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  SSB (Single Sideband) BUY AMERICAN!

 

Single-sideband modulation (SSB) or Single-sideband suppressed-carrier (SSB-SC) is a refinement of amplitude modulation that more efficiently uses electrical power and bandwidth.

 

Amplitude modulation produces a modulated output signal that has twice the bandwidth of the original baseband signal. Single-sideband modulation avoids this bandwidth doubling, and the power wasted on a carrier, at the cost of somewhat increased device complexity.

 

Only the sidebands contain the information being transmitted. Both the upper and lower sidebands are identical. You only need one of them to extract the modulation information. The RF carrier, which does not contain any information, requires two-thirds fo the total transmission power. By not transmitting the carrier an one of the sidebands, the transmission efficiency is greatly increased and the bandwidth required is decreased.

 

On HF and by agreements worldwide, all stations transmitting SSB use LSB on 160 meters through 75 meters, USB on 60 meters, back to LSB on 40 meters and then all bands above 40 meters use USB. This agreement makes life easy when switching bands. Every one knows which modes are used on which bands.

 

Since the fidelity of the SSB voice transmission has been altered somewhat through various filters in the process of producing the sideband that is not too wide, usually only the most important portions or characteristics of the voice frequencies needed to communicate are allowed through, and this causes the lack of true AM or FM fidelity to the transmission, but the communication, (understandable), portions of the voice characteristics remain, which is all that is needed in the first place. The information contained in the average human voice needed to understand the voice is contained within about the first 3000hz of the human hearing range. Frequencies of the human voice beyond this range are not needed for communication purposes and are filtered out in the modulation process. So the average bandwidth of a SSB signal is about 3000hz wide with all of the voice characteristics needed within that range to be understandable.

 

For further reading, I would like to suggest the Wikipedia page the discusses Single Sideband Modulation as well as the information provided at HamUniverse.com.

 

An example block diagram of a SSB transmitter is shown on the right.

SSB Transmitter

An example graphic of the two sidebands and the carrier is shown to the right

AM SSB

One of the transmitters I own is the Flex Radio 3000 Software Defined Radio. One of the cool features is the Panadapter view. This gives me the ability to directly see a SSB modulated signal so I can zero in on a QSO.

SDR

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