TRUE/FALSE: Operating the HF radio in high power may result in fluctuations in RADALT indications.

TRUE/FALSE: Operating the HF radio in high power may result in fluctuations in RADALT indications.

• A. True
• B. False
• C. Not applicable
• D. Not specified

Answer: (A)

High-power operation of the HF radio can generate RF energy that may couple into other avionics, including the radar altimeter. The radar altimeter relies on a sensitive microwave receiver to measure the time it takes for a radio pulse to return from the ground. When strong RF energy from the HF transmitter leaks into the aircraft’s electrical system or into the altimeter’s receiver path, it can appear as noise or spurious signals, causing the displayed altitude to fluctuate or jitter. In practice, if you observe unstable RADALT indications while transmitting at high HF power, reduce HF power, adjust shielding or filtering, or temporarily turn off HF as required by procedures. The possibility of EMI from high-power HF transmissions explains why the RADALT can fluctuate in this scenario, whereas at lower power or with proper shielding the effect is minimized.

High-power operation of the HF radio can generate RF energy that may couple into other avionics, including the radar altimeter. The radar altimeter relies on a sensitive microwave receiver to measure the time it takes for a radio pulse to return from the ground. When strong RF energy from the HF transmitter leaks into the aircraft’s electrical system or into the altimeter’s receiver path, it can appear as noise or spurious signals, causing the displayed altitude to fluctuate or jitter. In practice, if you observe unstable RADALT indications while transmitting at high HF power, reduce HF power, adjust shielding or filtering, or temporarily turn off HF as required by procedures. The possibility of EMI from high-power HF transmissions explains why the RADALT can fluctuate in this scenario, whereas at lower power or with proper shielding the effect is minimized.