ON4KDE is a Radioamateur Callsign
The radiomateurs in the world have callsigns which permit to identity them
Every country uses a prefix
For example :
ONxxxx is a belgian station Fxxxx is a french station Gxxxx is an english station
the countries list is very long
A click on the button will show you what is used in the world
For Belgian station the prefix rules are :
ONL Listening station, can not transmit
ON1 150 watts in VHF, UHF et 50 watts in HF
ON2 VHF et UHF only with a maximum power of 50 watts
ON3 Same as ON2 plus 10 watts in HF. This is typically a beginner station
ON4 ON5 ON6 ON7 ON8 this is the highest licence in Belgium, all bands and 1000 watts.
note that the numbers 4 to 8 means nothing else than disponibility on date of licence
ON9 Not European citizen living in Belgium
The letters which follow are often the initials of the radioamateur name
Thus ON4KDE is : a belgian station (ON) with full licence (4) and with initials KDE
Most of the countries in the world have contracted a reciprocity agreement
the owner of a valid licence may use his radio to transmit while in another country
in this case the standard rule is to use the local prefix followed by the radioamateur national callsign
For example if ON4DKE transmits while in France he should use F/ON4KDE as callsign
If F4ABC transmits while in Belgium he should use ON/F4ABC as callsign.
Note that some countries require a special authorization.