Transmitters & Receivers in DepthRadio Telephony — DGCA CPL practice questions
Question 1 of 17
Aviation VHF voice communication operates in which mode?
All 17 questions — Transmitters & Receivers in Depth
Radio Telephony · DGCA CPL. The correct option is marked on each.
Q1. Aviation VHF voice communication operates in which mode?
- A.Simplex✓
- B.Duplex
- C.Full-duplex
- D.Broadcast only
Why: A single shared frequency, one transmitter at a time — simplex (PTT).
Q2. ATIS is an example of:
- A.Duplex
- B.Simplex broadcast (listen only)✓
- C.Half-duplex
- D.Two-way simplex
Why: ATIS is a one-way broadcast; aircraft only listen.
Q3. Duplex operation uses:
- A.One frequency, one at a time
- B.Two frequencies, allowing simultaneous transmit and receive✓
- C.No frequency
- D.Only HF
Why: Duplex uses two frequencies so both ends can talk at once.
Q4. A "stuck microphone" on a simplex frequency:
- A.Improves the signal
- B.Blocks the whole frequency for everyone✓
- C.Only affects that aircraft
- D.Changes the frequency
Why: locks the whole frequency for everyone. A held/stuck PTT transmits continuously, blocking the shared channel; the offender can't hear it.
Q5. The correct PTT sequence is:
- A.Speak, press, release, listen
- B.Listen, press & pause, speak, release fully✓
- C.Press and hold throughout the exchange
- D.Press and speak instantly
Why: Listen out, press and pause, speak clearly, then release fully to hear the reply.
Q6. A noise-cancelling microphone:
- A.Increases transmitter power
- B.Rejects steady cockpit noise so mainly speech is transmitted✓
- C.Tunes the radio
- D.Replaces the antenna
Why: It cancels the steady ambient roar, transmitting clearer speech.
Q7. The intercom (interphone) is used to:
- A.Transmit to ATC
- B.Let the crew talk to each other without transmitting on the radio✓
- C.Broadcast ATIS
- D.Tune the navigation receiver
Why: Intercom is internal; it does not go out on the radio.
Q8. The function of squelch is to:
- A.Increase transmitter power
- B.Mute background noise until a signal is received✓
- C.Change frequency automatically
- D.Keep audio level constant
Why: Squelch silences the hiss when no signal is present; keeping level constant is AVC's job.
Q9. AVC (automatic volume control) acts to:
- A.Mute weak signals
- B.Hold the received audio at a steady level despite signal variation✓
- C.Boost transmit power
- D.Select the frequency
Why: AVC/AGC keeps the wanted signal's level steady as strength changes.
Q10. Setting the squelch too tight will:
- A.Increase range
- B.Mute weak (distant) signals so they are missed✓
- C.Boost the audio
- D.Have no effect
Why: Too-tight squelch keeps the audio closed to weak but wanted signals.
Q11. The VHF communication antenna is mounted:
- A.Horizontally
- B.Vertically, to match the vertically-polarized VHF signal✓
- C.Inside the cabin
- D.At 45°
Why: Aviation VHF is vertically polarized, so the blade is vertical.
Q12. A poorly matched antenna causes:
- A.More radiated power
- B.Power reflected back (high VSWR), wasted and risking the transmitter✓
- C.A lower frequency
- D.Better range
Why: A mismatch reflects power (high VSWR) instead of radiating it.
Q13. HF aerials need a coupler/tuner because:
- A.HF is line-of-sight
- B.HF wavelengths are too long for a full-size aerial on an airframe✓
- C.HF uses AM
- D.HF needs no antenna
Why: A 3 MHz quarter-wave is 25 m; a coupler makes a short aerial behave as resonant.
Q14. ACARS is best described as:
- A.A navigation aid
- B.A digital datalink for short text messages between aircraft and ground✓
- C.An emergency beacon
- D.A type of antenna
Why: digital datalink for short text messages between aircraft and ground. ACARS carries short text messages, reducing voice workload.
Q15. On total radio failure, the transponder code to select is:
- A.7500
- B.7600✓
- C.7700
- D.2000
Why: 7600 indicates radio/communications failure (7500 hijack, 7700 emergency).
Q16. Before declaring a radio failure you should first check:
- A.The weather
- B.Frequency, volume, squelch, audio-panel selectors, PTT/plug and power✓
- C.The transponder code
- D.The fuel
Why: Work the quick checks; many "failures" are a wrong frequency, tight squelch or wrong selector.
Q17. A limitation of VHF radiotelephony is:
- A.Unlimited range
- B.Range restricted to line-of-sight✓
- C.It needs no frequency
- D.It cannot be misheard
Why: VHF is line-of-sight; range grows with altitude but is horizon-limited.