VHF Base Antenna

last updated : 2020/04/15
Code Description Budget Price Ship. weight Ship. vol.
ANTENNA, VHF, base, SkyMasts S.M4-165, 5.7dBd, 155–175MHz CH 1 353,50 26kg 0 Add


General information

The S.M4 is an array of four dipoles mounted on an aluminium mast.

Each folded dipole balun assembly and harness junction is completely encapsulated in poyurethane resin, preventing moisture ingress.

The dipoles can be easily oriented on site or before shipment to adjust between omnidirectional and directional patterns, and beam tilt is easily achieved via the parallel feed. The VHF antenna disassembles to reduce shipping costs, and the boom can be supplied in two parts if requested.

The balun assembly has been tested to BS5490:IP67.

Purchase via HQ recommended (compulsory for ICRC)


Frequency range

Typical: 155–175MHz or 176–192MHz

Input impedance

50 Ohm

Typical bandwidth

+/- 5.5% of Centre Frequency


< 1.5:1

Front-to-back Ratio

7 dB (offset)

Maximum input power

250 W



Forward gain

Omni: 5.7 dBd

Offset: 8.7 dBd

3dB Beamwidth

E-Plane: 21°

H-Plane: 180° (offset)

Standard connection

3m length of RG213 with N female type connector


12.7mm dia. x 1.6mm wall aluminium alloy grade 6063T6

Support boom material

VHF: 63.5mm dia. x 6.3mm wall aluminium alloy grade 6082T6


Stainless steel grade A2-70

Dipole clamps

Cast aluminium alloy

Dipole adjustment

M8 Stainless steel screws

Saddle clamps

Diecast Al/Zinc alloy

Balun encapsulant

Polyurethane resin U-600

Lightning protection

Direct grounded





Typical wind load @ 45m/s


Spare parts and accessories


Latest update: 15/04/2020

Options / Accessories