Batboard

For the antenna group:

I need to mount an NMO lowband antenna on my new Impala. I have two choices: trunk or fender....roof is not an option bcause of sunroof and low garage door opening.

Trunk has two NMO's on it now, side by side. My biggest concern is interaction with other antenna's, since I need to have a VHF 150 and UHF antennas back there with it.

I'm thinking fender with the highband 5/8 on the other fender, to keep the whips from smacking each other and/or screwing up the swr.

Thoughts?

I would put the lowband in the middle of the trunk with the UHF and VHF on either fender.....

Put the lowband on the trunk center or the roof center, as this antenna would become very directional if placed on the edge of the metal. It may also not tune out on the edge.
The Comtelco lowbanders set up really well and you'll usually acheive a 1.2 or lower VSWR reading.

If it's not going to be in the center of the roof or at least trunk, you may as well put a ball mount on one rear quarter panel and use a 1/4 wave.

The issue of all of the antennas together on the trunk lid is this: the high band and uhf antennas may well be a 1/4 wavelength (at the lowest frequency - high band in this case) away from each other. The 1/4 wave seperation is considered the minimum to avoid serious interaction. For the low band antenna, 1/4 wavelength is at least 54 inches (50 MHz - likely more since you may or may not be talking about the 6m ham band), getting the low band antenna at least that far from the rest is nearly impossible.

I also have the high band 5/8 wave and the UHF collinear on the trunk, 25 inches apart (over 1/4 wave on high band.) The low band antenna mount (used from 29 to 53 MHz) is a ball on the rear quarterpanel. I almost put it on the front fender, but elected to avoid that for ignition noise.

Good luck,

Check out http://www.sti-co.com for replacement antennas that take the place of the factory antenna.

So far it looks like the lowband antenna will be a ball mount 1/4w on the left rear fender...my primary VHF Hi antenna is a 1/4w on the roof, behind my sunroof, so there are 2 NMO mounts on the trunk that are open now for another VHF Hi and UHF.

Thanks for the advice! Time to convince myself to put a ball mount on a 02 Impala.....I need a beer

I may just put an NMO lowband antenna on the trunk to try it, but then the trunk will get cluttered with 3 antennas all with 100-125w TX. I can't win.

Here's a stupid question:

If it is bad idea to use an NMO mount on the outer fender as mentioned above, which I agree with, then why is the ball mount a better way to go? It's really out in mid-air with nuthin' but road as a groundplane??

Just wondering

Have you considered dual-band antennas?

007 wrote:Here's a stupid question:

If it is bad idea to use an NMO mount on the outer fender as mentioned above, which I agree with, then why is the ball mount a better way to go? It's really out in mid-air with nuthin' but road as a groundplane??

Just wondering :D

Well, from the ground plane perspective, it's not better. But the full 1/4 wave whip will work better than the base loaded short antenna. Keep in mind, anything less than 1/4 wavelength causes loss. It actually wastes your power. 1/4 wavelenght is considered unity gain. So while the ground plane isn't ideal, at least the antenna isn't costing you power.

Additionally, the further you can separate the antennas, the better off you are. So there are two advantages to the ball mounted 1/4 wave. I vote for that. The biggest problem with the incomplete ground plane is the potential for the thing being directional. And it will be - to a point. But only the user can determine - sadly through use - whether that will be a factor. It usually isn't that severe as to cause problems.

Good luck,

Thanks Chris. Guess I'll have to bite the bullet and put it on to find out.

Dual Band antenna's? I considered it for about 5 seconds until I had a vision of 110w X9000's into a duplexer that may/may not fail, taking out the other radio as I dump 110w right into the antenna jack.

I'm not a big fan of dual band's anyways...same principle as the loaded 1/4w for lowband....it is a compromise to get the antenna to work on both bands. Mono band antennas work the best.

I have never had any problems installing low band antennas on the fender, I have used the fender mounts and trunk lip mounts. The only thing I can suggest is to ground the trunk lid to the body using a good quality braid. I have used this method many times for our low band Syntor X9000 and MaxTracs. My low band antenna of choice has always been the Spectrum series by Motorola, costs about 45.00 but they are well worth it.

Fender mount, as in NMO fender mount? Or ball mount?

007, if you want to mount to the fender just use a right angle bracket with a 3/4 inch hole in it. It has 3 holes in the mount for self tapping screws. If you want to mount to the truck lid use a trunk lip mount with the 2 allen screws in it , Motorola makes one but I prefere the antenex one because it has a lower profile, and I personally think it is a bit better built. Any Questions or if you need any part numbers send me a email or a pm.

Thanks for the info, but there is no room for L bracket fender mounts on the Impala...the decklid clearance is too tight for the coax to fit thru!

I'm gonna stick with the NMO mounts.