Single-sideband modulation (SSB)
SSB
SSB linksSingle-sideband modulation (SSB) is a refinement of the technique of amplitude modulation designed to be more efficient in its use of electrical power and bandwidth. It is closely related to vestigial sideband modulation (VSB) (see below).
Amplitude modulation typically produces a modulated output signal that has twice the bandwidth of the modulating signal, with a significant power component at the center carrier frequency. Single-sideband modulation improves this, at the cost of extra complexity.
The best way of thinking of SSB modulation is to first consider an amplitude modulated signal. This will have two frequency-shifted copies of the modulated signal (the lower one is frequency-inverted) on either side of the remaining carrier wave. These are known as sidebands: either upper sideband (USB) or less commonly lower sideband (LSB).
To produce an SSB signal, a filter removes one of the sidebands. Most often, the carrier is reduced (suppressed) or removed entirely. What remains still contains the entire information content of the AM signal, using substantially less bandwidth and power, but cannot now be demodulated by a simple envelope detector.
An alternate method of signal generation has been gaining popularity recently in part due to the availability of low-cost digital signal processor (DSP) systems. To generate an SSB signal with this method, first two versions of the original signal are generated which are mutually 90° out of phase, usually by implementing a Hilbert transformer in a DSP. Each one of these signals are then mixed with carrier waves that are also 90° out of phase with each other. By either adding or subtracting the resulting signals, this can generate a lower or upper sideband signal.
The front end of an SSB receiver is the same as that of an AM or FM receiver, consisting of a superheterodyne RF front end that produces a frequency-shifted version of the radio frequency (RF) signal within a standard intermediate frequency (IF) band.
To recover the original signal from the IF SSB signal, the single sideband must be frequency-shifted down to its original range of baseband frequencies, by using a product detector which mixes it with the output from a beat frequency oscillator (BFO).
For this to work, the BFO frequency must be accurately adjusted. If the BFO is mis-adjusted, the output signal will be frequency-shifted, making speech sound strange and "Donald Duck"-like.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Single-sindband_modulation".
- 7 MHz SSB Transceiver - Circuit diagram and description of 7 MHz Ham Radio SSB Transceiver.
- Northern Lights Radio Society VHF-SHF Club (MN) - Group consisting of Upper Midwest operators active in weak signal (SSB/CW) work on the VHF, UHF, and Microwave bands. Includes meeting schedule, and conventions.
- N5KDA Ham Radio Page - A beginners guide to working SSB Meteor Skeds on 144Mhz
- High Fidelity Amateur Transmission - Information for SSB and ESSB audio transmitter, receiver and Recording/Playback for Amateur Radio.
- Microwave Directory - SSB & CW amateur radio operators in the bands 1GHZ and above. Registration required.
- Ham Radio Circuits - Circuit diagrams of Ham Radio equipment, including 7 MHz SSB Transceiver, AM, FM, DSB transmitters, FSM, Dummy load, Antenna, and filters.
- EA3QP Ham Web - Amateur radio web, devoted to SSB audio, QSL information, clusters, ITV, and useful links to another HAM webs.
- SB-10 SSB Adapter - WB6FZH has a picture and technical information on the Heathkit SB-10 SSB Adapter.
- AM/SSB/FM digital demodulator - Sources and description of a EVM56002 program that demodulate AM,SSB and FM in the digital domain
- Small Wonder Labs - Supplier of SSB and CW transceiver kits including DSW and PSK31 tranceivers.
- SB-101 transceiver - A brief history and technical run-down on the Heathkit SB-101 SSB/CW Transceiver by WB6FZH.
- 2 Meter Loop - Page contains pictures and plans for 2 Meter Loop for use on ssb
- K8EOP 5-band SSB transmitter - Site describes the rig built by this 'silent key', and it shows pictures and a description. Thanks to Al, W8UT.
- Siltronix 1011 - Information and modifications to the famous Siltronix line of 10-meter SSB transcievers.
- Collins KWS-1 and 75A4 - Pictures and information about this classic SSB pair.
- Early History of Yaesu Musen in Australia - This site gives an insite into the marketing of Yaesu Musen SSB equipment on the Australian Amateur Radio market in the early 1960's.
- N4OZI Boatanchors - Vintage AM & SSB amateur radio equipment.
|