During transmission on VHF 1, which compass is not valid?

During transmission on VHF 1, which compass is not valid?

• A. Standby Magnetic Compass
• B. Primary Direction Finder
• C. Horizontal Situation Indicator
• D. VOR

Answer: (A)

When you’re transmitting on VHF, the cockpit is filled with RF energy that can disturb sensitive instruments. The Standby Magnetic Compass is a simple magnet-based instrument with little shielding, so its reading can be distorted by the transmitter’s electromagnetic field. For that reason, it isn’t considered reliable or valid for navigation during a VHF 1 transmission. The other instruments—Primary Direction Finder, Horizontal Situation Indicator, and VOR—rely on electronic navigation signals or separate receivers and are designed to remain usable even while you’re transmitting, so they remain valid.

When you’re transmitting on VHF, the cockpit is filled with RF energy that can disturb sensitive instruments. The Standby Magnetic Compass is a simple magnet-based instrument with little shielding, so its reading can be distorted by the transmitter’s electromagnetic field. For that reason, it isn’t considered reliable or valid for navigation during a VHF 1 transmission. The other instruments—Primary Direction Finder, Horizontal Situation Indicator, and VOR—rely on electronic navigation signals or separate receivers and are designed to remain usable even while you’re transmitting, so they remain valid.