Types of modulations usable by the French hams
Almost every types of modulation are authorized with the French radio hams:
Morse telegraphy was the first system used to transmit information, it is simplest and most powerful in the very difficult situations of traffic (jammings, interferences, weaks signals); it is always used today and comprises enthusiastic fans.
Other telegraphic modes appeared since, without supplanting the simple key of origin, some based on automatic transmission and reception, like the teleprinter or the data transmissions.
The amplitude modulation was then the first used type of audio modulation, it is still used with long wave braodcast transmitters for example, this type of modulation is not used any more today by the amateurs who prefer now two other modes:
On the decametric waves, the single band (SSB) is almost only used, it is less pleasant to listrn, but much more effective in the difficult situations of traffic.
On metric waves, it depends on the type of traffic : the narrow band frequency modulation is retained for the quality of the modulation obtained in short distance traffic, where the signals are strong and not very affected by interferences. To search distant or weak stations, SSB is also used as ondecametrics.
The pictures transmissions use different technologies according to frequency bands used:
In decametric waves, the pictures transmissions are done at slow speed, a fixed image requires a few seconds to pass from a continent to the other, it is the fax simile and the slow scan television (SSTV).
On the decimetric frequencies and beyond one can moreover use normal television (ATV for Amateur Tele Vision), strictly identical to the broadcast TV we receive on our family television sets.
For those which do not know amateur radio, see:
Frequency bands propagation types of traffic organizations
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