What is it?

The PABM1 Passive Air Band Monitor is a non-interfering AM receiver for the radio band used for air traffic control. It receives all nearby transmissions within the band used for voice communications between civilian aircraft and air traffic control centers.

FAA (Federal Aviation Administration) regulations generally forbid the use of receivers onboard commercial aircraft because a normal receiver's local oscillator can radiate signals that could interfere with aircraft communication and navigation systems. However, the PABM1 Passive Air Band Monitor directly detects nearby AM signals in the 118 to 137 MHz VHF (very-high-frequency) aircraft voice band without the use of internal oscillators, and thus cannot interfere with aircraft communications and navigation equipment.

This monitor operates on one standard 9V battery (not included). A pair of stereo headphones or earphones are required (not included).

WARNING: It is completely legal in the US to listen to Air Traffic Control (ATC) communications. However, listening to airband frequencies without a license is an offence in some countries (e.g., the UK). Please check local laws for the legality of possessing and using the PABM1.

Although the PABM1 cannot interfere with an aircraft's communication and navigation systems, always ask permission from the flight crew before using it onboard an aircraft.

A complete manual is available under "Specs and Docs" section.

Why did you make it?

To keep informed about what's REALLY going on while traveling.

What makes it special?

In 1961, the FCC (Federal Communications Commission) prohibited the operation of FM receivers onboard aircraft since they were determined to interfere with the operation of navigation and communication systems. The FAA (Federal Aviation Administration) subsequently determined that other personal electronic devices could be potentially hazardous to aircraft systems if operated aboard aircraft and prohibited their use.

The reason normal receivers have the potential of interfering with aircraft communications is that they internally produce radio signals as part of the receiving circuitry. Standard receivers have one or more oscillators that produce radio signals used by the radio to tune to a specific frequency. Signals from these oscillators that escape the receiver may interfere with communication and navigation signals.

In contrast, the PABM1 Passive Air Band Monitor does not contain any oscillators or other radio-frequency sources that may radiate interfering signals. Signals picked up by the antenna are filtered within the airband and then directly demodulated to produce audio. The reason why this is not done in normal receivers is that direct demodulation makes it very difficult to tune to a specific frequency, allowing all signals within a band to come through simultaneously. In the case of our airband monitor, this is an advantage since no knowledge of the frequency used for air traffic control is necessary, thus requiring no tuning.