Ham Radio General Class Practice Test

Which mode is normally used when sending an RTTY signal via AFSK with an SSB transmitter?

1. USB

2. DSB

3. CW

4. LSB

The correct answer is: LSB

When sending an RTTY (Radio Teletype) signal using AFSK (Audio Frequency Shift Keying) with an SSB (Single Sideband) transmitter, LSB (Lower Sideband) is typically used. This is because RTTY is often transmitted in a frequency range where LSB is more commonly utilized, especially in the amateur radio bands where RTTY operation occurs. In AFSK, the audio tones used to represent the RTTY symbols are generated and fed into the SSB transmitter, which modulates the tone signals onto the carrier frequency. For lower frequency RTTY operations and in many regions, operators prefer LSB over USB (Upper Sideband) because it aligns well with standard operating practices for various digital modes. It is also more practical for station compatibility and to avoid frequency overlaps in busy bands. Using LSB helps ensure clarity and performance for decoding and receiving RTTY signals, as it is more likely to be in line with other operators' setups and practices on those specific frequencies. Thus, LSB is the mode that is conventionally used in this context.