Unusual HF Propagation Phenomena

Earthrise from Apollo 8 (NASA)

My blog has just been updated by migrating posts from my old web site containing a collection of audio samples from unusual HF propagation phenomena. They range from round-the-world propagation (delay 138 ms) to ducted transmission in the magnetosphere (delay ~140-300 ms) ending with moonbounced 7 MHz signals (delay 2.39 sec).

The posts are:

• Magnetospherically ducted echo
• Three paths from Japan to Norway along the grayline
• Propagation via aurora reflection
• Polar flutter
• Moonbounced echoes on 6792.5 and 7407.5 kHz

Aurora, 50 MHz and the Elecraft P3

Tonight had nice aurora conditions on 6 meters due to a geomagnetic storm. The Elecraft K3/P3 combo did an excellent job in showing how wide the bandwidth of these CW signals has become after having been reflected off the aurora.

The first image shows the green cursor on SM7FJE's signal, the bandwidth is almost 1 kHz.

Propagation via aurora reflection

Northern Lights in Tromsø, Norway 

Here is a recording of the Swedish station SM6CNN in contact with me on 29. October 2003, 22:42 UTC on 28.024 MHz. The direct distance is about 275 km.

Note the noise-like signal which is typical for signals that have been reflected off the aurora on the higher HF and on VHF frequencies. There was a strong geomagnetic disturbance that day with the K-index at Dombås, Norway reaching a value of 9 which explains the occurrence of aurora reflection.