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Mobile antenna installation


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Hi Gentlemen,

I recently got a magnetic 1/4 wave antenna for my mobile radio.   But my 2017 F-150 is aluminum.  Do I have any other options than a bumper-mount antenna?  I'd really prefer to mount my antenna on top of the cab for better performance.  I considered somehow mounting a steel plate on top of my truck cab so the antenna will stick to it, maybe with some epoxy.  I think I read somewhere that part of the magnetic base of the antenna needs a ground though.  Is this correct?  If my metal plate isn't grounded to the vehicle, will the antenna still work as it's supposed to?  Will the ground plane created by the top of the truck cab be good enough or does the antenna need a physical ground such as being placed on a steel truck cab?

Thanks
KO4QDG

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ELMER

Hi Anthony.

If you want to start an argument, put two physicists into a room and have them discuss the merits/value of truck as a ground plane. That's my first cautionary tale. Now for some options 😎

The truck itself is going to give you lots of ground, especially the aluminum which has a conductivity ± three times higher than steel (36.9 vs 10.1 x 10.E6 Siemens/m). On that front you're good. Now comes the age old question of bonding for ground vs. mutual capacitance. Great article here (http://www.k0bg.com/bonding.html) by K0BG. Basically, he's giving you ways of actually bonding to the truck. Is it 100% necessary? In my 'opinion' it's not necessary but it will be an improvement. But frankly, your bonding will be moot if you can't get close enough to a bonding point, and that's tricky from the middle of the cab roof. Also, many of the modern trucks, not sure about the 2017 F-150, have plastic paneling or even when metal, discontinuous installs.

So now comes the hard part, how do you mount the antenna? If you're willing to drill, good to go, right there smack dab in the middle of the roof. But yup, that's a hole but at least you'll be directly connected to the aluminum. If you don't want to drill, you can do an online search for a self adhesive steel plate that can be stuck on top of the roof. Though you will someday be able to take it off, you'll still be left with a mark from the absence of sun and grit below the plate. Regarding the ground with this scenario, I have never tested it but I assume there is some conductivity left, despite the adhesive layers. Next, you're right about no-go on the bumper. Bad transmission patterns - guaranteed. That 2m signal does not want to go through the truck. Mirror mounts are another option as long as you have a bracket based system; the modern plastic mirrors are obviously not an option. The morror positioning will also skew your pattern, but you will likely be much closer to a ground. And then there are those big, ugly suction cup mounts. If you don't mind those, the advantage is that you can occasionally take it off and wash underneath and let your paint 'breathe'. The triple suction mounts are solid. I've used them multiple times and they will hold pretty much any antenna.

As I hinted, options but no real solutions. In fact, the question you pose is one of the most often asked ones. What would I do? I would likely do what I've done in past, but it's not cheap. I actually bought a roll bar 😇 The bar went behind the cab and then I drilled into the middle of the bar. I had full bonding, central positioning and acceptable aesthetics. If you use the roll bar, you can always use a clamping system instead of the drilling - easier and works just as well.

Oh, one more thing to really confuse you. Some people (I admit that I have in past) also go as far as installing an anti-static under-vehicle strap that actually drags on the ground. Maybe overkill and a definite cause of argument among physicists. 😂

As always, hope this helps.

Jim

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Anthony-

I'm going through the same consideration right now - I recently acquired a 2018 GMC Yukon XL, and I'm looking to permanently mount a multi-band antenna on it. We're doing some long family road trips this summer, and I want to have a proper mobile rig installation for that, as we'll be in some pretty remote places for some of the journey.

Like Jim, I'm a big believer in center-of-roof mounting for best omni-directional ground plane, but this vehicle will have a "photon torpedo" cargo box on top of it for much of the traveling it will do this summer, so the natural location for a drill-mount antenna won't work. Nor can I move that mounting location forward on the roof, as there is a sunroof installed.

My research has directed me towards buying a Comet 3/4" fender mount that is designed for the truck:

https://www.hamradio.com/detail.cfm?pid=H0-013680

and they make one for the F150 as well:

https://www.dxengineering.com/parts/cma-fo3antncg

It is designed for you to bring your own NMO mount (that's my plan, I have a number of Larsen NMO mounts already). I plan to install it on the passenger-side front fender. I'm leaning towards buying a new antenna to go with it, likely in the 40" range, as I'm not looking for it to be too tall, given it'll already be over 36" off the ground! I'm not sure which I'll get - it'll be used with my Icom 2m/70cm dual-band mobile. I'm looking for suggestions!

The location seems pretty logical, and is quite common in commercial/government use. Is it perfect? No, but if you choose an antenna that doesn't demand a good ground plane, it should work very well. Certainly cleaner than a mag mount with the coax coming in through a door, a capacitively-coupled glass-mount antenna, or a HT rubber duck!

I'll make a point of reporting back when I have mine installed. I'm trying to minimize the impact on the paint and body of the vehicle while maximizing the performance and durability of the installation.

-Peter

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ELMER
3 hours ago, N3IXY said:

My research has directed me towards buying a Comet 3/4" fender mount that is designed for the truck:

https://www.hamradio.com/detail.cfm?pid=H0-013680

-Peter

Hi Peter. I must be losing my eyesight. In the photo on HRO it looks like the mount is on the side of the box (which would actually be better than the fender). Am I seeing it wrong or is that what you meant?

H0-013680A.jpg

 

**EDIT** NEVER MIND... DUH DUH DUH.

I just realized where it's mounted. Losing it folks... I now realize I'm looking at the backside of the mirror so the mount is under the 'open' hood. Got it. Would be a good option, indeed. Not sure how 'pretty' it is, but in my book, signal first, beauty pageant second.

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Posted (edited)

Thanks for all the replies and the grand advice.  I don't know if I'll proceed or not though.  Looking at my truck, they just don't make anywhere to mount accessories under the dash anymore.  I sort of miss my old Chevy where the bottom of the dash was clear and you could mount your CB radio, trailer brake controller, and your 8-track just by drilling a couple holes under the dash and screwing the bracket on.  I thought about the under-the-seat option, but then I can't see all the purty colored lights on my screen and there's the dust/dirt problem under there.

Ford obviously didn't design their new trucks for under the dash accessories.  If I mount it on the drivers side it'll be in the way.  I got long legs.

I did find a steel plate that is intended for construction/emergency guys that allows them to mount their magnetic lights on the cab.  It mounts behind the cargo light, so it would offer bonding thru the cab, but the dang things are $200.  I'm more of a $59.00 guy.   🙂

F150.jpg

mount.JPG

mount2.JPG

Edited by KO4QDG
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  • 2 weeks later...

Parts for my install are being ordered today, for a trip departing in the next two weeks! Nothing like a deadline to motivate...

I expect to use the head separation feature in my Icom dual-band mobile. Not sure exactly where I'll locate that display, but I am not too proud to use velcro or dual-lock fasteners, as there aren't any obvious locations to permanently affix even this small unit. 

I'll make every effort to document the install, as there aren't too many how-tos for this model of truck.

I've decided to go with the Diamond NR-770HBNMO, as it is a simple design that should look good and wear well. I considered the Diamond SG7500, but they're essentially identical specifications (neither require a ground plane). The NR-770H one-piece whip will likely withstand more abuse than the multi-piece on the SG-7900.

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Posted (edited)

I stay away from velcro and use more traditional methods.  My dad is a truck driver and he used velco for all this gadets all over the dash.  Even the industrial stuff can't stand the summer heat and you end up with goo all over the dash and the weight of whatever your trying to fasten causes the adhesive to turn to goo and slide down.

I had a vinyl cover made for the center console storage so that my dogs toenails wouldn't scuff up the top.  He likes to sit up there when he rides with me.  The only way to attach it was with velcro around the edges.  It's turned to goo and is a gunky mess now after 3 years.

Velcro is awesome for lots of stuff, but the adhesive just can't stand up to the heat that builds up in a vehicle in the summer.  If you do decide to go with it, use the clear plastic velcro.  The adhesive on that has seemed to hold up better for me than the stuff on the black velcro.

Edited by KT4OBX
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ELMER
13 hours ago, KT4OBX said:

Even the industrial stuff can't stand the summer heat and you end up with goo all over the dash and the weight of whatever your trying to fasten causes the adhesive to turn to goo and slide down.

It's a conspiracy 🙄 Years ago, Goo Gone made a deal with 3M. Make your velcro adhesive max-disgusting and we'll swoop in. Obviously I jest, but yes Anthony, I agree, velcro goo is the worst. 

 

18 hours ago, N3IXY said:

I expect to use the head separation feature in my Icom dual-band mobile. Not sure exactly where I'll locate that display, but I am not too proud to use velcro or dual-lock fasteners, as there aren't any obvious locations to permanently affix even this small unit. 

I'll try to remember to take some photos today, but I have the heads of my Icom 5100 and Yaesu 891 mounted on the end of a flexible goose neck that attaches to the front left bolt of the passenger seat rail. Maria occasionally bumps into the setup but overall it's clean and holds well. Again, will try to post a photo or video later today.

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Since you stated that you have a mag mount quarter wave antenna, I assume we're not talking about 75 meters. If your truck has stake holes (if that's what they're called) in the bed wall, perhaps you could put some kind of pipe into the stake hole to get the base of the antenna level with the cab roof and then mount a J-pole antenna. Or you could mount your quarter wave with three radials.

 

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15 hours ago, WA2WMR said:

Since you stated that you have a mag mount quarter wave antenna, I assume we're not talking about 75 meters. If your truck has stake holes (if that's what they're called) in the bed wall, perhaps you could put some kind of pipe into the stake hole to get the base of the antenna level with the cab roof and then mount a J-pole antenna. Or you could mount your quarter wave with three radials.

 

Hey thats a plan!   I never thought of that.  My F150 has the plastic "plugs" that cover up those holes but I could pop one out.  I think I could have a small stainless plate about the same diameter as the mag antenna base welded to a short piece of square tubing, then bolt that into the stake hole from the inside for good bonding.

'Preciate the suggestion.

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