An MF-HF transceiver is functioning...

🔍 Key Concepts

• MF-HF SSB voice vs. SITOR (NBDP) operation – what parts of the radio are common to both modes and what parts are unique to data modes • Filters and bandwidth – which component controls the narrower bandwidth needed for SITOR/NBDP compared to voice SSB • Internal oscillators – how an audio oscillator and a VCO are used in generating/processing SITOR tones vs. standard voice

💭 Think About

• If the radio works perfectly on SSB voice but fails only in SITOR/NBDP, which stages of the transceiver can you safely assume are probably OK? • Which option specifically affects the part of the signal path that changes between wide‑band SSB voice and narrow‑band direct‑printing (data) modes? • Ask yourself: which component, if it failed, would be most likely to affect only SITOR and not normal SSB voice operation?

✅ Before You Answer

• Identify which blocks (RF amplifiers, I.F. stages, VCO) are shared by both voice SSB and SITOR; these are less likely to be the cause if only SITOR fails. • Consider which option relates to a narrow-band filter used primarily for data modes like NBDP/SITOR rather than for standard voice. • Verify which oscillator (by frequency and function) is used to generate the SITOR tones and would be essential only when operating in NBDP mode.

An MF-HF transceiver is functioning correctly in voice mode/SSB but not in SITOR (NBDP). What is the most likely source of the problem?

The second I.F. amplifier has become defective.

The voltage controlled oscillator is defective.

The 2.8 kHz filter has become defective.

The 1615 kHz audio oscillator is not working .

🔍 Key Concepts

💭 Think About

✅ Before You Answer