47 CFR Part 87 sets technical standards for aviation radio services, including power limits, frequency stability, and emission requirements for aircraft and ground radios. It specifies frequency allocations for different communication types, such as air-to-ground and navigation aids, to avoid interference. Emergency procedures include using the 121.5 MHz distress frequency and emergency locator transmitters (ELTs). More details on technical requirements are in subpart D of this part.

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47 CFR Part 87 outlines the technical standards for aviation radio services, including requirements for aircraft radios, ground stations, and radionavigation aids. Engineers and technicians should consider the following details:

1. Frequency Bands and Channel Allocations (47 CFR §§ 87.173, 87.187):
   Part 87 specifies frequency bands for various aviation communication purposes:

   • Air-to-Ground and Ground-to-Air Communications: Frequencies allocated for communication between aircraft and ground control (e.g., air traffic control).
   • Air-to-Air Communications: Frequencies for communication between aircraft in flight.
   • Radionavigation: Frequencies used for navigational aids like VOR, ILS, and DME.

2. Technical Standards for Transmitters (47 CFR §§ 87.131, 87.133):
   Aircraft transmitters must comply with power output limits and frequency stability requirements to avoid interference. For example, power limits for VHF radios typically range from 1 to 25 watts. Frequency stability must be maintained within specified tolerances, depending on the type of station and service.

3. Emergency Communications (47 CFR § 87.393):
   The 121.5 MHz frequency is reserved for distress and emergency locator transmitters (ELTs), used to assist in locating downed aircraft. ELTs must meet specific technical standards for signal strength and activation to ensure effective emergency responses.

4. Radionavigation Aids and Performance Standards (47 CFR § 87.475):
   Radionavigation systems, including VOR and ILS, must meet accuracy and reliability standards. Equipment used for these systems should be maintained and calibrated regularly to ensure navigation signals are accurate for aircraft approaches and enroute navigation.

5. Operational Procedures for Aviation Radios (47 CFR § 87.89):
   Operators must use standard radio procedures, such as call sign identification and compliance with communication protocols. Ground stations and aircraft are required to continuously monitor assigned frequencies to ensure prompt responses to communications.

6. Compliance with Special Provisions):
   Special rules cover services like aviation training, balloon operations, and emergency services. For example, training schools may have dedicated frequencies for instruction, while search and rescue teams have specific communication requirements.

7. Antenna Requirements and Installation Standards:
   Antennas used for aviation communication must meet Part 87 requirements for installation on aircraft and ground stations. They must ensure proper signal transmission and reception without causing harmful interference.

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