roof rack grounding for antennas

[DouglasVB]

Now that my sweet roof rack is on the truck, I'm looking at putting a 2M antenna on the rack. Currently the rack is electrically isolated from the truck at two different points (rubber on the crossbar feet and rubber between the crossbars and the actual roof rack). I can ground everything with a couple wires but my reading on the internet makes me think that won't be enough to create a good ground plane for my 2M antenna. I'm also not really wanting to grind up my roof and weld on grounding straps at all four corners of the roof basket.

Here's a picture of the roof rack:

I'll be throwing lights up there soon as well. Both a 52" light bar (thanks super cheap Chinese manufacturers!) and several work lights.

The antenna that I definitely want to mount somewhere on my roof is a Browning BR-180. I'm also thinking of where to place my 5' tall Firestik CB antenna. That one probably should mount somewhere at the rear of the vehicle once I make a rear tube bumper and tire carrier just because it would be so darn massive mounted on the roof. I also *might* put an AM/FM antenna on the roof to get it out of the way of the passenger's views for photography purposes. Hopefully I can find a reasonable retractable antenna to put in the stock location though. In the future I also want to mount a 10M antenna somewhere on the vehicle although that won't be until sometime next year.

So... four potential antennas. 1) 2M, 2) CB, 3) FM/AM, 4) 10M.

My questions are:

1. What do I need to do to turn the roof basket into a decent ground plane (in addition to the rest of the roof and truck) for my antennas?
2. Where else should I be looking to mount antennas? As we've talked about before in this sub-forum, the front bumper is out

 

[MileHigh]

The roof of your truck will be a good plane, whether you mount it on the roof itself or the rack. Try to make your grounding point as close to the antenna as possible and you should be good to go.

 

[DouglasVB]

I should be able to ground straight from the mount to the truck so that should be okay. Am I going to need to worry about the shape of the roof rack and basket with respect to radio wave propagation or anything like that?

 

[CardinalFJ60]

ground strap

I think I added a 1/2" braided ground strap from the rack to a bolt inside the rear lid. (fj60) ground is good on that rack now.

 

[DouglasVB]

I think I added a 1/2" braided ground strap from the rack to a bolt inside the rear lid. (fj60) ground is good on that rack now.

Where did you buy your braided ground strap from? I could ground it to one of the rear canopy bolts pretty easily... Hadn't thought of that before. Great idea!

 

[MDH33]

If it were me, I would just go for a hood/fender mount and a nice long antenna instead. You'll get much better performance and less likely to snap it off. I've run that setup on a couple of different Toyotas and had great results.

 

[DouglasVB]

No can do on hood/fender mounts forward of the cab. My co-pilot doesn't want the view for photographs cluttered with a forest of antennas. In fact, I need to relocate the AM/FM antenna even!

 

[MDH33]

No can do on hood/fender mounts forward of the cab. My co-pilot doesn't want the view for photographs cluttered with a forest of antennas. In fact, I need to relocate the AM/FM antenna even!

Wow. Is it really that hard to stop and step out into nature to get a shot?

 

[DouglasVB]

Haha yup it is when moving with the group. There are also quite a few shots that are gone in a moment or are located somewhere that it isn't desirable to stop.

 

[CardinalFJ60]

HRO or powerwerx.com

Where did you buy your braided ground strap from? I could ground it to one of the rear canopy bolts pretty easily... Hadn't thought of that before. Great idea!

I can't remember now, but I think I got it at HRr powerwerx.com when I was getting a bunch of Powerpole goodies. You can get them at either placeIIRC. what's nice is that they com in varying lengths/widths with ring terminals already attached.

 

[nakman]

Kinda have to agree with Martin here. Hands down your #1 best ground plane is smack in the middle of the roof- that is also the least practical for loading/unloading the roof rack, wheeling, garages, even drive through windows. You will be smacking antennas daily, and you'll break one unloading your roof rack one night when it's dark out. It's just not worth it, IMO.

How about those hatch mounts? Is there one you could run off the tailgate? My recommendation is 2m antenna on a tailgate/hatch style mount, use a mag mount CB for that 1 or 2 trips a year when the rest of the run doesn't have 2m, then a windshield antenna for FM. You can get the Bronco game on the ham- 450.050mhz, don't need AM.

Then way down the road, if you really get into 10m, put the antenna in back, opposite the 2m.

hatch mount:

windshield FM:

 

[Rezarf]

J.b Saunders sells grounding strap by the foot.

 

[DaveInDenver]

I have most of a roll of 1/2 braid of tinned copper, but it's way up north.

And, yeah, if the group you're traveling with doesn't tolerate stopping to snap a photo or just enjoy the world you're doing it wrong.

FWIW, I drilled two holes in the roof of Imelda and will do the same in the new truck. Once I get my NMO hole saw back. Not sure it where it is, tho.

 

[Seldom Seen]

couplw of ?s

1) Are you using a "ground plane" antenna?

2) Have you tried mounting your antenna and are having problem getting it resonate with in the band or getting an impedance match?

-OR-

3) you haven't tried it and you're looking for the solution to a problem that may not exist?

I'm willing to bet that as long as you make good electrical connections between the sections of the rack as well as the antenna mount and rack, everything will be fine and no aditional grounding will be necessary on 2 meters.

 

[DouglasVB]

Let me see if I can answer everything in one post... And thank you for all the ideas and discussion! It really helps me to work through potential ways to make this all work.

The 2M is not a ground plane antenna. The ground plane is the truck.

I haven't tried mounting it yet. Soon though.

The rack is completely ungrounded at present. There are two different sets of rubber insulators (rubber hose used as vibration dampers) between the rack and the truck roof. I figured that grounding the roof rack with a 14 gauge copper wire probably wasn't going to cut it. Ground straps seem like the likely next step.

Mounting the 2M on the rear hatch area is a bit problematic but not impossible with the plans I have for this winter. I will be building a rear bumper probably this winter that will then have a place for the CB antenna most likely. It could have a home for the 2M at that point, too. So it could go on the bumper/tire carrier that I will make.

The 2M antenna attaches to a NMO mount so it shouldn't be too bad taking the antenna off when I need to put the truck somewhere that is low. The roof rack really is more of an excuse for a place to mount the HUGE light bar I just got. Also occasionally I'll put a few light duffle bags up there and my shovel and axe will be mounted on the sides.

Putting antennas on the front is a no-go. In addition to not wanting antennas blocking photographs, we had the CB antenna on the front bumper for most of the summer and it annoyed me mildly and did not win me any favors with my partner. I'll also probably never put on brush guards (wire from the front bumper to roof rack to keep tree branches away from the windshield) that are permanent for the same reasons.

I had originally wanted antennas on my front bumper and hood like what I saw in the outback in Australia because it looks really cool but it doesn't work day-to-day for us at this point in time.

That windshield FM antenna just might work...

 

[nakman]

That windshield FM antenna just might work...

pretty poor for reception, for the record, but around town it's fine, depends on what radio station you listen to and how much power they have. I can get 93.3 just about anywhere. But something like classical 88.1 it's a little spotty. Long trips we're running off a phone/ipod anyways.