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Docs Radio & RF Design Antenna Mounting

Antenna Mounting

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How to mount the antenna on the beacon case: SMA flange, panel mount, strain relief, and keeping metal away from the radiator.

Antenna Mounting

The best antenna is useless if it is mounted badly. The mount does three jobs: hold the antenna, connect it electrically, and keep the surrounding structure from detuning it.

Mount types

MountProsCons
SMA panel mountStandard, swappable antennasRequires a cutout and nut
SMA flange mountLower profile, self-sealingFixed orientation
Direct solder (whip)Cheapest, most ruggedNot swappable

The beacon’s recommended build uses an SMA panel mount on the case top, with the antenna outside and the radio inside.

Keeping metal away

Every metal object near the antenna detunes it and absorbs radiation. The rules:

  • Keep the antenna at least 30 mm from the battery, the ESP32 board and the OLED.
  • Route the coax away from the radiator.
  • If the case is metal, the antenna must be fully outside it, and the case acts as the ground plane (which is good, see Quarter Wave Antenna).

Strain relief

Field gear gets dropped. A whip antenna snapped at the connector is the single most common field failure. Mitigations:

  • A short rubber boot over the SMA base
  • A guy line or sleeve for long whips
  • Recessed mount so the antenna bends rather than snaps

Water ingress

The SMA connector is a water path. Seal it with a silicone gasket or dielectric grease at the flange, and keep the connector threads dry. See Waterproofing for the full procedure.

The 1 cm rule

A practical check: if the antenna can be bent so the metal parts of the case touch it, the mount is wrong. Recess or extend it so the radiator is always clear.