VHF propagation in Northern Scandinavia
LA0BY, last updated 04.04.2002
North of the Arctic Circle, the VHF propagation situation is probably very different from what most other VHF amateurs in Central Europe are used to. During contests the 144 MHz activity is zero and long distance tropospheric ducting does not occur due to the high mountains.
In more than six years of (admittedly sporadic) activity from Northern Scandinavia the author of this page has not had a single contact via Aurora, neither on 144 MHz nor on 50 MHz. Aurora is possible though, and has been observed by others, but is really rare at latitudes above 67 degrees north.
Sporadic-E with its strong and stable signals is easy to recognize, but on 144 MHz even more seldom at northern latitudes. Years ago some British amateurs were monitored in Tromsø (JP99LP) with hand-held transceivers in FM, and in May 1991 the LA7VHF beacon was copied by DK1KO for 30 minutes with a solid 579 signal. LA1MFA in JP99 has worked into Southern Sweden once. On 50 MHz the chances for contacts via Sporadic-E are good during the summer months, even late at night.
A hybrid mode, among amateurs usually called Aurora-E, seems to be very frequent between May and August, peaking in June and July. Because of the at least on 144 MHz significant signal audio characteristics and diurnal variation of observation it is suspected that Aurora-E is identical with what scientists call Polar-Mesosphere-Summer-Echos (PMSE). Although several research programmes have been executed, the phenomenon is still not understood in all details. Aurora-E is one of the few remaining subjects where amateur observations may well contribute to ionospheric science. The amount and distribution of possible monitoring stations is large compared to scientific installations and reports from radio amateurs would certainly help to improve statistics.
UA1ZCL near Murmansk has frequently worked via Aurora-E down to Denmark and Northern Germany, and also LA0BY has made manycontacts. The propagation seems to occur often before, during or after periods of strong Aurora from 06-10 UT and 20-00 UT, but openings in the early afternoon have also been noticed. Probably caused by reflection on rapidly moving thin sloping layers at heights around 85 km, the signal shows rapid fading and often appears weak, even though the fieldstrengths may be quite reasonable. The position of the reflective layers may follow that of the auroral oval. A location above Oslo at 58 degrees North will allow for contacts between Northern Scandinavia and Central Europe.
Earlier reported contacts between SM2CEW, GM4IPK and other high power stations, also at more southern latitudes, gave rise to speculations upon some kind of Ionoscatter propagation. In a spectacular event, DF9PY/p in JO30JF managed to work SM2EKM and OH5LK in June 1989, using only a 2 x 10-element-yagi and 180 W RF power. The distance to SM2EKM was 1947 km. On the same day also propagation via Aurora and also Sporadic-E was noticed, at times even simultaneously. However, it seems to be difficult to distinguish between Aurora-E and Ionoscatter. If there really is a difference, Ionoscatter could have a higher altitude of reflection.
50 MHz is most attractive for newcomers, because of frequent Sporadic-E and Aurora-E openings and the small budget for equipment required. The only thrill that keeps the 144 MHz interest alive in Northern Scandinavia is MS and Moonbounce. Unfortunately the demand on experience, knowledge and equipment is rather high for successful operation in these modes.
Additionally, the standard Norwegian license limits the RF power above 144 MHz to 300 W RF, which is definitely not enough for even a moderate EME success. However, under certain circumstances an extraordinary permission to run 1 kW RF has been given by the Norwegian Telecommunications Authority on a non-interference basis.
With only very few VHF amateurs active from locations north of the Arctic Circle, beacons play an important role in propagation monitoring. TheLA7SIX and LA7VHF beacons, which are operational since April 1991, have contributed considerably to the VHF activity. More people in central Europe seem to turn their beams towards the North when there is a chance to listen to a signal. Other useful beacons are OH9SIX in Northern Finland and JW7SIX on Svalbard. More beacons can be found in the latest list of Norwegian beacons.
Due to the large distance to the European areas with high activity, and the occurence of special propagation modes, stations in Northern Scandinavia have a good chance of establishing new distance records.