Very High Frequency (VHF) radio is the backbone of aviation communication in the United States and around the world. Whether you are a student pilot learning to talk to a controller or a Part 107 remote pilot coordinating with manned aircraft operations, understanding how VHF frequencies are organized — and why each band slice is used the way it is — is essential knowledge. The FAA knowledge test expects you to recognize specific frequency ranges, identify the purposes of key channels, and understand the rules governing their use.
While a drone pilot does not personally transmit on aviation radio frequencies during most operations, Part 107 rules require remote pilots to understand airspace, manned aircraft operations, and the communication infrastructure that keeps the National Airspace System (NAS) safe. If you ever fly near a towered airport, coordinate with ATC for a waiver, or simply need to monitor an active frequency before launching, this knowledge becomes immediately practical.
The VHF Aviation Band: 118.000 to 136.975 MHz
Aviation uses a dedicated slice of the VHF spectrum from 118.000 MHz to 136.975 MHz. This range was internationally standardized through the International Civil Aviation Organization (ICAO) and is protected for aeronautical communication worldwide. VHF signals in this range travel in essentially straight lines (line-of-sight propagation), which means range is limited by the curvature of the earth and terrain, but interference from distant stations is also minimized — a practical benefit in a system where dozens of airports may be geographically close.
Within that 118–137 MHz band, the FAA and ICAO organize frequencies into specific functional sub-bands. Each block of frequencies is assigned a general purpose, though individual frequencies within a block are assigned to specific facilities by the FAA's Spectrum Management office. Understanding the functional blocks helps you quickly associate a frequency you hear with its purpose.
Key Sub-Band Assignments and How They Work
Emergency Frequency: 121.500 MHz
121.500 MHz is the international aeronautical emergency frequency, universally known as "Guard." All aircraft equipped with VHF radios are strongly encouraged — and military aircraft are required — to monitor 121.500 MHz whenever a second radio is available. This frequency is used for distress calls (MAYDAY), urgency calls (PAN-PAN), and direction-finding by search-and-rescue services. Emergency Locator Transmitters (ELTs) in older aircraft also transmitted on 121.500 MHz, though modern ELTs transmit on 406 MHz for satellite detection. As a remote pilot, you should know that 121.500 MHz is never used for routine communication — it is strictly reserved for emergencies.
Ground Control: Typically 121.600–121.900 MHz
Ground control frequencies generally fall in the 121.600–121.900 MHz range. Ground controllers use these frequencies to direct aircraft movement on taxiways and the airport surface when not on an active runway. Common ground frequencies you will see published in the Chart Supplement include 121.700, 121.800, and 121.900 MHz. A pilot transitions from ground control to the tower frequency when cleared onto an active runway or for takeoff.
Clearance Delivery and Pre-Taxi: Lower 120s
At larger airports, clearance delivery frequencies are typically assigned in the lower portion of the 120–122 MHz range. Pilots call clearance delivery before taxiing to receive their IFR route clearance or any special instructions. This keeps the ground and tower frequencies from being cluttered with lengthy readbacks of complex clearances.
Tower (Local Control): 118.000–135.975 MHz
Tower frequencies — used by the local controller who manages aircraft on the runway and in the immediate vicinity of the airport — are distributed broadly across the entire aviation band, but many are assigned in the 118–127 MHz portion. The specific frequency for each airport's tower is published in the FAA Chart Supplement (formerly the Airport/Facility Directory), on sectional charts, and in the Aeronautical Information Manual (AIM). If you are operating a drone near a towered airport under a LAANC authorization or ATC waiver, you should know the tower frequency so you can monitor it for situational awareness about manned traffic.
CTAF — Common Traffic Advisory Frequency
At non-towered airports (and at towered airports during hours when the tower is closed), pilots use a Common Traffic Advisory Frequency (CTAF) to self-announce their intentions and position. The CTAF is printed on sectional charts with a magenta letter C next to the frequency. CTAF frequencies are often in the 122.700–122.975 MHz range, but they can also be a UNICOM, MULTICOM, or even an FSS frequency depending on the airport. 122.800 MHz is the most widely used UNICOM frequency for non-towered airports in the contiguous United States. 122.900 MHz is commonly used as a MULTICOM frequency for activities conducted away from an established airport, such as aerial application or balloon operations.
MULTICOM: 122.900 MHz
122.900 MHz serves as the MULTICOM frequency — used for air-to-air communications among aircraft operating in areas where there is no tower, FSS, or UNICOM service. Crop dusters, pipeline patrol aircraft, and other special-use operations often use this channel to communicate with ground crews or other aircraft in an area without airport services.
Flight Service Stations (FSS): 122.200 MHz and Others
Flight Service Stations provide preflight briefings, weather updates, NOTAMs, and pilot reports. While FSS services are mostly accessed by telephone today (1-800-WX-BRIEF), pilots can still reach FSS by radio. 122.200 MHz is the common en route FSS frequency. FSS stations also transmit weather on navigational aid frequencies while listening on 122.200 MHz — a technique called "transmit on the VOR, listen on 122.2."
ATIS: Typically 118.000–135.975 MHz (Locally Assigned)
The Automatic Terminal Information Service (ATIS) is a recorded broadcast of current weather, active runway, and NOTAM information at busier airports. ATIS frequencies are locally assigned within the main aviation band and are printed on sectional charts and in the Chart Supplement. Pilots (and savvy remote pilots planning operations near busy airspace) should listen to ATIS before any coordination call, because controllers expect you to have the current "information identifier" (a letter of the alphabet that cycles with each update).
Why It Matters for Part 107 Remote Pilots
Part 107 remote pilots do not hold an FAA airman's radio license and are not required to transmit on aviation frequencies. However, the FAA expects remote pilots to understand the communication environment around them. If you fly near a towered airport under a LAANC authorization or a Part 107 waiver that includes ATC communication requirements, you may need to monitor a tower or ground frequency. More broadly, understanding which frequencies to listen to gives you genuine situational awareness about manned aircraft activity in your area, improving safety for everyone sharing the airspace.
Additionally, the FAA knowledge test for the Remote Pilot Certificate includes questions about radio communication procedures, frequency usage, and airspace operations. Misidentifying the emergency frequency, confusing CTAF with UNICOM, or not knowing that 121.500 MHz is Guard can cost you exam points.
Key Numbers and Rules
- 118.000–136.975 MHz — The full VHF aviation communication band.
- 121.500 MHz — International emergency (Guard) frequency; never used for routine calls.
- 121.600–121.900 MHz — Typical range for airport ground control frequencies.
- 122.200 MHz — Common en route Flight Service Station (FSS) frequency.
- 122.700–122.975 MHz — Typical range for CTAF/UNICOM frequencies at non-towered airports.
- 122.800 MHz — Standard UNICOM frequency for non-towered airports.
- 122.900 MHz — MULTICOM; used for airborne operations away from established airports.
- 123.500 MHz — UNICOM for heliports and some gliderport and balloon operations; check the Chart Supplement for confirmation.
- Tower and ATIS frequencies are locally assigned throughout 118–136 MHz and must be looked up in the Chart Supplement or sectional chart for each specific airport.
Common Test Traps
- Confusing 121.500 with a routine frequency. The exam sometimes describes a scenario where a pilot needs to reach ATC or FSS and lists 121.500 MHz as an option. It is emergency-only — selecting it for routine calls is always wrong.
- CTAF vs. UNICOM. CTAF is a concept (the designated frequency for self-announcing at a non-towered field); UNICOM is a specific type of service. They often share the same frequency (commonly 122.800 MHz), but they are not the same thing. When a tower is closed, the tower frequency itself may serve as the CTAF.
- Assuming ground control is always on 121.9. Ground frequencies vary by airport. Always verify with published sources; 121.900 is common but not universal.
- Thinking all VHF aviation is in the 121–123 MHz range. Tower and approach frequencies extend across the whole 118–137 MHz band. Many students forget that assigned frequencies like 132.750 or 135.100 are perfectly valid aviation tower or approach channels.
- Forgetting that remote pilots need this knowledge. Some Part 107 candidates assume radio procedures are irrelevant to drone flying. The FAA Airman Certification Standards for Remote Pilots explicitly include radio communication knowledge, and exam questions test it directly.