Radio amateurs, after having been licenced for a while, typically tend to pick up a specialisation within the hobby. This is partly brought about by the licencing system, which allows you to do the RAE (Radio Amateurs Examination) only, and take a B licence for 50 MHz (6 m band) and up only. For the full or A licence you have to pass a 12-wpm morse proficiency test as well, which on passing allows you to use all radio bands, including those below 50 MHz. Although the full licence gives you many more bands to work on, many B licensees remain Bs forever because they are not interested in the extremely crowded shortwave bands. Similarly, many A licensees are never heard on the VHF and UHF bands. A special category is formed by the Novice licensees, who take a simplified exam (also A or B). Unfortunately, the Novice licence is not (yet) commonplace in all countries, at least not in those in which amateur radio is regulated by CEPT Recommendation T/R 61-01. The Novice licence was first used in the UK.
A distinction is also often made between amateurs who build their own equipment, and those who use off-the-shelf rigs and antennas only. That distinction does not exist because (1) it is impossible to make everything yourself cheaper than you can buy it ready-made, and (2) there is some home-brew item in any radio amateurs shack. Still on the subject of diversification, some general points will be made on the most popular specialisms available to radio amateurs.
RTTY
Plain telexing seems to have disappeared nowadays, being replaced by more intelligent systems like AMTOR (amateur telex over radio) and PACTOR. AMTOR is a synchronous 100-baud system which has two primary operating modes: ARQ (automatic repeat request) and FEC (forward error correction). Most long-distance RTTY traffic is found in the shortwave bands, particularly, in the 80 m (3.5 MHz) and 20 m (14 MHz) bands. Most radio amateurs have now got rid of old mechanical telex machines, and have taken to using PCs and special interface cards.
CW
Morse (CW) still has its staunch supporters but is definitely on the decline, being inherently slow as compared with almost any digital communication protocol. Interestingly, this mode was officially abandoned for coastguard communications not so long ago. None the less, there are still many radio amateurs who love to make very long distance contacts using their morse key and a very low power transmitter.
SSTV
Slow-scan television (J2F), too, will never be the same since the PC arrived. These days, computer-generated pictures are exchanged in colour mainly via the 20 m band, sometimes in two-way links using error-correcting systems.
Fax
Mechanical systems are rapidly being replaced by computers. A special area is formed by weather fax reception, which uses terrestrial transmitters, low-orbiting satellites (NOAA, GOES) as well as the geostationary Meteosat at about 1.7 GHz. No licence is required to receive weather fax signals, which are of great interest to amateur meteorologists. Here, as in many other areas, radio amateurs have been in the forefront of modern developments.
Amateur satellites
Radio amateurs have pioneered communication by satellite, indeed, they have for many years built and operated their own satellites. The best known ham sats are those in AMSATs OSCAR (Orbiting Satellite Carrying Amateur Radio) series, which became popular through their 2 m band transponders. A recent development is the use of satellites totally geared to packet radio communication (PACSAT). This will undoubtedly lead the way towards Microsofts initiative to commission satellites for computer communication. When these plans get off the ground, radio amateurs with experience in working via satellite will have a great technical advantage. In general, the equipment needed to communicate via satellite in the 2 m band is very simple indeed, and antenna tracking is not always necessary.