Radiofyr
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Skrevet av LA7ARA - Roger Fosland   
søndag 01. mai 2011 21:14

LA3T er ansvarlig for flere populære radiofyr.beacon_1

Fyrene er plassert på Bardufoss og drives sammen med LA6M - Midt-Troms gruppen.


 

Radiofyrene LA7SIX og LA7VHF ble installert av LA3TQ Dag og LA5TFA Åsmund i 1999 og er blitt blandt de mest monitorerte VHF-fyr i Europa.

Sommeren ble et nytt 70 MHz radiofyr satt opp for test i Tromsø, dette skal i løpet av sommeren 2011 flyttes til Bardufoss og settes i permanent drift der.


Kortversjon av teknisk informasjon

LA7VHF - 144.451 MHz - 55 W - 10-element-yagi

LA7SIX - 50.051 MHz - 30 W - 4-element-yagi

 

LA7VHF

LA7VHF is a very useful signal source for propagation studies on the 2 m band. The transmitter provides 55 W of RF power into a 10-element-yagi antenna. Since July 1997 the frequency is 144.451 MHz. The furthest observation was made in June 1992 by DB8KJ in Germany (~2300 km) through Sporadic-E-propagation. The high radiated power (500 W ERP) makes the LA7VHF beacon particularly attractive for monitoring Meteorscatter and Auroral-E propagation.

The keying sequence includes the callsign and the locator. For power saving reasons the locator is followed by a string of dots and not by a continuous carrier.

LA7VHF_1

LA7SIX

LA7SIX was the first 50 MHz beacon in Northern Scandinavia, and its the only one in Norway. The transmitter provides 30 W of RF power on 50.051 MHz into a 4-element-yagi antenna. The furthest observation was made in February 1992 by CN8ST in Morocco (~4200 km) through F2-propagation.

50 MHz is most attractive for newcomers, because of frequent Sporadic-E and Aurora-E openings and the small budget for equipment required.

la7six_1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VHF propagation in Northern Scandinavia

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.

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 many contacts. 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.

 
70 MHz radiofyr i Tromsø PDF Skriv ut E-post
Skrevet av LA5TFA Åsmund /LA7ARA   
søndag 12. desember 2010 09:20

LA7VHF_antenner_2_600

Med hjelp fra LA5QEA Ralf, DF7KF Dithmar og LA0BY Stefan satte LA5TFA Åsmund opp Norges første 70MHZ radiofyr i Tromsø 6.juni 2010

 

Kallesignal: LA7VHF,
Lokator: JP99kq Kvaløysletta, (midlertidig)
Frekvens:70081.0