You are able to hear signals in the...

🔍 Key Concepts

• Difference between voice/SSB reception and SITOR/NBDP (narrow‑band direct printing) reception on HF • What role the I.F. filter bandwidth plays when switching from voice to narrow‑band data modes • Which receiver stages (R.F. amp, I.F. filter, BFO, PLL) are common to all modes vs. specific to digital modes

💭 Think About

• If you can clearly hear SSB voice signals but the SITOR mode will not decode or print, which parts of the receiver are clearly working? • Which of the listed circuits would affect only the narrow‑band data mode and not normal SSB voice reception? • Think about what extra frequency shaping or filtering is required to reliably copy a 170–200 Hz shift narrow‑band teletype signal compared to plain voice

✅ Before You Answer

• Confirm which circuit failure would also prevent reception of any signals (voice and data) and eliminate those choices. • Identify which component is specifically responsible for the narrow 500 Hz bandwidth used for NBDP/SITOR modes. • Make sure the option you pick explains why voice works fine but SITOR fails—it should affect only the data mode path, not the basic RF/IF chain.

You are able to hear signals in the voice/SSB mode but not in the SITOR (NBDP) mode. What is the most likely cause?

The phase locked loop circuit has failed.

The 500 Hz I.F. filter has become defective .

The R.F. amplifier has failed.

The B.F.O. circuit has failed.

🔍 Key Concepts

💭 Think About

✅ Before You Answer