Broadcast Intelligence
Enter a market area and click Scan to analyze AM/FM/TV broadcast environment.
WHO BUYS THIS: Film/TV production teams, broadcast engineers, tower companies, real estate developers (RF interference), telecom attorneys.
U.S. Broadcast Band Allocations
The AM broadcast band spans 535 to 1705 kHz with 10 kHz channel spacing (107 channels). AM stations use amplitude modulation and are classified by the FCC into four classes:
| Class | Power | Coverage | Notes |
|---|---|---|---|
| Class A | 10–50 kW | Primary: wide area | Clear channel, dominant signal. Protected skywave. |
| Class B | 0.25–50 kW | Regional | Secondary service area. Many share frequencies. |
| Class C | 0.25–1 kW | Local | Daytime power; many must reduce at night or sign off. |
| Class D | 0.25–50 kW | Daytime only | No nighttime authorization. Operates sunrise to sunset. |
Key fact: AM signals travel much farther at night due to ionospheric skywave reflection off the F2 layer. This is why many Class C/D stations must reduce power or cease operations after sunset — to protect distant clear-channel stations.
88.0 to 108.0 MHz with 200 kHz channel spacing (100 channels). FM uses frequency modulation, providing better audio fidelity and noise immunity than AM.
| Class | Max ERP | Max HAAT | Coverage Radius |
|---|---|---|---|
| Class A | 6 kW | 100 m | ~28 km |
| Class B1 | 25 kW | 100 m | ~44 km |
| Class B | 50 kW | 150 m | ~65 km |
| Class C3 | 25 kW | 100 m | ~50 km |
| Class C2 | 50 kW | 150 m | ~65 km |
| Class C1 | 100 kW | 299 m | ~92 km |
| Class C | 100 kW | 600 m | ~92 km |
LPFM: Low-Power FM stations (LP100 at 100W, LP10 at 10W) serve hyperlocal communities. Created by FCC in 2000.
FM capture effect: A stronger FM signal suppresses a weaker co-channel signal by only ~1 dB advantage. This is why FM doesn’t experience the same co-channel interference issues as AM.
| Band | Range | Channels | Notes |
|---|---|---|---|
| VHF-Lo | 54–88 MHz | 2–6 | Long range, large antennas. Gap at 72–76 MHz (Ch 5-6 gap). |
| VHF-Hi | 174–216 MHz | 7–13 | Good propagation, moderate antenna size. |
| UHF | 470–698 MHz | 14–51 | Post-repack range. Channels 38–51 cleared for wireless (600 MHz auction). |
Each TV channel occupies 6 MHz bandwidth (ATSC standard). ATSC 1.0 uses 8VSB modulation; ATSC 3.0 (NextGen TV) uses OFDM for mobile reception and improved compression.
Digital cliff effect: Unlike analog TV which degrades gracefully, digital TV either works perfectly or fails completely. There is no gradual degradation — signal drops below threshold and the picture disappears entirely.
FCC Broadcast Regulatory Reference
47 CFR Part 73 governs all broadcast radio and television stations in the United States. Key subparts:
Subpart B — FM Broadcast Stations: channel assignments, power limits, antenna requirements, coverage contours.
Subpart A — AM Broadcast Stations: daytime/nighttime power, directional antenna requirements, skywave protection.
Subpart E — Television Broadcast Stations: channel allocations, interference protection, ATSC standards.
Subpart G — Low Power FM (LPFM): 10W and 100W noncommercial educational stations.
47 CFR Part 74 covers broadcast auxiliary operations that support main broadcast stations:
STL (Studio-Transmitter Link): 944–952 MHz microwave links carrying audio/video from studio to transmitter site. Interference to STL can take a station off the air.
ICR (Intercity Relay): 6875–7125 MHz point-to-point microwave connecting broadcast facilities across cities.
RPU (Remote Pickup Unit): 450–455 MHz frequencies used for live field reporting (ENG — Electronic News Gathering).
TV Translators: Low-power retransmitters that extend TV coverage into terrain-shadowed areas. Operate on different channels than the parent station.
OET Bulletin 65 establishes RF exposure evaluation criteria. Broadcast transmitters, especially AM and high-power FM/TV, can exceed FCC Maximum Permissible Exposure (MPE) limits near the antenna.
AM stations with directional arrays require special attention because the entire tower structure is the antenna. Ground-level fields can exceed MPE within the tower compound.
FM and TV stations mounted on tall towers typically have safe ground-level exposure but may present hazards to tower climbers and nearby rooftop locations.
🎬 Film & TV Production RF Command Center
Broadcast RF Training
AM Radio
Amplitude Modulation. 535–1705 kHz. Longer range especially at night via skywave. Lower audio quality than FM. Used for news, talk, sports. The entire tower IS the antenna.
FM Radio
Frequency Modulation. 88–108 MHz. Better audio fidelity, stereo capability. Line-of-sight propagation (no skywave). Coverage determined by ERP and HAAT. Used for music, NPR, community radio.
Television
Digital TV (ATSC). VHF and UHF bands. 6 MHz channel bandwidth. High power stations (up to 1 MW ERP for UHF). Coverage contours defined by FCC Grade B field strength.
Broadcast Auxiliary
STL, ICR, RPU, translators. These support main stations. STLs carry the programming from studio to transmitter. RPUs enable live remote broadcasts. Translators extend coverage into shadowed areas.
Callsign: Station identifier (e.g., WSB, WABE). West of the Mississippi starts with K; east starts with W.
Frequency: The assigned operating frequency in MHz (FM) or kHz (AM).
ERP (Effective Radiated Power): The actual power radiated after accounting for antenna gain and line loss. Determines coverage radius.
HAAT (Height Above Average Terrain): More important than physical tower height. Calculated by averaging terrain elevation along 8 radials from 3 to 16 km. A hilltop site with 30m tower can have higher HAAT than a flatland site with 300m tower.
Contour: The geographic boundary where signal strength meets a defined threshold. Grade A (strong) and Grade B (minimum usable) contours are specified in the license.
ERP vs. TPO: TPO (Transmitter Power Output) is what leaves the transmitter. ERP = TPO × antenna gain ÷ line loss. A 10 kW TPO with 6 dBd antenna gain and 1 dB line loss yields ~32 kW ERP.
HAAT determines coverage: Doubling HAAT increases coverage radius by ~41% (square root relationship). This is why broadcasters fight for mountaintop sites.
FM capture effect: An FM receiver locks onto the stronger of two co-channel signals with only ~1 dB advantage. This makes FM naturally resistant to co-channel interference.
AM ground conductivity: AM daytime coverage depends heavily on ground conductivity. Saltwater coasts provide the best AM propagation; rocky/sandy soil the worst.