The many facets of amateur radio attract practitioners with a wide range of interests. Many amateurs begin with a fascination with radio communication and then combine other personal interests to make pursuit of the hobby rewarding. Some of the focal areas amateurs pursue include radio contesting, radio propagation study, public service communication, technical experimentation, and computer networking.

Hobbyist radio enthusiasts employ a variety of transmission methods for interaction. The primary modes for vocal communications are frequency modulation (FM) and single sideband (SSB). FM is recognized for its superior audio quality, whereas SSB is more efficient for long-range communication under limited bandwidth conditions.

Radiotelegraphy using Morse code, also known as "CW" from "continuous wave", is the wireless extension of landline (wired) telegraphy developed by Samuel Morse and dates to the earliest days of radio. Although computer-based (digital) modes and methods have largely replaced CW for commercial and military applications, many amateur radio operators still enjoy using the CW mode—particularly on the shortwave bands and for experimental work, such as Earth–Moon–Earth communication, because of its inherent signal-to-noise ratio advantages. Morse, using internationally agreed message encodings such as the Q code, enables communication between amateurs who speak different languages. It is also popular with homebrewers and in particular with "QRP" or very-low-power enthusiasts, as CW-only transmitters are simpler to construct, and the human ear-brain signal processing system can pull weak CW signals out of the noise where voice signals would be totally inaudible. A similar "legacy" mode popular with home constructors is amplitude modulation (AM), pursued by many vintage amateur radio enthusiasts and aficionados of vacuum tube technology.

Demonstrating a proficiency in Morse code was for many years a requirement to obtain an amateur license to transmit on frequencies below 30 MHz. Following changes in international regulations in 2003, countries are no longer required to demand proficiency. The United States Federal Communications Commission, for example, phased out this requirement for all license classes on 23 February 2007.

Modern personal computers have encouraged the use of digital modes such as radioteletype (RTTY) which previously required cumbersome mechanical equipment. Hams led the development of packet radio in the 1970s, which has employed protocols such as AX.25 and TCP/IP. Specialized digital modes such as PSK31 allow real-time, low-power communications on the shortwave bands but have been losing favor in place of n…

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Radio transmission permits are closely controlled by nations' governments because radio waves propagate beyond national boundaries, and therefore radio is of international concern.

Both the requirements for and privileges granted to a licensee vary from country to country, but generally follow the international regulations and standards established by the International Telecommunication Union and World Radio Conferences.

All countries that license citizens to use amateur radio require operators to display knowledge and understanding of key concepts, usually by passing an exam. The licenses grant hams the privilege to operate in larger segments of the radio frequency spectrum, with a wider variety of communication techniques, and with higher power levels relative to unlicensed personal radio services (such as CB radio, FRS, and PMR446), which require type-approved equipment restricted in mode, range, and power.

Amateur licensing is a routine civil administrative matter in many countries. Amateurs therein must pass an examination to demonstrate technical knowledge, operating competence, and awareness of legal and regulatory requirements, in order to avoid interfering with other amateurs and other radio services. A series of exams are often available, each progressively more challenging and granting more privileges: greater frequency availability, higher power output, permitted experimentation, and, in some countries, distinctive call signs. Some countries, such as the United Kingdom and Australia, have begun requiring a practical assessment in addition to the written exams in order to obtain a beginner's license, which they call a Foundation License.

In most countries, an operator will be assigned a call sign with their license. In some countries, a separate "station license" is required for any station used by an amateur radio operator. Amateur radio licenses may also be granted to organizations or clubs. In some countries, hams were allowed to operate only club stations.

An amateur radio license is valid only in the country where it is issued or in another country that has a reciprocal licensing agreement with the issuing country.

In some countries, an amateur radio license is necessary in order to purchase or possess amateur radio equipment.

Amateur radio licensing in the United States exemplifies the way in which some countries award different levels of amateur rad…

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Amateurs use a variety of voice, text, image, and data communication modes the over radio. Generally new modes can be tested in the amateur radio service, although national regulations may require disclosure of a new mode to permit radio licensing authorities to monitor the transmissions. Encryption, for example, is not generally permitted in the Amateur Radio service except for the special purpose of satellite vehicle control uplinks. The following is a partial list of the modes of communication used, where the mode includes both modulation types and operating protocols.
• Amplitude modulation (AM)
• Double Sideband Suppressed Carrier (DSB-SC)
• Independent Sideband (ISB)
• Single Sideband (SSB)
• Amplitude Modulation Equivalent (AME)
• Frequency modulation (FM)
• Phase modulation (PM)
• Amateur Television (ATV), also known as Fast Scan television
• Slow-Scan Television (SSTV)
• Radiofax
In former times, most amateur digital modes were transmitted by inserting audio into the microphone input of a radio and using an analog scheme, such as amplitude modulation (AM), frequency modulation (FM), or single-sideband modulation (SSB). Beginning in 2017, increased use of several digital modes, particularly FT8, became popular within the amateur radio community.
• Continuous Wave (CW), usually used for Morse code
• Automatic Link Establishment (ALE)
• AMateur Teleprinting Over Radio (AMTOR)
• PACTOR
• Radioteletype (RTTY)
• Hellschreiber, also referred to as either Feld-Hell, or Hell
• D-STAR
• Digital mobile radio
• Fusion (Yaesu own mode)
• GTOR
• Discrete multi-tone modulation modes such as Multi Tone 63 (MT63)
• Multiple Frequency-Shift Keying (MFSK) modes such as
• Packet radio (AX.25)
• Phase-Shift Keying
• CLOVER
The following "modes" use no one specific modulation scheme but rather are classified by the activity of the communication.
• AllStarLink (AllStar / ASL)
• Earth-Moon-Earth (EME)

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