Ham radio in the 21st century
The first wireless communicators were by definition all amateurs. Guglielmo Marconi himself, generally regarded as the inventor of radio, once famously remarked that he considered himself an amateur. In the early days of radio, commercial, government, and amateur stations shared the same spectrum, sending broadband spark-generated transmissions modulated by on/off keying using Morse code to convey messages. This practice resulted in a horrendous amount of interference among services until the government stepped in and assigned various services to specific bands.
Government and commercial stations were assigned the supposedly more useful, less-than-1500-kHz, long- and medium-wave spectrum, and the amateurs were banished to the less-than-200m wavelengths with frequencies higher than 1500 kHz. The experts of the day regarded these bands as worthless for long-distance communications.
The amateurs soon discovered that long-distance communications were actually easier at these frequencies. New allocations were then created to give government and commercial stations some of the “good” spectrum. However, a handful of slices of the spectrum were reserved for the amateurs. In the late 1960s, amateurs laid claim to all of the apparently useless frequencies higher than 30 GHz. Since then, as technology has marched on, other services have discovered that these frequencies are useful; amateurs currently enjoy exclusive rights to the frequencies greater than 300 GHz.
Part 97 requires that amateur stations obtain licenses before they can transmit. The process for getting a ham-radio license has evolved over the years. Long ago, an applicant had to pass a rigorous technical exam that included drawing schematics from memory. The exams have changed considerably. All of the questions are now multiple-choice and cover technical, operating, and regulatory topics, and all of the questions and answers—both right and wrong—are available in the public domain. Furthermore, the governments of many countries—notably, the United States—have effectively outsourced the job of testing.
The US amateur-licensing process no longer requires knowledge of Morse code for any class of license. This requirement has historically been a major impediment for many technically skilled individuals who were interested in ham radio but who could not or would not conquer Morse code. Ironically, the portions of the bands reserved for CW (continuous-wave) operation are busier than ever, as new licensees discover that narrow-band modes are more effective for weak-signal work than are wider-bandwidth modes, such as SSB (single-sideband) voice.
Many amateurs make contacts using voice modes, primarily SSB mode on HF and FM on VHF and UHF. The signal- processing capabilities of a soundcard-equipped PC that connects to an HF SSB or a VHF FM transceiver have driven the emergence of new modes. Even a modestly equipped PC has sufficient speed to generate and decode the FSK signals for conventional radio teletype.
Experimenters have created modulation schemes and accompanying protocols, complete with forward-error correction, which enable direct keyboard-to-keyboard contacts even with low power and small antennas. The variety of FSK and PSK signals being used create unusual buzzing and chirping sounds when traveling to a speaker, and computers easily demodulate them and turn them into legible text. Some ingenious hams even use the PC’s signal-processing capabilities to emulate the signals that World War II-vintage mechanical text-to-radio systems, such as Hellschreiber, generated.
Some hams also engage in transmission of full-motion video signals—usually on VHF or UHF bands, on which sufficient bandwidth is available. Others transmit still pictures on HF, using voice-bandwidth signals and a PC. Data networks have also evolved using various systems, including TCP/IP.