- AM (Amplitude Modulation - double sideband, full carrier) is the oldest form of voice modulation. A CW carrier signal is controlled (modulated) by an audio voltage, so that the amplitude of the radio carrier ranges from zero (at negative audio peaks) to 200% (at positive audio peaks). Generation and reception of traditional AM can be done with relatively simple circuits, and it is still in use by a small, but hardy group of amateurs. (See the AM Phone page.) Nevertheless, most ham voice activity on HF has moved to SSB (see below).
- Digital Voice is a new technique built around analog to digital converters and codecs that sample a voice signal, compress it, and transmit it as a bit stream. Like other digital media, digital voice offers interference free communications if the radio signal is strong enough to overcome the general noise and interference level.
- FM (Frequency Modulation) is the voice mode of choice for local VHF / UHF operations, fixed or mobile, simplex or repeater based. It offers good performance with simple equipment requirements. The audio signal controls (modulates) the frequency of the transmitter over a small range.
- SSB ("sideband", Single Sideband Suppressed Carrier) is the descendant of traditional AM. Compared to AM, SSB requires less than half the bandwidth and it offers much more "talk power", since the unnecessary carrier and second sideband are not transmitted. SSB requires more frequency stability and somewhat more complex circuitry than AM, but essentially all mainstream amateur gear for the HF bands now supports SSB voice.
- Practical HF Digital Voice
QEX May 2000, pp. 3-8
High-quality voice communications using modems.
- International Digital Audio Broadcasting Standards: Voice Coding and Amateur Radio Applications
QEX January/February 2003, pp. 49-56
A digital-voice standard for broadcast and Amateur Radio.
- PTC: Perceptual Transform Coding for Bandwidth Reduction of Speech in the Analog Domain, Pt 1
QEX May/June 2000, pp. 9-12
A new method for optimizing the bandwidth of phone signals using sound perception.
- PTC: Perceptual Transform Coding for Bandwidth Reduction of Speech in the Analog Domain, Pt 2
QEX March/April 2001 pp. 9-17
- JAIA's Universal Standard D-Star
CQ Ham Radio Magazine. Reprinted with permission.
A overview of a digital communication standard as presented at the At HAM Fair 2001, in Japan.
- Digital Voice: The Next New Mode?
QST January 2002, pp. 28-32
A brief tour of this technology and it’s place in Amateur Radio.
- Digital Voice: An Update and Forecast
QST February 2002, pp. 38-41
What hams are doing with digital voice now and what about the future?
- Amateur Radio and the Rise of SSB, Gil McElroy, VE3PKD
QST Jan., 2003
- Advanced Technology in Amateur Radio video - Talk given by Doug Smith, KF6DX, QEX Editor at Georgia Tech, March 10, 2003. Windows WMV format, 110 minutes.
- Digital/Analog Voice Demo
This is a comparative demonstration of some digital and analog voice transmission alternatives for the power-limited amateur satellite channel.
- RAC Digital Speech Modes page
Links to tutorials and other information on Digital Speech
- Digital Voice Systems
AMBE vocoder chip manufacturer
- The Start of the Digital Revolution
SIGSALY Secure Digital Voice Communications in World War II
- Digital Voice Project
K3TU Temple University Amateur Radio Club
- TAPR Digital Voice Forum
Slides from the Digital Voice Forum at Dayton Hamvention 2002.
- What is Single Side-band?, SGC Inc.