Sleeve dipole antenna for Meshtastic at 915MHz

Sleeve dipole antenna for Meshtastic operation at 915MHz.

That's proof of concept built starting from dimension of a ZIISOR antenna that was tested and not being resonant at 915MHz.

ZIISSOR 915MHz Antenna where it started from

Bill of Material #

Brass pipe, outer diameter 10 mm, inner diameter 9 mm, length >75 mm (sleeve)
Brass pipe, outer diameter 2 mm, inner diameter 1.4 mm, length > 85 mm (radiating rod)
Coin, outer diameter >10 mm, e.g. 0.01€ (sleeve end cover)
PVC/Vinyl pipe, outer diameter 15 mm, inner diameter 14 mm, length >180 mm
PVC/Vinyl sheet, thickness 2-3 mm
Foam for spacer

Semi-rigid coax might be expensive and not easy to source. A cheap solution is a combination of RG-316 inside a brass pipe. Either including the shielding or just the inner conductor with isolation. (with shield recommended)

Dimensions #

Final build dimensions

Sleeve length: 75 mm
Sleeve outer diameter: 10 mm
Sleeve inner diameter: 9 mm
Sleeve material: Brass
Semi-Rigid Coax type: UT-141C / SR141CUTP
Semi-Rigid outer diameter: 3.6 mm
Semi-Rigid conductor diameter: 0.92 mm
Semi-Rigid total length: ~100 mm
Radiator length: 80 mm
Feed socked: SMA type flange mount for UT-141C
Protection pipe outer diameter: 15 mm
Protection pipe inner diameter: 14 mm
Protection pipe length: 175 mm
Protection pipe material: PCV/Vinyl

Build steps #

1 - 4 #

Follow the build steps as shown for the 869MHz antenna.

5 - Completely assembled #

Foam spacer to center the antenna inside protection pipe.

Lower foam spacer keeps the sleeve centered.

6 - Impedance measurement results #

Tuned to -22dB @ 915 MHz inside protection pipe.

Corresponding VSWR 1.17 @ 915 MHz inside protection pipe.

7 - Final antenna #

Simulation results #

👈 Home