Alex Discovers Amateur Radio

14 More than you might think. A good hailstorm will bounce and scatter radio signals. Even rain clouds can affect signals. More unusual forms of propagation include scatter from meteor showers, and bouncing signals off the moon. Very high gain antennas are usually needed to reliably pick up the weak return signals. DSP has improved amateur radio performance in recent years. It makes it much easier to isolate the signal you want to listen to and eliminate QRM (interference). Bill, what was the other way you said could help us hear signals more clearly – changes in the atmosphere. It could have been favourable atmospheric conditions. What does the atmosphere have to do with radio signals? Very High Frequencies 144 MHz and above But the biggest way the atmosphere affects radio signals isn’t by weather but by the different properties of the ionised layers in the sky. There are several different layers in the ionosphere 70 to 400 km high. Radio signals usually travel in straight lines. Very High Frequency (VHF) signals usually travel directly into space but lower frequencies can be bent back to earth by the ionosphere. There is also a ground wave close to the earth’s surface. Micro-chips are now so powerful they can replace many processing parts of a radio. Software upgrades can later be downloaded. Higher frequencies “bend” differently to low frequencies Range covered in one hop at 7 MHz Range covered in one hop at 14 MHz Ground Wave Ground Wave