Scanner AND 450 mhz antenna?

[DarrenFishtrain]

Switching from car to 4 wheel drive truck for work.
I would like to get rid of my mag mounts and perm. mount them on the roof; but this means cutting holes in the roof -- obviously, I want to do it only once.

Both antennas are about teh same size. Transceiver is 25 watts.

I usually just toss the mags on the roof a few feet apart. The truck roof doesn't offer this much unless I go side-to-side.

what would be best?
centerline (front / rear) as far apart as I can get them?
centerline (left/right) of the roof, as far apart as I can get them?
both centerline F/R but close together?

I've tried the mag mounts on the hood and it's noticable worse than up on teh roof -- but their mag mounts.

 

[zz0468]

It's all a trade off. You'll NEVER get enough spacing to avoid interaction, so you might as well throw that idea away. Just space them as far apart as practical.

In mounting antennas on a vehicle, aesthetics becomes a concern, especially if it's the family car. Mounting a pair of antennas on the roof, it usually looks better if they're lined front to back, with the shorter one up front. Performance wise, it makes no difference.

You can get a bit more spacing mounting them side by side, as far apart as possible, but the difference in isolation isn't that much, so I only do that if I can make it look decent.

If you mount them too close to the edge, either front/rear or left/right, you'll probably skew the radiation pattern off from omni-directional, so mount as close to the center as you can for both of them, while maintain some separation. I usually shoot for about 12-18" between antennas.

You can beat your head against the walls trying to get scientific about it, and not have that much to show for it, performance wise. A vehicle mounted antenna is a compromise, and part of the compromise is ease of installation, how does it look, and how well does it perform.

 

[jassing]

I once spent a weekend trying to find the 'best' position for multiple antennas - (cell, scanner & cb & am/fm) From what I could tell the only thin that mattered was where I Put the cb antenna.. I never noticed a bit "oh, that's lots better" in an arrangement, but others noticed a weaker signal from teh cb at times.
So, what if you have multiple transmitters? (ie: more than one antenna sends, but never at the same time)