What is the correct frequency shift and...

What is the correct frequency shift and...

Question 1 of 27070mcvFgiftoNV4nSe3sgN5

What is the correct frequency shift and sub-carrier for VHF-DSC?

Question 1 of 27070

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Q

What is the correct frequency shift and sub-carrier for VHF-DSC?

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🔍 Key Concepts

• Digital Selective Calling (DSC) modulation on VHF uses audio tones, not the RF carrier frequency itself • The frequency shift is the difference between the two audio tones used for the FSK (frequency shift keying) signal • The sub‑carrier frequency is the midpoint between the two DSC audio tones

💭 Think About

• First recall the two specific audio tone frequencies used for VHF‑DSC; from those, you can calculate the shift and the midpoint • Ask yourself: if the lower tone is X Hz and the higher tone is Y Hz, what is Y − X, and what is (X + Y) / 2? • Compare the calculated shift and midpoint to each answer choice and see which pair exactly matches known VHF‑DSC specs

✅ Before You Answer

• Be sure you are using the audio tone pair for VHF‑DSC (156.525 MHz channel 70), not MF/HF DSC values • Double‑check your arithmetic for the shift (difference between tones) and sub‑carrier (average of the two tones) • Confirm that the option you choose matches both the correct frequency shift and the correct sub‑carrier; eliminate any that only match one of them