NMO truck bed install questions

KC9LQV · #1 (**permalink**) 07-22-2010, 11:03 AM

I have some questions concerning an "external" NMO mount that I want to put on the lip of the bed of my truck.

I see a variety of solutions ... from a simple angle iron with a hole in it, to more elaborate mounts costing up to $70.

My concern is that with a simple angle bar, the NMO mount is exposed to the elements from the underneath. Is this a concern? Is there an effective way to seal it, if needed?

At the moment, I'm giving this mount strong consideration:

Angle Bracket Mount Stainless Steel NMO

The price certainly seems right, and a bit more protected than the plain angle bar. Anyone tried this mount or something similar?

If the lip of the truck bed is wide enough, is there any reason not to simply drill the NMO mount right into the lip and install it directly?

I'd want to put the antenna as far away from the truck cab as possible, correct?

Would two identical 5/8 160mHz antennas on opposite sides of the truck bed be far enough apart? I had two mounted on the roof of the truck and they rendered each other almost deaf when in each other's shadow.

Thanks in advance.

jim202 · #2 (**permalink**) 07-22-2010, 12:03 PM

Quote:

Originally Posted by KC9LQV

I have some questions concerning an "external" NMO mount that I want to put on the lip of the bed of my truck.

I see a variety of solutions ... from a simple angle iron with a hole in it, to more elaborate mounts costing up to $70.

My concern is that with a simple angle bar, the NMO mount is exposed to the elements from the underneath. Is this a concern? Is there an effective way to seal it, if needed?

At the moment, I'm giving this mount strong consideration:

Angle Bracket Mount Stainless Steel NMO

The price certainly seems right, and a bit more protected than the plain angle bar. Anyone tried this mount or something similar?

If the lip of the truck bed is wide enough, is there any reason not to simply drill the NMO mount right into the lip and install it directly?

I'd want to put the antenna as far away from the truck cab as possible, correct?

Would two identical 5/8 160mHz antennas on opposite sides of the truck bed be far enough apart? I had two mounted on the roof of the truck and they rendered each other almost deaf when in each other's shadow.

Thanks in advance.

I am not sure where your coming from in saying that 2 VHF antennas on your roof rendered them
deaf. I have for years run 2 antennas on the roof of my truck with no problems. Sure if you talk on
one VHF radio, it will cause the other to go deaf while your talking. That is just the physics of the
beast. Live with it.

As for mounting an NMO mount on the lip of the bed, the functionality of the antenna there will
depend on what frequency band your going to use the antenna on. Remember that most of the
mobile antennas on the market are looking for a ground plane reflector under them. The lip of
the pickup bed doesn't have much metal around it to act as the ground plane. As such the
performance of most antennas you mount there will be marginal.

Not sure about the weather sealing choices. I generally use an RTV silicon adhesive to seal
everything up with. Just let it cure before trying to do any transmitting to that antenna. About
24 hours should do the trick.

DDan · #3 (**permalink**) 07-22-2010, 1:19 PM

Ditto what Jim said about the groundplane. With a practically non-existent ground plane, you will have a poor performing antenna.

KC9LQV · #4 (**permalink**) 07-22-2010, 1:50 PM

I guess I'm confused about the type of antenna used with these mounts. All of the major antenna manufacturers (Larsen, Diamond, etc.) sell clamp-on and trunk-lip mounts for their whip antennas just like the one I use (Larsen NMO150B).

I understood that there would be some amount of gain loss from losing the ground plane, but in my case even a unity antenna on the bed is better than a deaf one on the roof.

Or are you gentlemen suggesting that the loss of performance would be even worse than that?

If the standard NMO coil-and-whip antennas are not the ones intended for those mounts, which ones are?

rectanglehead808 · #5 (**permalink**) 07-22-2010, 3:46 PM

I use the stake holes in my truck bed to mount my antennas and they work fine.
I have a 4' firestik 2m for my vhf and it does the job just fine. It withstands low ceiling parking garages and driving offroad.

antenna: FireStik 2M-4 4' 2 Meter BLACK Antenna **NEW** - eBay (item 200292283975 end time Aug-18-10 22:55:33 PDT)

mount: Firestik Pick up Stake hole mount with 18' Coax MK-294R - eBay (item 360200112807 end time Aug-16-10 11:37:55 PDT)

W2NJS · #6 (**permalink**) 07-22-2010, 6:55 PM

If you put the NMO on the bed rail you'll never know how flat the SWR is, or is not, until you actually try the setup. Easiest way would be to set it up with longer-than-necessary quarter wave NMO whips, read the SWR, then start cutting. You might be able to get it down to less than 2:1 just using the bed rail as the ground. Again, you never with situations like this until you actually try it.

The photo on the catalog sheet you listed appears to have an enclosed section where the coax connects to the underside of the actual NMO mounting. I'd still stick some RTV on it just for insurance against the weather.

tcm4368 · #7 (**permalink**) 07-28-2010, 7:23 PM

I did just what you are wanting to do on three of my trucks and it worked ok....yes roof would have been better, but I had clearance issues with the garage. I could hit my repeater from 30 mi away without too much trouble. I'll try and post a pix. Charcoal truck is the 2006, and when I upgraded to the 2008 I installed a rack on the bed to mount antennas on, that way no holes in the roof.

DSallee · #8 (**permalink**) 01-06-2013, 5:07 PM

I know this is an old post and sorry for bringing it back to the top... I'm wondering if anyone can tell me who makes the bed light bar in the last two pics?? I just got a 2010 F150 and looking for ways to mount my antenna without drilling holes in the cab... I really like this bar and think it would work good in my situation...

Thanks
Dave

wheelerg · #9 (**permalink**) 01-08-2013, 6:23 AM

That is a nice bar, not too big and gawdy, yet serves a good purpose, i just wonder how it mounts to the bed of the truck? i am sure big bolts are the method.

tcm4368 · #10 (**permalink**) 01-12-2013, 4:25 PM

I was just browsing this topic and didn't realize it was that old either untill I saw my pictures! The rack was made by Go Rhino Products and is called the Thunder series if I remember correctly. I ordered it new from Summit Racing Equipment., and if memory serves me right it was under $200 in 2008. When I traded for the F350 diesel, (see F350 Super Duty install on this site) We had to modify the rack to fit, as the cab is taller on the Super Duty's over the F1's. It turned out well and still serves the intended purpose.

Trent.

KC0CSE · #11 (**permalink**) 01-12-2013, 6:32 PM

Quote:

Originally Posted by tcm4368

I was just browsing this topic and didn't realize it was that old either untill I saw my pictures! The rack was made by Go Rhino Products and is called the Thunder series if I remember correctly. I ordered it new from Summit Racing Equipment., and if memory serves me right it was under $200 in 2008. When I traded for the F350 diesel, (see F350 Super Duty install on this site) We had to modify the rack to fit, as the cab is taller on the Super Duty's over the F1's. It turned out well and still serves the intended purpose.

Trent.

wow I really like your set-up.....I need to get one of those.....have a Ford F-150 1997....hope I can find one to fit...might be to old...thanks for the pictures....Mike

mgolden2 · #12 (**permalink**) 01-24-2013, 3:53 AM

tcm4368 - Could you post some pics of the inside of your truck so we can see what all those antennas go to? (and the outside of the truck looks awesome too!)

KC9LQV - when you figure out a mounting method could you post pictures as well please?

tcm4368 · #13 (**permalink**) 01-26-2013, 8:43 AM

Check out "F350 Super Duty install" on this site for detailed pictures. I am running a Motorola UHF business band, Cobra CB, and Motorola cellular.

Might also be interested in out other trucks over the years.

"2006 Ford F150" which is the silver truck above.
"2008 Ford F150" which was my whate sand truck I had before this F350.
"1995 Foed F150" is my "beater" daily driver
"2008+ Kenworth"

These are all posted in the "install or pictures of your shack" section of this site.

Thanks for the interest.

Trent

Drachen_Fire · #14 (**permalink**) 02-28-2013, 10:50 AM

The lightbar is a very old model, which I think may still be in new production. It's the Federal Signal Highlighter. A direct knockoff of this bar is sold in Pep Boys under the brand name TurboBeam.

For my last couple of vehicles, and my current ambulances and wheelchair vans, I use Larsen L-brackets and NMO mounts, and minor SWR issues aside, they work wonderfully. One of those previous vehicles was a Ford Ranger. I had a 5/8 wave UHF antenna on the driver's side of the bed, a 5/8 wave VHF antenna on the passenger's side, and a base-loaded low band whip on the center roll bar, all on L bracket NMO mounts, and they performed fine.

As far as corrosion issues, there's nothing to worry about. The mounts are either made of hard brass, or are plated in chrome, or are made of stainless (rare). They don't really corrode. I'll put it to you this way. I've been using the same NMO mounts, on different vehicles, all bracket mounted, for 4 years, through salt-laden Pennsylvania winters, and they look new.