regions receiving daylight and regions in darkness. He also told us about long and short path for Dxing. There was an explanation about solar indices, solar cycle, solar flux & sunspots and how it affects the communication. Finally, the presentation was concluded with techniques of earth to moon communication. The members, on their part, also raised very interesting questions and returned home with satisfying clarifications.