HAM and CB mounts in new 4Runner

[MrGrimm]

Thanks for all the info guys. I will probably run another Wilson 1000 for the CB because I had a great SWR (1.1) and never had problems with it for a couple years. The HAM I am looking at a Larson antenna. I would like to keep the Firestik and run that because I already have the antenna but sometimes the easiest things are not the best.

 

[1911]

The difference in counterpoise whether it were centered over the truck or lip mounted wouldn't amount to a perceptible difference on FM.

In my experience, it makes a significant difference depending on what kind of antenna you use. A 5/8 or 1/4-wave 2m antenna needs a good ground plane to tune up acceptable SWR, while a 1/2-wave is much more forgiving. Again, my experience only, YMMV.

 

[xtatik]

I have a Diamond K400 NMO lip mount and it's worked great, except that the black paint (or is it powder-coating?) on the forward-facing part of the mount has worn completely away after about 2 years. Granted, I put quite a lot of miles on my truck, but I still think whatever paint/powdercoat they used was crappy stuff. Other than that, I've been really impressed.

Precisely my experience. All of the Diamond lip mounts I've used over the years have had 4 set screws.....four very tenacious set screws. You will absolutely cream any antenna mounted on them long before they let go.

As for an explanation of my comments on a "perceptible" difference between mounting types or positions.....The first thing you need to understand is that any place they are mounted will be crappy. Your vehicle makes for a lousy counterpoise. Your vehicle is going to be mobile and passing through varied terrain offering both good an bad "near field" and "far field" effects. This will change from good to bad and back again in seconds as your vehicle is in motion and encounters them. With all the variables your antenna will face while performing its duties, it's never gonna' get a fair deal. If you've read on the interwebz that ********** in the center with an NMO is best....I won't argue with that. If someone sez they audibly gain an additional (insert amount) of db gain due to the position.....I call BS.
The reality is, when dealing with an FM signal you're either in to the other receiving station (repeater, or whatever) or you aren't.
As an example: Let's say we're parked and we've place identical antennas on mounts both in the center roof and on a corner of the vehicle. We've done so with equal consideration to proper installation in each case. While you sit at the radio carrying on a conversation with another station 60 miles away, I'm in the back seat and secretly toggling a switch between them....you would either not notice or would barely notice any difference as I did so. If you were to notice, I'd tell you to begin driving in a circle while we continued. Suddenly, that barely perceptible difference evaporates. I've done this type of antenna shootout a couple of times with various antenna and mounts and while theoretically it can seem like there is a difference you will not audibly notice one.

 

[cruiserlarry]

I picked up a Diamond lip-mount the other day that has 4 set screws, but just the same I concur. Not good for a heavy antenna.

I run the Diamond K-400 lip mount off the back door of my FJ Cruiser, with a Yaesu ATAS-120A, which is a large, heavy tunable HF antenna. No issues for 4 years.

Regarding the powder paint, I've had the same problem with peeling paint, even though my mount is at the rear...I believe the plate is made of stainless, in which case it is very difficult for powder paint to adhere well - very little porosity to "grip" with. I just picked up a spare mount just in case, so I might change 'em out if the paint gets to me...:bike_rider:

 

[Hedge]

I've done this type of antenna shootout a couple of times with various antenna and mounts and while theoretically it can seem like there is a difference you will not audibly notice one.

The details of this experiment would make a fascinating write-up for eHam.net or a similar forum, perhaps even here. I can appreciate that the theoretical primacy of the roof-centered NMO mount may be reduced by other factors encountered in practical applications. I know that I, for one, would love to read all about your experience while I'm having my Saturday morning brew.

 

[trump]

I run the Diamond K-400 lip mount off the back door of my FJ Cruiser, with a Yaesu ATAS-120A, which is a large, heavy tunable HF antenna. No issues for 4 years.

To each their own... I have been watching mine flex the metal on the hood of my Tacoma for the last couple days with only a 34" whip. Can't imagine what it would do if I slapped my cb antenna (4' Firestik) on it.

 

[xtatik]

The details of this experiment would make a fascinating write-up for eHam.net or a similar forum, perhaps even here. I can appreciate that the theoretical primacy of the roof-centered NMO mount may be reduced by other factors encountered in practical applications. I know that I, for one, would love to read all about your experience while I'm having my Saturday morning brew.

It was hardly what I would call an experiment. In that instance, it was just a day spent moving three different commercially available antennas from two or three positions on two different vehicles. In another instance, it was a comparison between two identical vehicles (an Xterra club run) with identical radios and antennas. The antennas were not mounted in the same locations however and there was no audibly discernable difference. We were working with my 259b for the usual tuning procedures, but I don't take notes anymore. Back when I didn't know any better, I obsessed over this stuff. I'd look at another hams mount that would seem to be in a miserable placement and wonder how it could possibly get a decent signal out (or, even tune for that matter). But, I'd find he could hit the same distant repeaters that I could.
Truth is, although there are already plenty of threads over on eham and QRZ that revolve around this subject, with the exception of a few characters there, most of the hams don't give it as much consideration. There seems to be a greater concern on this site with getting FM antennas placed properly for optimum performance and of course there are also those who are concerned with cosmetically getting that patented "expedition truck" look, which of course wouldn't look complete without an antenna or two. There is nothing wrong with this, it's just my opinion and it's borne out of my experience with FM antennas mounted on different commercially available mounts. A reasonable mount placed using the mfr'rs recommended method has rendered results for me that were indiscernable in actual service. I think placement concerns here should be more focused on mounting them in places that offer at least some protection from obstructions or where they can be easily/quickly folded out of harms way.

 

[ScoutII]

The difference in counterpoise whether it were centered over the truck or lip mounted wouldn't amount to a perceptible difference on FM.

I read through the post and your experiments. Yes you are correct most of the time you are trying to hit a repeater, so it can become a mute point.
Looks like you covered most of the issues, like having it on the roof, since FM is line of sight this will help with range. Running a 5/8 wave over a 1/4 helps too. Good antenna installations it what it's all about. I need to read through the stickys. But some guidelines and tips would be most helpful.
There are a lot of products out there with just cable, and connectors.

Edit.. adding a picture of radiation patterns of antennas. The 1/4 wave has an egg shape,meaning it transmit and egg pattern and has less range over a 5/8 that transmits a flatter pattern. The pictures are from this site click here