New HAM, advice for mobile setup

[Airmapper]

I am not persuaded that attaching a ground strap to the Xterra roof rack mounting screws will be effective. It is my understanding that the fasteners for the rack base mounts are screwed into rubber or composite nutserts, which would insulate the mounting screws from the body.

When I attached my ground strap to one of the roof rack mounting bolts, I confirmed continuity with chassis ground. They do carry electrical current through the body per my multi-meter.

Beyond that I do not have the technical knowledge or equipment to analyze it further, but I can say for sure that a no resistance connection was made from my ground strap, to the ground point of my 12V plug, indicating it travels throughout the vehicles ground system.

I'm not too happy with my current CB antenna setup, but at one time I had negligible (needle barely moved) SWR readings on CH19 using that ground strap.

 

[Airmapper]

I guess my biggest question / concern at this point is between rack mounting and hood mounting.

My little Comet M24-M mag mount is doing fairly well. I had an APRS contact at 70 miles assuming no hidden non reporting digipeater. It's right in there with the roof rack, and still seems to work.

My hood mounting option is probably going to be on the passenger side out toward the end of the hood. Drivers side has my snorkel in the way sort of.

I've read information that says the roof rack creates ground plane issues, even for VHF/UHF

Since the GP should also be 1/4 wavelength in diameter, rack mounting does not work well for VHF & UHF, because they are too far from the roof, and try to use the rack as a GP, which isn't as efficient as the roof. Even if the rack is grounded to the body with a wire or strap, it isn't RF coupled to the roof, and the bars will try to act like radiators, scattering the signal in an ineffective and unpredictable pattern for all frequency bands. Even a CB can't effectively get a good RF coupling through a rack. The ground plane needs to appear solid to the RF radiation in order to effectively radiate its energy out in a usable pattern. So a roof rack would have to have a metal (or wire mesh) floor in order to be a good GP.

On that note though, if I could create a ground plane into the rack. (About 1'-8" diameter I think) it may work well. But ideally I don't want an antenna in my rack, defeats the purpose of having a rack if I ever want to use it for cargo.

 

[4x4junkie]

I've used rack-mounted antennas several times... No it may not be a 100% perfect ground plane, but as long as the SWR is good, any imperfections in the signal pattern are unlikely to be noticeable (I certainly didn't notice anything when I moved two antennas that were on the roof to a rack that went over the previous location of the antennas). Mounting the antenna along the side(s) of the rack shouldn't interfere much (if at all) with the carrying of cargo.

 

[Longrange308]

when I installed the 2m in my Xterra, I really wanted it to be as streamlined as possible.. This is what I came up with.. Range was excellent, and the antenna was never in the way.. It was just there and it worked really, really well.. Access to get the NMO mount in there was not all that bad either.. Just had to pull the map lights down and fit squeeze my hand in as best as I could.

Well, here it is installed. It doesn't stick up too much over the roof line and it has a spring in it to help it last if it contacts a branch..


Location.

Untitled by LongRangePro, on Flickr

I used an NMO base mag mount, so I can drill a hole later and go true NMO, but I'm not totally committed now. Wanted it to be inconspicuous so I put it dead center in the roof but partially under the fairing. I also lost zero storage up here too!

Untitled by LongRangePro, on Flickr


Untitled by LongRangePro, on Flickr


I wanted to hide the unit in one of the glove boxes, but that didn't work, so this was my second choice and I actually think it's the best, with the exception of under a single din radio in the stock double din radio location.

 

[Wh1t3nukle]

I have a basket over the bed. It's floor is expanded metal. I currently put my mag base antenna on the basket floor, all the way forward. Perhaps a foot from the cab and maybe 2" below. I've had great response with it via simple radio checks with others. I'm now looking to move towards a permanent mounting though. I pull the antenna back into the cab via the window when not in use. I'd also like to move my CB antenna up to the basket. Currently it's at the driverside stake bed (102" whip). Going to the basket and change to shorter whip. I'm encouraged with your input of placing to the sides of the basket (e.g,. cb driverside, dual band passengerside).

Few options from looking around my though was to have a spring (trees), but also a mount that can fold down. Anything flawed with this?

I've used rack-mounted antennas several times... No it may not be a 100% perfect ground plane, but as long as the SWR is good, any imperfections in the signal pattern are unlikely to be noticeable (I certainly didn't notice anything when I moved two antennas that were on the roof to a rack that went over the previous location of the antennas). Mounting the antenna along the side(s) of the rack shouldn't interfere much (if at all) with the carrying of cargo.

 

[4x4junkie]

Few options from looking around my though was to have a spring (trees), but also a mount that can fold down. Anything flawed with this?

Shouldn't be any issues with that, just be sure to get a quality fold-over mount for it (Hustler & Breedlove are pretty much the only quality brands I've seen in 3/8-24 CB antenna hardware).
Also, don't switch to a CB antenna shorter than 5 feet, otherwise you'll give up everything you may have gained by moving the antenna up higher (and then some). Keep the 102" whip if you can.

 

[Airmapper]

I've been meaning to post back with what I came up with, but I never took good photos, maybe this weekend I'll remember to take some.

I went with a hood mount, I use a fender bolt so no mods to the truck whatsoever. I bent a piece of stainless sheet metal so it comes out the hood gap, and used a folding Comet SBB-5NMO.

However how I have it now can be either permanent or temporary.

 

[steve c]

Nice!

Good work on the homebrew hood mount.
I was just going through a box with some leftovers from recent projects and stumbled across my hood mount packaging. It was like $80! It's clean and functional, but a bent piece of sheet metal probably would have accomplished the same result for a few bucks. Oh well!

 

[Airmapper]

Nice!

Good work on the homebrew hood mount.
I was just going through a box with some leftovers from recent projects and stumbled across my hood mount packaging. It was like $80! It's clean and functional, but a bent piece of sheet metal probably would have accomplished the same result for a few bucks. Oh well!

Thanks, here are pics: