Antenna Mount Bracket for 1.667" Mast

Side-saddle bracket for mounting a mag-mount antenna ground plate to a vertical antenna mast. Designed for receive-only SDR setups (RTL-SDR, Airspy Mini, etc.) where you want to add a proper steel ground plane without occupying the mast top.

How it works: The saddle wraps 150° around the mast and is secured with two standard hose clamps (or heavy zip ties) through recessed slots that keep the bands from walking. A horizontal shelf extends from the saddle and holds a steel ground plate — the mag mount antenna sits on the plate. Three triangular gusset ribs under the shelf carry the cantilever load back to the saddle body.

Fits:

• Mast OD: 1.667" (42.34mm) — as printed

• Modify mast_od in the .scad to fit any mast diameter

• Shelf: 110x110mm with 4x M4 clearance holes on an 80mm square bolt circle

• Compatible ground plates: Hubbell RACO 833 4-11/16" galvanized box cover (used in this build), 8" galvanized duct end caps, or any flat ferromagnetic steel plate up to ~150mm

Hardware needed:

• 2x stainless hose clamps, 1-3/4" to 2-3/4" range (fits saddle OD)

• 4x M4 stainless bolts, 1" length + flat washers + wing nuts (wing nuts recommended for tool-free removal)

• Steel ground plate (verify ferromagnetic with a fridge magnet before buying)

Print settings:

• Material: ASA recommended (UV and heat resistant for outdoor/roof use). PETG works indoors or sheltered installs.

• Orientation: shelf-down on the bed, as modeled

• No supports needed

• 5+ perimeters, 40% infill minimum on the gussets

• Layer height: 0.2mm

My build:
Airspy Mini + ADSB radio monitoring, roof-mounted at ~300ft elevation. Ground plate is a Hubbell RACO 833 galvanized steel box cover from Lowe's (~$9), bolted with M4 wing nuts for tool-free plate swaps.