Ham Amateur Radio Technician Practice Exam 2026 – The Complete All-in-One Guide to Exam Success

The correct mode used for sending RTTY (Radio TeleType) signals via AFSK (Audio Frequency Shift Keying) with an SSB (Single Sideband) transmitter is LSB, which stands for Lower Sideband.

When RTTY is transmitted using AFSK, the audio tones that represent the binary data are modulated onto the SSB carrier frequency. For typical amateur radio applications, the lower sideband is the preferred mode for RTTY transmissions. This is largely due to convention and historical preference in the amateur radio community where LSB is commonly used for frequencies below 10 MHz, and USB (Upper Sideband) is used for frequencies above 10 MHz.

While USB may also be used in some cases, most operators stick to LSB for RTTY emissions, especially on traditional HF bands. Additionally, the most common amateur data modes, including RTTY, were standardized around this practice, making it an essential aspect of operating procedures within ham radio.

The other options, such as CW (Continuous Wave) and FM (Frequency Modulation), are used for different types of communications and do not apply to RTTY transmission. Therefore, LSB is recognized as the appropriate and conventional mode for RTTY signals via AFSK