Question
Which mode is normally used when sending RTTY signals via AFSK with an SSB transmitter?
Answer Options
- A) USB
- B) DSB
- C) CW
- D) LSB
Correct Answer: D
Explanation
When using an Single Sideband (SSB) transceiver to transmit digital modes like RTTY (Radio Teletype) using Audio Frequency-Shift Keying (AFSK), a specific convention is followed to place the transmitted signal in the correct spectral location. The amateur convention dictates that AFSK-based digital modes, when operated on HF bands below 10 \text{MHz}, should use the Lower Sideband (LSB) setting on the transceiver.
On HF bands above 10 \text{MHz}, the Upper Sideband (USB) setting is used. This is part of the same operating convention as voice SSB and ensures all operators can correctly tune into the signal. The choice is based purely on convention, not technical necessity of the AFSK modulation itself, as long as the total bandwidth is within limits.
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