Magnetic Mounts

Magnetic mounts put a CB aerial on a roof or boot lid without drilling. Single base models run from the Sirio MAG 145 PL and Falkos MAG 145 to the 150mm BA150 Universal, the PNI 170/PL at 170mm and the 7 inch Turbo-S. Triple magnet bases spread the grip wider: the Trimag-S at 30 x 30cm and the compact Trimag-SB on three 95mm magnets.

  • Fitting: match your aerial first. SO239 on the Sirio, Falkos, Turbo-S and both Trimag bases, 3/8th on the TURBO-38170, a 16mm aerial hole on the BA150.
  • Cable: 4 metres of RG58 with a PL259 plug fitted on the Turbo-S, Trimag-S, TURBO-38170 and PNI 170/PL, 3.6m on the Sirio.
  • Paintwork: rubber base or boot on the BA150, PNI 170/PL, Turbo-S and TURBO-38170, silver foil on the Trimag-S.

Our guide explains why a magnet on the roof makes a working ground plane, and where to place it.

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One big magnet or three: which cb aerial mount holds a whip steady?

Fitting aside, the choice here is how the holding force is spread, and how tall the aerial above it will be. A magnet grips by contact, so the same pull spread wide behaves differently at speed from the same pull in one disc.

A single large base gives one unbroken contact patch. Moonraker put it plainly on the Turbo-S Large: more contact area means a steadier hold at speed and a larger ground plane than a small mount can offer, which is why they point it at longer whips and heavier loaded aerials. The PNI 170/PL works the same way at 170mm, listed for grip and stability even in high speed conditions. Three smaller magnets take the other route. The Trimag-S spreads the hold across a wider area of the panel, which, in Moonraker's words, is what you want when the aerial is tall enough to catch the wind at speed. The Trimag-SB does that on three magnets of 95mm each while keeping the base compact, so it sits tidily on a car roof.

If you expect to change whips, read the socket rather than the magnet. The TURBO-38170 is described as a practical choice for anyone who swaps aerials, because 3/8th is the thread used by a wide range of CB and amateur whips. The BA150 Universal is the other pattern: no socket, a 16mm antenna hole the aerial passes through, so check your aerial stud suits that hole.

BaseMagnet geometry as listedWhat the listing says it suits
Turbo-S LargeOne magnet, 7 inchLonger whips, heavier loaded aerials
PNI 170/PLOne magnet, 170mm, slimStability at high speed
BA150 UniversalOne magnet, 150mmDrill free fixing, moved between vehicles
Trimag-SThree magnets, 30 x 30cm baseAn aerial tall enough to catch the wind
Trimag-SB CompactThree magnets, 95mm eachWider footprint on a compact base

The check people get wrong: the panel underneath has to be bare ferrous steel, which most of these listings spell out, ruling out aluminium, glass fibre, plastic and composite. Because that panel is the ground plane the aerial is tuned against, the reading changes when you move the mount from roof to boot lid, or onto another vehicle. Test the panel with a loose magnet first, then reset the SWR after every move.