"PES949" wrote in message
...
I am thinking of getting a Twin Trucker for my Ford Explorer...

I would mount the antennas to the roof rack and run a ground wire since
the
racks have a rubber gasket to prevent leaks. I also want to use springs at
the
base in case I get some low branches etc.

The rack isn't the best place to mount them, the ground is marginal at best.
Can you get 9' separation, or close to it, on the explorer?
Co-Phased antennas need to be run at 1/4 wave separation, to get the
front-back pattern they are designed to deliver. When you deviate from that,
the pattern turns to slop.

Springs won't affect it much, just reduce the antenna length to compensate.

I know what you mean about height.. On my current rig, the front antenna is
a $150 Diamond Super-gainer that tops out around 10' off the road. That one
is too heavy for any single mag mount, and if you did, when it falls over,
it will break the coils. It dosen't bend either.. It just rips the roof out
if you hit something.

The Cobra 6000 is on a mag mount in the back center, which is working fine.
On the Explorer, I mounted it through the roof, near the back, with a
large-footprint bulkhead mount to spread the stress. There is room, up under
the header back there, to accomodate the connector and such.

The roof metal is better on the explorer though, than my current rig.
Here's what I had to do, to mount a ham antenna that's probably lighter than
what you're considering, on the Expedition.
http://www.inchase.org/outflow/event...2/f5Mount.html