Antenna Guide
A concise introduction to the world of antennas. Whether you spotted something on a rooftop and want to know what it is, or you're just getting into the hobby — start here.
Cell Tower Antennas
The most common antennas you'll see. Tall lattice or monopole towers with rectangular panel antennas mounted at the top. Each panel covers a sector (typically 120 degrees). Modern towers carry equipment for multiple carriers and technologies — 4G LTE, 5G NR, and sometimes legacy 3G.
What to look for:
- Panel antennas — Rectangular boxes (2-6 feet tall), usually in groups of 3 covering 360 degrees
- Small cells — Compact units on utility poles or streetlights, often mistaken for surveillance equipment
- 5G mmWave — Small, square panels angled toward streets, much shorter range than traditional towers
- Remote radio heads (RRH) — Equipment boxes mounted near the antennas rather than at the base
Satellite Dishes
Parabolic reflectors that focus signals to/from satellites. Size matters — a larger dish captures more signal. You'll see everything from small home TV dishes (45-90cm) to massive earth station dishes (3-30 meters).
Common types:
- Direct-to-home TV — Small offset dishes (DirecTV, Dish Network, Sky)
- VSAT — Medium dishes (1-2m) for business internet, often on rooftops
- Earth stations — Large dishes (3m+) at teleport facilities
- Starlink — Flat phased-array panel (no traditional dish shape), the "Dishy McFlatface"
Ham Radio / Amateur Radio
Amateur radio operators ("hams") use a wide variety of antennas depending on frequency band and purpose. This is where antenna design gets creative.
Common ham antennas:
- Yagi-Uda — Directional, looks like a TV antenna with parallel elements. Used for VHF/UHF and satellite work
- Dipole — The simplest antenna: a wire cut to half wavelength, fed in the center. Often strung between trees or hung from masts
- Vertical — A single pole or whip, ground-mounted or roof-mounted. Omnidirectional pattern
- Wire antennas — Long wire, end-fed, G5RV, random wire. Cheap, effective, often invisible
- Loop antennas — Magnetic loops (small, indoor-friendly) or full-wave loops (large, outdoor)
- Beam antennas — Multi-element directional antennas on rotators for DX (long-distance) contacts
Broadcast Antennas
The big ones. FM radio and TV broadcast antennas sit atop tall towers and pump out kilowatts of power.
- FM broadcast — Circular arrays of dipoles or ring antennas near the top of towers
- TV (UHF) — Panel antennas or slotted cylinder antennas
- AM radio — The tower itself IS the antenna. Those tall, thin, guyed towers with red lights are AM broadcast towers, insulated from the ground
Microwave / Point-to-Point
Round dishes (0.3-3m) that create focused beams between two fixed points. Used by telecom companies, utilities, and broadcasters to backhaul data between towers.
- Parabolic dishes — Round, with a protective radome (cover). Usually paired — one on each end
- Flat panel — Newer designs for short-range links
- Horn antennas — Flared metal horns, used in specialized applications
Military / Radar
Military antennas range from tactical field antennas to massive phased-array radar installations.
- Phased array radar — Flat panels with hundreds/thousands of elements. Can steer the beam electronically without moving. AEGIS, THAAD, Patriot
- Rotating radar — The classic spinning dish on airports and ships (ATC, weather, military surveillance)
- SIGINT/ELINT — Large domes (radomes) hiding the actual antenna shape for secrecy. Often at listening posts
- HF whips — Long, flexible whip antennas on military vehicles
- Satellite ground terminals — Large dishes at military bases for SATCOM
Emergency / Public Safety
- Repeater sites — VHF/UHF antennas on hilltops and buildings for police, fire, EMS radio
- P25 digital — Same towers but digital trunked systems
- FirstNet — Dedicated LTE network for first responders, often co-located on existing cell towers
IoT & Smart City
- LoRa gateways — Small antennas for long-range, low-power IoT sensors
- Mesh network nodes — Small boxes on poles for municipal WiFi or smart city applications
- Smart meters — Built-in antennas in utility meters for automated reading
Quick Identification Tips
- Rectangular panels in groups of 3 = cell tower
- Round dish pointed at the sky = satellite
- Round dish pointed at the horizon = microwave point-to-point
- Parallel horizontal elements on a boom = yagi
- Tall thin tower with red lights, no visible antennas = AM broadcast (the tower is the antenna)
- Spinning dish = radar
- White dome hiding the antenna = radome (usually military, radar, or satellite)
- Small box on a utility pole = small cell or IoT gateway
Frequency Bands (Quick Reference)
| Band | Frequency | Common Use |
|---|
| HF | 3-30 MHz | Ham radio, shortwave, military |
| VHF | 30-300 MHz | FM radio, TV, ham, marine, aviation |
| UHF | 300 MHz-3 GHz | TV, cell phones (4G/5G), ham, public safety |
| SHF | 3-30 GHz | Satellite, radar, microwave links, 5G mmWave |
| EHF | 30-300 GHz | Military, research, emerging 5G/6G |
Tower Types & Structures
Understanding tower types helps you identify what kind of service an antenna installation supports before you even look at the antennas themselves.
- Lattice / Self-Supporting — Triangular or square steel framework towers, ranging from 100 to 2,000 feet. The most common type for broadcast installations. Easy to identify by their open criss-cross steel structure. Often carry multiple tenants (antennas from different carriers or broadcasters at different heights).
- Monopole — A single steel tube, typically 50 to 200 feet tall. The most common tower type for cellular installations due to their clean appearance and small ground footprint. Look for a tapered cylindrical pole with antenna arrays mounted at the top.
- Guyed Tower — A tall, thin tower held upright by guy wires anchored to the ground. Can reach over 2,000 feet, making them the tallest antenna structures. Commonly used for AM broadcast and long-range communications. Identify by the visible cables extending from the tower to anchor points on the ground.
- Rooftop Mount — Antennas installed on building rooftops, common in urban areas where standalone towers are impractical. Look for various mounting structures: tripods, non-penetrating mounts, parapet mounts, and custom steel frames. Can host cellular panels, microwave dishes, or two-way radio antennas.
- Stealth / Concealed — Towers and antennas disguised to blend into the environment. Monopines (fake pine trees) are the most famous, but you will also see fake flagpoles, church steeples, cacti, palm trees, and even clock towers. Cell carriers use these to satisfy zoning requirements and reduce visual impact. Once you know what to look for, they become easy to spot.
- COW / COLT — Cell On Wheels (COW) and Cell On Light Truck (COLT) are portable, temporary cell towers mounted on trailers or trucks. Deployed for large events (concerts, sporting events), disaster relief, or to fill coverage gaps during tower maintenance. Look for a telescoping mast on a trailer with a generator.
- Water Tower Mounts — Antennas hidden on or inside water tanks. Municipalities often lease space on water towers to carriers. The antennas may be mounted externally on the catwalk or concealed behind fiberglass panels that match the tank's appearance.
- Billboard Mounts — Cellular antennas concealed behind or within billboard structures. The billboard provides cover for the equipment, and the elevated position provides good coverage. Look for unusually thick billboard frames or panels that don't quite match the rest of the structure.
Cables, Feedlines & Waveguides
The cables and transmission lines connecting antennas to their radios are a key part of any antenna installation. Understanding them helps you identify what kind of system you are looking at.
- Coaxial Cable — The most common transmission line. RG-6 is standard for TV and home satellite. RG-8 and RG-213 are used for ham radio. LMR-400 is the go-to for commercial two-way radio. On cell towers, you will see 7/8-inch and 1-5/8-inch hardline (rigid coax with a corrugated outer conductor) running from the equipment shelter to the antenna arrays.
- Waveguide — Rectangular or circular hollow metal tubes used for microwave frequencies. Visible on large dish antenna feeds and high-power radar installations. They carry RF energy with very low loss at frequencies where coax becomes impractical (typically above 10 GHz).
- Fiber Optic — Increasingly used for the connection between tower-mounted radio equipment and the base station shelter (fronthaul). Protocols like CPRI and eCPRI carry digitized radio signals over fiber. Look for hybrid cables that bundle fiber with power conductors running up the tower.
- Jumper Cables — Short, flexible coaxial cables that connect antennas to tower-mounted amplifiers or remote radio heads. Usually 1/2-inch or 5/8-inch diameter with weatherproofed connectors. You will see them as the short cable runs at the very top of cell towers connecting each antenna to its nearby equipment box.
- How to identify — Coax has round connectors (N-type for commercial, SMA for small equipment, 7-16 DIN for cell towers). Hardline is rigid with flanged or EIA connectors. Waveguide is rectangular and unmistakable. Fiber is thin and often orange or yellow. On towers, cables are typically bundled and run along cable ladders or ice bridges from the shelter to the antennas.
Antenna Height Estimation
Knowing how tall a tower or antenna is helps with identification and understanding its coverage area. Here are practical methods for estimating height in the field.
- Comparison Method — Use objects of known height as reference points. One building story is approximately 10 feet. A standard utility pole is about 35 feet. A person is roughly 6 feet. Count how many reference units fit into the tower height and multiply.
- Shadow Method — On a sunny day, measure the shadow length of the tower and compare it to the shadow of an object with a known height (like a pole or a person). The ratio of shadow lengths equals the ratio of actual heights. Works best when the sun is at a moderate angle.
- Clinometer / Inclinometer Apps — Smartphone apps that use the phone's sensors to measure the angle to the top of a tower. Stand a known distance from the base, measure the angle, and the app calculates the height using trigonometry. Many are free and surprisingly accurate.
- FCC ASR Database — If the tower is registered, its exact height is available in the FCC Antenna Structure Registration database. Search by location or registration number at the FCC website. Towers over 200 feet or near airports are required to be registered.
- Google Earth — The 3D view in Google Earth can help estimate building and tower heights by comparing them to surrounding structures. Some areas have detailed 3D models where you can use the ruler tool to measure approximate heights.
Propagation Basics
How radio waves travel from antenna to receiver determines everything about antenna placement, height, and design. Understanding propagation basics makes antenna spotting much more meaningful.
- Line of Sight (LOS) — At higher frequencies (above ~30 MHz), radio waves travel in essentially straight lines. If you can see the antenna, you can probably receive its signal. This is why cell towers and microwave dishes are placed on high points.
- Fresnel Zone — The ellipsoidal area around the direct line-of-sight path between two antennas that must be clear of obstructions for good signal quality. Even if you have visual line of sight, a building or hill intruding into the Fresnel zone can degrade the signal. This is why microwave links are placed well above surrounding obstacles.
- Why Height Matters — A higher antenna sees a farther radio horizon, which means better coverage. The approximate formula is: distance in miles equals 1.23 times the square root of the antenna height in feet. So a 100-foot antenna can reach about 12.3 miles to the horizon, while a 400-foot antenna reaches about 24.6 miles.
- Frequency vs Penetration — Lower frequencies (like 700 MHz LTE or AM radio) penetrate buildings and foliage much better than higher frequencies. Higher frequencies (like 5G mmWave at 28-39 GHz) carry far more data but are blocked by walls, glass, and even rain. This is why carriers deploy a mix of frequencies.
- Multipath — Radio signals bouncing off buildings, vehicles, and terrain arrive at the receiver via multiple paths with different delays, causing interference and fading. Modern MIMO antenna systems (the reason cell panels have so many elements) actually exploit multipath to increase data throughput by sending different data streams on each path.
FCC Regulations & Licensing
Antennas operate under a framework of regulations that determine who can transmit, on what frequencies, and at what power levels. Knowing the basics helps you understand what you are looking at.
- Part 15 — Unlicensed Devices — Covers WiFi routers, Bluetooth devices, garage door openers, baby monitors, and other low-power consumer electronics. No license required, but very strict power limits. This is why your WiFi router cannot reach very far.
- Part 97 — Amateur (Ham) Radio — Requires passing a license exam. Three license classes: Technician (entry level, VHF/UHF privileges), General (adds most HF bands), and Extra (full privileges on all bands). Hams can build their own equipment and use significant power (up to 1,500 watts).
- Part 22/24/27 — Commercial Cellular — The frequencies used by cell carriers (AT&T, Verizon, T-Mobile, etc.) are licensed through FCC spectrum auctions. Carriers pay billions for exclusive rights to use specific frequency bands in specific geographic areas.
- ASR Requirements — Antenna Structure Registration is required for any tower over 200 feet tall or any tower near an airport that could affect air navigation. Registered towers must be painted and lit according to FAA specifications (those red lights and orange-white paint schemes).
- RF Exposure Limits — The FCC sets limits on how much RF energy people can be exposed to, detailed in OET Bulletin 65. Cell towers are designed to comply with these limits. The areas directly in front of high-power antennas at close range (within a few feet) can exceed exposure limits, which is why tower workers follow strict safety protocols.
- Tower Climbing Safety — Never climb antenna towers without proper authorization, training, and fall protection equipment. Tower climbing is one of the most dangerous jobs in America. Unauthorized climbing is trespassing and extremely dangerous due to RF exposure, electrical hazards, and fall risk.
Accessories & Equipment
Beyond the antennas themselves, a variety of supporting equipment makes antenna systems work. Spotting these accessories tells you more about the installation.
- Rotators — Motorized mounts that aim directional antennas (like yagis and beams). Common in ham radio for working stations in different directions, and used for TV antennas in fringe reception areas. Look for a motor housing where the antenna boom meets the mast.
- Antenna Analyzers / SWR Meters — Instruments that measure antenna performance including return loss, impedance, and standing wave ratio (SWR). Essential tools for anyone installing or tuning antennas. Modern analyzers display a graph of antenna performance across a range of frequencies.
- Lightning Arrestors — Devices installed in the feedline between the antenna and the radio to protect equipment from lightning-induced surges and static buildup. Look for small cylindrical or rectangular inline devices on the cable near where it enters a building.
- Duplexers / Diplexers — Allow multiple frequencies or services to share a single antenna. A duplexer lets a repeater transmit and receive on the same antenna simultaneously. A diplexer combines two different frequency bands (like VHF and UHF) onto one feedline.
- Tower-Mounted Amplifiers (TMAs) — Low-noise amplifiers installed right next to the antenna to boost weak received signals before they travel down the long cable run to the base station. Common on cell towers. Look for small weatherproof boxes mounted very close to the panel antennas.
- Remote Radio Heads (RRH/RRU) — The equipment boxes you see mounted next to cell tower antennas. They contain the radio electronics (transmitter, receiver, digital processing) and are connected to the baseband unit in the ground shelter via fiber. Moving the radio close to the antenna dramatically reduces signal loss.
- Surge Protectors & Grounding — Essential for any antenna installation. Proper grounding includes a ground rod at the antenna base, ground wire running alongside the feedline, and a grounding block where cables enter the building. On towers, look for thick copper ground straps running from the equipment to the tower structure.