Putting up antennas

An antenna only works once it is up, and it has to stay up through wind, ice and storms without hurting anyone. This guide covers the practical side: siting, hanging wire antennas, masts and verticals, the coax run into the house, and lightning protection. The antennas guide explains how the antennas themselves work, the connectors and cables guide covers coax and connectors, and the electrical and antenna safety guide covers shock, batteries and tower climbing in more depth.

Plan around power lines first

Choose the spot before you buy anything. The minimum the exams teach is enough distance that if the antenna falls, no part of it can come within 10 feet of the power wires (Technician pool, T0B06). The ARRL goes further: towers and masts should be installed twice the height of the installation away from power lines, every wire should be treated as energized, including cable TV and telephone lines, and metal ladders should be avoided anywhere near utility lines (ARRL, Antenna and Tower Safety). Never attach an antenna to a utility pole, where it could contact high-voltage lines (Technician pool, T0B09).

Permits, HOAs and airports

Permits and insurance. The ARRL notes that your town or city will probably require a building permit for a tower or antenna, and that a tower installation may increase your liability, so check that your insurance covers it (ARRL, Antenna and Tower Safety).

State and local rules (PRB-1). FCC rules let a station antenna structure be built “at heights and dimensions sufficient to accommodate amateur service communications.” State and local regulation must not preclude amateur communications; it “must reasonably accommodate such communications and must constitute the minimum practicable regulation to accomplish the state or local authority’s legitimate purpose” (47 CFR 97.15(b); General pool, G1B06; Extra pool, E1B07 and E1B11). This is the PRB-1 policy.

Deed restrictions and HOAs. PRB-1 covers state and local government only. The FCC decided not to extend it to private covenants, conditions and restrictions (CC&Rs) in deeds and homeowner association rules, and its 2012 report to Congress notes that later requests to change that were denied (FCC, DA 12-1342). The FCC rule that limits restrictions on TV antennas and satellite dishes does not help either: it covers antennas for television, satellite and certain commercial fixed wireless services, and it says that “fixed wireless signals” do not include amateur radio (47 CFR 1.4000). The ARRL tracks bills in Congress that would change this (ARRL). Read your deed and HOA rules before you build.

Near airports. An antenna structure more than 200 feet above ground, or one near an airport, may require notifying the Federal Aviation Administration and registering with the FCC under Part 17 (47 CFR 97.15(a); General pool, G1B01; Extra pool, E1B06). Near an airport the trigger is an imaginary surface rising from the nearest runway or landing area, and its slope depends on the airport:

• 1 foot up for every 100 feet out, to 20,000 feet, for an airport whose longest runway is more than 3,200 feet.
• 1 foot up for every 50 feet out, to 10,000 feet, for an airport whose longest runway is 3,200 feet or less.
• 1 foot up for every 25 feet out, to 5,000 feet, for a heliport.

The airports that count are public use airports in the FAA’s published directories, military airports and airports under construction for public use, airports operated by a federal agency or the Department of Defense, and any airport or heliport with an FAA-approved instrument approach procedure. For example, on ground level with the runway, a 45 foot mast 2,000 feet from a small airport’s runway exceeds the 50 to 1 surface (40 feet at that distance). An antenna structure 20 feet tall or less needs no notice, unless it would raise the height of another antenna structure (47 CFR 17.7; 14 CFR 77.9). The FAA’s OE/AAA site is where notices are filed.

RF exposure. Every station must either qualify for an exemption from a routine RF exposure evaluation or be evaluated (47 CFR 1.1307(b)), and the distance from the antenna to people matters for both. See the RF exposure guide and the RF exposure evaluator.

Location. Trees, power lines and other antennas near an antenna reduce its efficiency, so mount it as high and in the clear as you can (Cushcraft).

Hanging wire antennas in trees

For hams with trees to use as supports, the ARRL calls the dipole the most popular HF antenna (ARRL). The antennas guide shows how to size one.

Getting a line over a branch. Hams use slingshots, bows and arrows and air-powered launchers to put a light line over a high branch, then use it to pull successively larger twine and rope into place (QST, October 2019). Before you launch anything, make sure no one is in range (ARRL).

Use a pulley, not the bare branch. A rope over a branch is fine for a temporary installation, but over time it digs into the wood or the tree grows around it and the rope seizes, so the antenna can no longer be lowered. A pulley or other low-friction bearing avoids that. The same article recommends black braided Dacron rope at least 3/16 inch thick, since most plastics deteriorate in sunlight (QST, October 2019).

Let the trees move. Trees sway, and a wire pulled tight between two of them will break or stretch. The Army’s field manual gives two fixes: attach a spring (or an old inner tube) at one end, or pass the rope through a pulley and hang a heavy weight on it to keep the antenna taut. Antennas supported by a tree’s trunk or a strong branch can usually survive heavy wind storms (FM 24-18).

Insulators. The antenna wire should touch only the feed point and its insulators. For improvised insulators, the field manual ranks plastic and glass ahead of wood and rope (FM 24-18).

At the feed point. A dipole does not need an RF ground, as long as common-mode current is kept off the coax; a current or choke balun at the feed point is the usual way to do that (ARRL). Ferrite on the coax blocks that current by adding impedance in its path (General pool, G6B10). A dipole with a single center support, the inverted V, needs only one tall support (antennas guide).

Check the SWR in place. An antenna’s SWR measured near the ground is wrong; measure with the antenna in its working position (Cushcraft).

Masts, tripods and roof mounts

Telescoping masts sold for TV antennas come in heights from 20 to 50 feet and are a popular, inexpensive support for small antennas. Aluminum extension ladders are sometimes used as temporary supports, for example at Field Day, but they are hard to walk up: do not try to raise one alone. Before you attach anything to a house or put an installation on a roof, have a qualified person confirm that the method is adequate and the loads are acceptable (ARRL, Antenna and Tower Safety).

Guys. Guy lines stabilize a mast, and they can be wire or rope. Metal guy wires near an antenna should be broken into short lengths joined by insulators so they do not affect it (FM 24-18; Cushcraft). For guyed towers, the ARRL’s rule of thumb places the anchors between 60 and 80 percent of the tower height from the base, so check that your yard has room (ARRL). Run a safety wire through each turnbuckle so vibration cannot loosen it (Technician pool, T0B05).

Towers. A tower needs a design by a qualified engineer for the wind and ice loads where you live, installation and maintenance to that design, and the inspection and maintenance the manufacturer recommends. Be cautious with used towers: have them professionally inspected (ARRL). If you climb, the pools teach “100% tie-off”, meaning at least one lanyard attached to the tower at all times, with lanyards attached to the tower legs and a shock-absorbing lanyard attached above your head (Extra pool, E0A07, E0A11 and E0A12). The safety guide covers the rest of the climbing rules.

Grounding the support. One antenna maker’s instructions call for grounding the antenna, mast and tower directly to one or more ground rods at the base with at least 10 AWG wire and non-corrosive hardware, and refer to the National Electrical Code for details (Cushcraft). A tower gets a separate eight-foot ground rod for each leg, bonded to the tower and to each other (Technician pool, T0B08). Your local electrical code sets the grounding requirements for a tower or antenna (Technician pool, T0B11).

Verticals and radials

A quarter-wave vertical is half an antenna; its radials supply the other half. A ground-mounted vertical needs a radial system to be efficient, with the radials on the surface or buried a few inches deep (Extra pool, E9A10; General pool, G9B06). Depending on your soil, a dozen radials may do, or you may need as many as 100. Some manufacturers make verticals that do not use radials at all (ARRL). On an elevated ground-plane antenna, sloping the radials downward brings the feed point impedance close to 50 ohms (General pool, G9B02).

Routing the coax

• Use cable rated for where it runs. Datasheets list where a cable may be installed. Belden’s RG-213 (8267), for example, is rated for indoor use, while its RF-400 (7810A) has a polyethylene jacket rated for outdoor use and resistant to sunlight and UV (Belden 8267; Belden 7810A). The jacket must resist ultraviolet light, because UV damage lets water into the cable, and moisture contamination is a cause of coax failure (Technician pool, T7C09 and T7C10).
• Do not bend it tighter than the datasheet allows. The minimum installation bend radius is 4 inches for RG-213 and 2 inches for RF-400 (Belden 8267; Belden 7810A).
• Seal every outdoor connection. Any connector used outdoors, whatever the type, needs careful weatherproofing (Technician pool, T9B01). The connectors guide shows how.
• Bring it in through a grounded entrance panel, described next.

Lightning protection where the coax comes in

Lightning protection goes where the feed lines enter the building: arrestors mounted on a grounded panel there, with the lightning ground system outside the building (Technician pool, T0A07; General pool, G0B04 and G0B13).

• Protect every line, on one panel. Each coax line leaving the station needs a protector, and so does every other line that leaves it: AC power, rotator control, telephone. All the protectors mount on a common plate connected to the outside ground system. The protection is all or nothing: a missed line can make the damage worse than having no protection (ARRL, Lightning Protection Part 1; Part 2). This single point ground panel exists to make all the protectors act at the same time, and the station’s AC surge protector belongs on it too (Extra pool, E4E13 and E4E14).
• Bond every ground together. Bond all external ground rods together with heavy wire or conductive strap, and bond the lightning ground to all other grounds, including the electrical service ground (Technician pool, T0A09; General pool, G0B11).
• Keep conductors short and straight. Make ground connections short and direct and avoid sharp bends (Technician pool, T0B01 and T0B10); the ARRL series suggests turns of 12-inch radius or larger (ARRL, Lightning Protection Part 3). Do not solder lightning ground connections, since the heat of a strike will likely destroy a soldered joint (General pool, G4C07).

Equipment that survives a strike does not mean you would: do not touch the station during a strike (ARRL, Lightning Protection Part 1), and do not operate while a storm is near, as the safety guide explains. Local electrical codes set the grounding requirements (Technician pool, T0B11), and the ARRL notes that most states adopt the National Electrical Code (ARRL).

Inspect and maintain

Follow the inspection and maintenance schedule your tower or antenna maker recommends (ARRL). Between inspections, watch the SWR: erratic changes can mean a loose connection in the antenna or feed line, and water in connectors, extra connectors and high SWR all add loss (Technician pool, T9B08 and T9B09).

Before you raise it: a checklist

1. The antenna, mast and guys are far enough from every overhead line that nothing can come within 10 feet of it if it falls, and preferably twice the height away.
2. You have checked permits, your deed or HOA rules, and, near an airport or above 200 feet, FAA notification.
3. You have evaluated RF exposure for the planned location.
4. Ropes run over pulleys, with a weight or spring to let trees move.
5. Guys are anchored, turnbuckles safety-wired and metal guys broken up with insulators.
6. The coax is rated for outdoor use, sealed at every outdoor joint, and enters through a grounded panel with protectors on every line.
7. Every ground rod is bonded together and to the electrical service ground.
8. A helper is with you, and no one is in range when you launch a line.