What Is SSB?

A few weeks ago a ham gave me a report on my 40 meter SSB signal quality. He told me that my carrier was fine but my audio was low. That is when it became obvious to me that either I had a problem with my transmitter or he did not understand what SSB was and I think it was the latter.

Normally the term SSB is used to mean Single-SideBand suppressed carrier (SSB-SC). In other words, if the transmitter is operating correctly there is no noticeable carrier. It is possible and legal to send a SSB signal with carrier but I have never heard this done on the ham bands.

When two alternating current signals are combined in a non-linear circuit they will product heterodynes of the sum and the differences of the signals.

(Heterodyne is an English word that is composed of two words of Greek origin. the first part, hetro, comes from the Greek word heteros [ἕτερος] which means another of a different kind. The second part of the word is dyne which comes from the Greek word dynamis [δύναμις]. The English word dynamite is also from δύναμις. It means force, power, or energy. When the two words are put together it means an energy or signal of a different kind or different frequency in this case.)

So if there is a 1 MHz signal mixed with a 1 KHz signal it will produce a third signal equal to the sum the two (1 MHz plus 1 KHz) or 1,001 KHz called the upper sideband. It will also produce an other signal equal to the difference of the two or 999 KHz (1 MHz minus 1 KHz) called the lower sideband. If the 1 MHz carrier is transmitted with the two side bands it will result in an Amplitude Modulated signal with a 1 KHz tone.

To send a SSB signal the carrier and one of the sidebands must be removed. The carrier is normally removed in the balanced modulator and the unwanted side band is removed by a filter.
There is a process of removing the carrier and unwanted sideband by phasing networks but I do not know of any modern transmitter that uses this process.

So when giving a signal report on someone’s SSB signal do not say the carrier is fine because if it has a carrier that is not good and they need to be told.

 

 

 

 

 

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