121.500 MHz Civil Aviation Emergency Guard & JFK Tower
121.500 MHz is the internationally reserved aeronautical emergency frequency (Guard). Monitored 24/7 by civilian air traffic control towers, military interceptors, and commercial airliners worldwide.
121.500 MHz VHF Guard
Civil Airband (VHF) • VHF (Very High Frequency) • AM Mode
- Modulation Standard
- Amplitude Modulation (A3E AM Voice)
- Channel Grid / Bandwidth
- Dedicated International Channel (Emergency allocation)
- Transmitter Power (Typical)
- Aircraft transceivers (10–25 W) / Ground stations (50–100 W)
- Polarization
- Vertical
- Signal Propagation Mode
- Direct Space Wave / Tropospheric Line-of-Sight
- Typical Broadcast Range
- Line-of-sight: 150 to 250 nautical miles at cruise altitude (FL350)
Used for distress calls (MAYDAY / PAN-PAN), emergency locator transmitter (ELT) homing signals, military aircraft interceptions of lost civilian planes, and emergency vectoring by air traffic control.
- Standard civilian aircraft transceivers always guard 121.5 MHz on Audio Box Com 2 while cruising.
- SDR receivers situated near major international airports (e.g., JFK, Heathrow, Haneda) provide the clearest signal.
- In our interactive global SDR console, tune your receiver to 121,500 kHz in AM mode.
Frequently Asked Questions about 121.500 MHz
Who is allowed to transmit on 121.500 MHz?
Transmissions on 121.500 MHz are strictly restricted to distress, emergency situations, urgent air safety communications, and official search and rescue (SAR) operations under ICAO regulations.
Can I listen to 121.5 MHz legally online?
Yes. In the United States and most international jurisdictions, listening to unencrypted free-to-air civil airband radio transmissions via SDR (Software Defined Radio) is 100% legal.
What is the military equivalent to 121.5 MHz?
The military aeronautical emergency guard frequency is 243.000 MHz (UHF), which is the exact second harmonic of 121.5 MHz.
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