19 May, 2014

Nice, watery CW signals from Alaska

 Great circle path between Anchorage and Oslo
Here's what a transpolar signal sounds like (click here to listen) and looks like (below). This one has traveled from Anchorage, Alaska to Oslo, Norway.

The characteristic sound of a CW signal that has passed over a moderate geomagnetic disturbance (Kp = 2) isn't too hard to recognize with a little practice. There is also some static on this short recording as we had a local thunderstorm coming in with the first summer days here.

The great circle distance between the two cities (actually their two airports) is 6446 km as illustrated by GPSVisualizer. Anchorage and Oslo are about at the same latitude, 61° N and 60° N, respectively. As they are at longitudes 149° W and 10° E, there is a difference of 159 ° - almost 180 ° - and this means that the signal almost passes directly over the North Pole, although a bit hard to see on the projection used in the map.

 "TU KL7SB UP", 1550 UTC, 19 May 2014, 18 MHz
There is rapid fading, or flutter, as seen e.g. from the large level difference between the two initial dots in "U". Also the dah-dih-dah pattern of the "K" has more or less merged into each other in the image, but not in the audio, as this is caused by a static crash.

It was recorded just after my contact with KL7SB on 18 MHz today from my Elecraft K3 using Audacity® which is a free, open source, cross-platform software for recording and editing sounds.

1 comment:

  1. On the Amateurradio.com version of this article there was a comment about the difficulty of copying at this speed. Here’s therefore a half speed version which should be easier to decode: KL7SB half speed.

    Audacity has an Effect mode where the Tempo can be changed. In this case it gives some artifacts, probably due to the flutter in the original version.