Q & A: How far you can turn the dial when transmitting in SSB voice mode?

Time and again the question arises as to how far you can turn the tuning knob when transmitting in SSB voice mode. Up to the edge of the band range? Using the 60 m band as an example, we will discuss the question here.

According to WRC-15, the range from 5351.5 to 5366.5 kHz, also called the “5 MHz band”, is allocated to the amateur radio service on a secondary basis. So, for example, are radio amateurs allowed to transmit on 5366.0 kHz within the WRC-15 60 m band in USB? [1]

The so-called “dial frequency” indicates only the frequency of the carrier suppressed in SSB. However, the modulation range for USB extends up to 3.0 kHz higher. That means 5366.0 kHz + 3 kHz = up to 5369.0 kHz. This means that a large part of the signal is outside the range assigned to the amateur radio service (see diagram, right signal, in red)! And: parts of the modulation spectrum cover the section intended for “narrow band weak signal modes”, such as WSPR. And thus leads to interference.

Therefore, the band plan indicates in the “notes”, that in the case of the 60 m band in USB, the highest “dial frequency” to be set is 5363 kHz (diagram, left signal, in green). Here the whole range of the modulation spectrum is below 5366.0 kHz. And thus both within the band and outside the “weak signal narrow band mode” range.

The same applies to the 20 m band: The highest frequency to be set in USB would be 14,347.0 kHz — i.e. 3 kHz below the upper band limit.

[1] Note: Individual countries have allocated a larger frequency range to the amateur radio service due to Radio Regulations Article 4.

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