In the radio frequencies used by the worldwide Ham Radio, are used some particular modes. A mode, is a special kind of radio wave modulation.
The modulation process, is an electronic process, in which the information (like voice for example) is "mixed" to the carrier (the radio wave) and then, after more electronic processes, sent to the antenna for the trasmitting.
Of course there is a reverse process, useful to extract from the radio wave the desired information.
If the information is a simple human voice, we may use the following modes:
- AM=Amplitude Modulation (the oldest and firt radio trasmission mode)
- FM=Frequency modulation (like that used by Hi-Fi radios, trasmitting on 88-108 MHz)
- SSB=Single Side Band (more effective system to carry the voice over a radio wave)
If the information is a digital datas, then the modes may be:
- CW=Continuos Wave, that is the "old Morse code" over the radio. This is the very first radio mode used by the men. It is wide used, since it is the best system when there are worst radio conditions.
- RTTY=Radio Tele Type, that means "the oldest teletype writer", this mode is now wide used, since it is very easy to implement with hardware or software
- PSK=Phase Shift Keying, a digital mode, that has a very big advantage over the others, like the less power required for a transmission.
- Packet= this mode permits to exchange data using small packet of data. Each frame (little packet) contains the data exchanged and a set of data that are in the head and in the tail of the packet, used to recnognize the owner and the receiver.
There are also other modes, like the SSTV (Slow Scan TV), FAX (the same as the usual Faxes, but sent via radio), the TCP/IP over radio, and more.
To hear or decode a particular mode, of course the receiver and the transmitter must use the same mode. Elsewere it is impossible to exchange the information between two radio (or TV) stations.