How far apart should I space a Watson 7900 dual-band antenna, and a 1/4 wave whip for 4 Metres, to minimise any adverse interaction?
The vehicle is a Landrover Discovery with the two sun roofs, and the split level roof.

There's not enough space for them not to react.
Will it matter, probably not, unless you are very unlucky.

Cheers

Tony

Seconded. My friend, M0KXQ, has four antennas on his roof of his astra van. Did actually at one point get near double figures on the whole car. There's interaction and its a bit directional but they work.

Thanks Tony, and Connor.
The Disco is a great car for getting about in, and for carrying two 18 ft sea Kayaks on the roof, but those sun roofs are a PITA. Doesn't leave much metal for a ground plane.

Do bonding across the hinges of the bonnet to the body and the tailgate to the body. Read up on the bonding page at www.k0bg.com

But, probably, not worth the effort, for VHF/UHF only.

Cheers

Tony

70 MHZ is the lowest frequency I'll be using.