New HAM, advice for mobile setup

[Airmapper]

I passed my Tech Exam, so just waiting for it to be "official" and I have a Baofeng HT in the mail for some initial use.

But I'm getting a bit of information overload looking at my plans for a mobile setup.

I think I have the unit narrowed down to the Kenwood D710GA. I find APRS cool, so that unit seems to be a good platform for APRS use.

I'd like to group as much as possible in a shipment to save on shipping costs some. So I'm looking for antennas. Well that opens up Pandora's box. My roof is a mess. Anyone familiar with Xterra's knows we have a lot of junk up top, and I have a full size roof basket that complicates this. I want an antenna that does well, yet can withstand some brush contact, and I don't want to loose use of my roof rack either. 99% of the time it's empty though. Fold down would be great.

First off I'm thinking perhaps a magnetic mount until I get some brilliant ideas, I do have "gaps" I can stick it in, but how is a metal framework suspended an inch or so above my RF ground plane going to freak out my signal?

Also, I have a half finished version 2.0 of the same rack in progress, any ideas on incorporating antenna mounts into it would be great, I still have an opportunity to customize it for later, although I'm in no hurry to finish it, I'm looking at light mounts and stuff as well. Also I'd like to retain my CB antenna, as it's still used a lot among 4x4's, so there is another complication and more junk up top to worry about in low clearance areas.

So any and all suggestions for a mobile setup, with all the considerations for an Overland/Off road bias, are appreciated. Below is a photo of what I'm working around, a 3' Firestik CB antenna is now U-bolted to the driver side tube in the center.

 

[AFBronco235]

How you mount your antennae depends a lot on which one you go with, as well as what kind of terrain you'll be driving through. If there are a lot of overhangs or branches, you'll want it to be flexible, so a spring is a requirement. You should also consider making the antennae removable for when you're not using it, or if you need your radio ready 24/7, consider maybe using two different antennae, and use a small one as a daily and a larger one for when you're on the trail?

I'm working on my own setup. Right now, I just have the little Boafeng UV5R with a roof mounted magnetic antennae for short range, but I plan on a heavier setup after I get my license. I already have the antenna mount setup for that. When I removed the stock tire rack on my bronco, I left the brackets for it and will be using those for the larger antennae and a few other things. I may end up sticking a smaller antennae on a telescoping pole mounted to those brackets.

 

[Robert Bills]

. . . I want an antenna [for my Xterra] that does well, yet can withstand some brush contact, and I don't want to loose use of my roof rack either. . . . Fold down would be great.

. . . I have a half finished version 2.0 of the same rack in progress, any ideas on incorporating antenna mounts into it would be great, . . . I'd like to retain my CB antenna. . . .

This thread on TheNewX.org may give you some ideas: http://www.thenewx.org/forum/showthread.php?t=142449

Excerpts:

Antenna mounts: 2m/70cm Ham (passenger side) - Breedlove NMO Roof Mount with ring terminal connection #78; CB (driver side) - Breedlove Pedestal Stud Mount #008 with Firestik medium spring and Breedlove quick disconnect coupling #002. breedlovemounts.com.

Antenna: 2m/70cm - Larsen NMO 2/70 SH; CB - Firestik 2' (in forested areas with low overhangs) or 3' Firefly (in open terrain).

Grounding: 1/2" copper strap from adjacent to the CB mount to the vehicle body under the rear hatch, and a second 1/2" copper strap from adjacent to the NMO mount to the vehicle body under the rear hatch. Powdercoat/paint sanded to bare metal under connections to drop in basket and vehicle body.

Footman Loops:

Footman loops were welded in locations that correspond to the straps on a Raingler Cargo Net for DepHep Racks (Raingler PN 112MCN). They make it easier to center the cargo net, especially in the dark. The footman loops are from McMaster Carr, Part No. 8030T13 - "Webbing Guide, Zinc-Plated Steel, 7/16" Clearance Height, for 1-1/2" Wide Webbing" - $8.94 for pack of 10).

Tabs for Antenna Mounts:

Rather than make them myself, it was cheaper and easier to purchase steel weld-on tabs and drill out the holes to fit my antenna mounts (Proto-Fab PN 74-375, sourced from my local steel supply house http://www.protofab.com/graphics/Tabs 2011.pdf ). I used 3 in the rear (the center tab will eventually be used to mount a reverse/work light) and 2 in front (for which I have no immediate use).

[Photo below.]

L-Brackets for Floor to Basket:

I also welded on some steel L-brackets to the inside of the lower framenear the corners to create mounts for a floor. (Proto-Fab PN 806 http://www.protofab.com/graphics/Brackets 2011.pdf.)

 

[Airmapper]

How you mount your antennae depends a lot on which one you go with, as well as what kind of terrain you'll be driving through. If there are a lot of overhangs or branches, you'll want it to be flexible, so a spring is a requirement. You should also consider making the antennae removable for when you're not using it, or if you need your radio ready 24/7, consider maybe using two different antennae, and use a small one as a daily and a larger one for when you're on the trail?

Lots of branches, yes. Removable (or tip over), yes.

I have a 3' Firestick on a HD spring, last few trips off road I left it up. I heard it bouncing around some, but it's holding up well to branches (and the occasional drive-thru.) So that tells me as long as it will give, I'm probably fine.

This thread on TheNewX.org may give you some ideas: http://www.thenewx.org/forum/showthread.php?t=142449

Thanks Robert, I was familiar with your setup but initially dismissed it since my rack extends back further than Dephep's, mounting them in the same location on my rack would set them over the rear hatch. However on closer inspection, with some adaptation I can possibly use similar mounting techniques in different locations. Most of that I'll have to implement when I finish my second rack. I also found the tab and base info useful.

Not to be critical of your setup, it looks nice, but I was hoping to center my dual band antenna over the roof. I guess it's a big battle between convenience and a good RF pattern.

 

[BettysNephew]

Check into the Austin Antenna 500c Soft Top. Very flexible mast and a spring below the loading element at the base. It will be hard to break.

 

[F40]

NMO mounts with these for each band. http://www.sti-co.com/antenna-products/public-safety-antennas/flexi-whip

 

[4x4junkie]

Not to be critical of your setup, it looks nice, but I was hoping to center my dual band antenna over the roof. I guess it's a big battle between convenience and a good RF pattern.

I wouldn't be as concerned about the RF pattern on VHF & UHF as on CB... The wavelength at VHF & above being much shorter means a smaller mass of metal under the antenna mount will be much more effective at functioning as a ground plane.

What I would suggest is mount the CB antenna at the front of the rack (giving it a more central vehicle location for it's longer wavelength to work best), then mount your VHF/UHF antenna(s) centered along the side(s) or opposite the CB ant (back maybe).
As mentioned, you want the rack well-grounded so you don't run into SWR problems... Having antennas mounted at the front of the rack means you should ground the rack at all 4 corners (the bolts holding your factory roof rails down should work fine as ground connection points if they are threaded right into the body itself).

 

[Airmapper]

Thanks for the antenna suggestions, looks like I have some good options. I'm thinking of getting a NMO magnet base and one of those flexy antennas, so when I finally decide my final design on the rack I'll make a tab, ditch the magnet, and move the antenna over. Finding a magnet mount that doesn't have a permanent cable attachment is going to be tricky, I hate to run cables over and over.

I wouldn't be as concerned about the RF pattern on VHF & UHF as on CB... The wavelength at VHF & above being much shorter means a smaller mass of metal under the antenna mount will be much more effective at functioning as a ground plane.

What I would suggest is mount the CB antenna at the front of the rack (giving it a more central vehicle location for it's longer wavelength to work best), then mount your VHF/UHF antenna(s) centered along the side(s) or opposite the CB ant (back maybe).
As mentioned, you want the rack well-grounded so you don't run into SWR problems... Having antennas mounted at the front of the rack means you should ground the rack at all 4 corners (the bolts holding your factory roof rails down should work fine as ground connection points if they are threaded right into the body itself).

Hmm, thanks. I think that would work very well. I have enough clearance for a tab at the front of the rack for the CB.

Grounding that rack will be, interesting... I have one flat strap at the center tube support, that is the most convenient access to the mounting screws. The corners would be more difficult. I'm assuming that is purely for electrical ground? If so 2 in the center may be sufficient.

 

[Hilldweller]

Did you notice mine when we were wheeling?

I have a KC light mount that I modded to fit an 18" flexi antenna. Works fine on the A-pillar and bends like a sapling when it meets a branch.
Don't forget that you've got lots of acreage up front to work with.

Welcome to HAM, btw. Now you can hear what Kos and I were saying about you...

 

[Airmapper]

Did you notice mine when we were wheeling?

I have a KC light mount that I modded to fit an 18" flexi antenna. Works fine on the A-pillar and bends like a sapling when it meets a branch.
Don't forget that you've got lots of acreage up front to work with.

Welcome to HAM, btw.

Thanks Bill, I noticed you had HAM gear but I'm afraid I didn't pay much attention to the mounting arrangement.

I considered the hood area. I'd prefer to have it on the passenger side if I went that route, but my FM (Public Broadcast) antenna is there. I wonder if I could splice it into a HAM antenna, I know the same antenna should receive those signals as well. Probably would burn something up when I transmit though. I may have to see if that is even possible.

Now you can hear what Kos and I were saying about you...

I thought profanities weren't allowed on HAM.... :sombrero:

 

[steve c]

Put it on the hood with one of these contraptions







When I first installed it, I thought the antenna would drive me nuts being in my line of sight. I don't even notice it anymore.

 

[4x4junkie]

Grounding that rack will be, interesting... I have one flat strap at the center tube support, that is the most convenient access to the mounting screws. The corners would be more difficult. I'm assuming that is purely for electrical ground? If so 2 in the center may be sufficient.

Ground points at each corner provides the best ground at RF (only one is needed for electrical (DC) ground however).
You can try it with the two in the center though. Maybe you'll get lucky (every situation is a little different). If the SWR is good, then you're golden.

 

[Robert Bills]

. . . Grounding that rack will be, interesting... I have one flat strap at the center tube support, that is the most convenient access to the mounting screws. The corners would be more difficult. . . .

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.

I would think that to bond your steel drop-in rack basket to the body and create an effective RF ground plane you will need to attach ring terminals to your ground straps, then place those ring terminals directly against the roof (i.e., under the OEM roof bar base mounts) with sufficient paint sanded away from the roof under the ring terminals so you get solid metal-to-metal contact.

 

[BigSwede]

Wouldn't it be simpler to use a half-wave antenna?

 

[Robert Bills]

Wouldn't it be simpler to use a half-wave antenna?

Perhaps for 2m, but it wouldn't solve the OP's issues with respect to RF ground plane for CB.