Antenna Selection and Mounting

The antenna matters more than the radio

For a fixed repeater, the antenna is often the most impactful upgrade available. Moving from a 2 dBi stock antenna to a 6 dBi vertical on a rooftop pole can add 4 dB of gain while simultaneously improving line-of-sight.

Antenna types for repeaters

Omnidirectional vertical (most common)

Radiates equally in all directions horizontally —- ideal for a repeater that needs to serve a wide area. Higher gain (dBi) concentrates the signal closer to the horizontal plane, extending horizontal range but reducing coverage of areas directly below. For elevated repeaters, 3–3 - 6 dBi is usually optimal. Very high gain antennas can create a dead zone directly beneath them.

Directional (Yagi, patch)

Focuses energy in one direction for maximum reach between two specific points. Requires careful aiming and is not suitable for general area coverage.

Gain vs. coverage angle

Gain	Horizontal range	Best use
2–2 - 3 dBi	Short	Ground-level or indoor use
5–5 - 6 dBi	Medium–Medium - long	Most rooftop repeaters
8–8 - 9 dBi	Long, narrow beam	Tall towers covering flat terrain

Cable quality

Coaxial cable losses add up at 915 MHz. Use the shortest cable run possible. For runs over 3 meters, use low-loss cable (LMR-200 or equivalent). Weatherproof all outdoor connector joins with self-amalgamating tape or appropriate connector covers.

Key mounting rules

• Mount the antenna as high as practical, clear of obstructions in all directions
• Keep the cable run short —- locate the radio enclosure close to the antenna rather than running a long cable
• Use stainless steel hardware outdoors to prevent rust and galvanic corrosion
• Never power on the radio without an antenna connected —- transmitting into an open connector can permanently damage the transmitter