Amateur Radio Propagation Studies
Science, research, engineering, operating
Very special background images for your computer screen
Demonstrate the fascination of VHF radio propagation to your friends and family members
Download your prefered image to be used as background wallpaper on your computer screen. Click that image and follow the instructions of your computer manual for installation.
There are many places on Earth, e.g. mountaines and planes, glaciers and deserts, hugh cities and dull villages - in the practice of VHF dxing all this places have something in common, i.e. a six digit alphanumberic Maidenhead grid locator information describing the geographical position. The above images represent an attempt at harmonizing this "technocratic grid system" with the beauty and complexity of the real world.
See the moon's echo depth (yellow) resulting from the curvature of the moon: radar pulses reflected by regions close the lunar limb travel a longer distance (twice the moon's radius) back to Earth than signals reflected by the moon's leading edge. However, radar returns from the lunar limb are attenuated by more than 40 dB compared to echoes originating from the moon's disk center, i.e. the moon shows a limb darkening at radio wavelengths which does not exist at optical wavelengths. In consequence, radiowaves, unlike light and infrared radiation, are reflected back to the Earth from a small region at the center of the visible disk (green). Using high operating frequencies (10 GHz) and digital noise reduction methods, powerful EME stations may however detect the moon's echo depth at least partially, perhaps. In science, Earth-based radar systems are used, e.g., to analyse the lunar topography with radar interferometry techniques, see the elevation model of the Tycho crater measured by the Deep Space Network.
In this wallpaper, you may find real moon echoes recorded by Leif, SM5BSZ, using SM5FRH's X-yagi array in the 2001 ARRL contest. The diagram displays the first 90 kHz of the 2m band (from left to right) and each of this broken lines indicates an EME signal (from bottom to top). View the box on right extracting a small segment from the wallpaper - can you see what it is? Right, it displays a sequence of dits and dahs ("CQ") and you may find many more EME signals in the wallpaper image. If you wish to learn more about this fascinating recordings, please refer to Leif's web site. The wallpaper also displays Ed's (N5BLZ) 16 x 18el yagi array which is designed for 144 MHz moonbounce communication. I am grateful to Leif and Ed for granting the permission of using their material and photographs in this wallpaper.