Drilling a hole in the roof... NMO mount for GMRS use.

After a GRMS thread showed up in the forums recently I decided to move forward with my plans to mount a Midland MXT275 in the truck. The primary purpose will be talking to others while on the road. We generally use our Garmin Rino 650 for communication on the trail, hunting, skiing, or over the road. I also have a Motorola M1225 mounted on the Polaris Ranger for when we are out hunting and trail riding. To this point myself and other friends and family are heavily invested in GMRS.

The problem of using a handheld radio inside a truck or car you loose a good amount of range. We would often get enough distance or terrain between us that we couldn't always relay that we were getting off at the next exit or that someone was having issues. Sometimes we could use cellphones, other times there wasn't signal.

Additionally handhelds can only put out 5 watts of power where a mounted mobile can output up to 50 watts. While more wattage doesn't always mean more range, it usually means that your message will come in more clear when you are on the edge of your range. On top of range a mobile works with an external antenna which often promotes range over pure power. Meaning both radios at 5 watts the one with the better antenna will win. It also allows you to pick up handhelds better. Since adding a mobile to my UTV the range I get between a handheld and handled vs handheld and mobile are noticeably different.

What I needed for this project...

The radio
Midland MXT275, purchased directly from Midland.

Other parts purchased.
NMO mount Larsen 3/4"

$24 Larsen - 3/4" Hole Mount Antenna with 0-6 GHz Frequency No Connector

https://www.amazon.com/gp/product/B007JSEBJM/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1
UHF PL-259 crimp connector

$13 RFIOTASY Pack of 5 UHF PL-259 PL259 Male-Plug Crimp Connector Adapter Connector for RG58/U LMR195 (UHF Male Crimp RG58)

https://www.amazon.com/gp/product/B07K23PFX9/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1
Crimping tool
https://www.amazon.com/gp/product/B00N3PDPYC/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1
Laird HS34 3/4" hole saw

$99 Laird HS34-3/4" Hole Saw - Allows for safe, accurate drilling of 3/4" holes into vehicle surface.

https://www.amazon.com/gp/product/B01NAXO0N7/ref=ppx_yo_dt_b_asin_title_o02_s01?ie=UTF8&psc=1
Tram 1290 rain cap

$9 Tram 1290 NMO Rain Cap Black Heavy-Duty Plastic with O Ring Gasket for Secure Weather Protection

https://www.amazon.com/gp/product/B00474A1M2/ref=ppx_yo_dt_b_asin_title_o00_s01?ie=UTF8&psc=1

For now I'm stealing the low profile antenna I have from the Ranger. I will end up getting a dedicated low profile and full antenna for the truck.

$23 Browning BR2445 450MHZ–465MHz Pretuned Low-Profile UHF Band NMO Antenna, 3 1/4" Tall

https://www.amazon.com/dp/B00DIH6HRC

Also purchased a center console organizer to keep things off the radio as they warm up when you transmit and I don't want the thing to overheat. Plus the box of a center console really needs organization.

Additionally, I used a few metric sockets to remove the trim panels and the rear seats. A wire cutter, coax stripper, soldering iron, and heat gun when putting the end on the cable. Zip ties for routing the cable down the rear pillar.

 

I started the install by removing the front and rear door sill trim that covers the ends of the middle pillar bottom trim. Also pulled off the cover for the bottom bolt of the drivers seat belt.



Next remove the bolt for the drivers seat belt that was just uncovered. Then you can pull the bottom pillar trim off.


At this point I did pull off the top portion of the middle pillar, but after seeing the routing and design of the side curtain airbags I decided to look at the rear pillar to route the wire. So out came the rear seats and I pulled off the rear trim. Near the same process as the front. There is a seat belt bolt at the bottom. A bolt for the top trim that is exposed once you remove the bottom trim and another under the side curtain badge towards the top. You will then see some wire that runs to the rear brake light.

Unfortunately I had to charge my phone so the pictures are a little light for the next part. I popped out the rear dome light to have access to the roof and be able to plan out where to drill the hole. This also gave me access to use a push pole to run a pull line from the back corner of the headliner to the dome light so I could pull the coax down the headliner.

As for drilling the hole I measured things at least 3 times then another 3 to be sure I didn't mess up. I used masking tape to cover the paint while drilling and mark where to drill. I measured from edge for the rear brake right to 25" and then found center side to side. I used a center punch to mark the hole and then drilled a pilot hole to check the location. I took a deep breath and checked that the bit came though where I expected. It did, so I grabbed the other drill and continued drilling with the hole saw. Before drilling I sprayed the surface with some metal lubricant. When drilling I ran it very slow and let the bit do the work. One thing I wish I would have done is put something between the metal and headliner to push the insulation down. Didn't do any damage, but did pull on it a little.

After drilling the hole I took my rotary tool with a sanding bit to get down to the bare metal for ground the NMO. Next was pulling the coax, I taped the coax to the pull wire that placed earlier. I pulled all the wire down the corner of the headliner and routed it down with the other wires while securing it to the other wire group. Then went back up top to secure the NMO mount using a needle-nose and adjustable wrench.







From here I cleaned out the center console and determined where to mount the radio so the handset wire could be routed through the wire grove of the console. Once this was determined I could find a spot to pull the coax. Once I determined the spot I wanted to use I slowly drilled a hole because I couldn't determine if anything was behind it. The I used a few zip ties taped together as my pull cord for this run. I ran it down the split between the carpet under the front seat and over the vent.


Then I cut a fresh end on the coax before installing the PL-259 connector. I did solder the end, but didn't take a picture afterwards.

Next came mounting the radio. For now I plan on just using the cig outlet, and from testing it doesn't appear to have any noise on the receiving end. Eventually I will pull from the battery.



Here is the final product.

 

Reserved

 

This should be good!

 

Updated, If anyone has recommendations on a full GMRS antenna please let me know.

 

I absolutely commend you for drilling a hole in your roof. For an antenna mount

I can not get up the balls to do so
Even though i seriously want to place a low pro antenna for my HAM radio and CB up there

 

It's not too bad. I was just worried until I saw where the pilot hole came out where I wanted it.

 

You my friend have some stones to drill a hole in the roof of a 50k truck for an antenna! It took me 2 days and a case of beer to get mine big enough to cut the carpet and foam out of the rear floor for the ESP storage mod...kudos to you!

 

As someone who has drilled holes in over 20,000 trucks over the years, I can tell you it gets easier and easier. Lol. On the Tundra, the quickest route is pop out dome light, use a long Phillips screwdriver tilted up and toward rear of cab. Center by site and tap it lightly up. It will put a dimple in the cab and then measure on top, side to side for center. Drop loose the door sill rubber (on passenger side) and push a fish through to opening of dome light. Tape coax to fish. Pull through. Loosen the remaining rubber down the “A” pillar and down the edge of dash. Route coax down the “A” pillar, through end of dash and under the of passenger foot area carpet to the center. With the armrest open the console cover can be removed and coax can easily be routed through. It can all be done, hole drilled, antenna mounted, coax ran and terminated in less than 10 minutes. Removing the paint on the underside I’d not required as the cutting edge of the hole makes connection as well as the cleats on the mount will dig in, plus, condensation can gather on it and cause rust. Laird makes a good hole saw but watch the tips on the blade, they break off (also the blade is not one continuous piece and can pull out if it catches) and will cause it to want to catch or “walk” a little. I’ve drilled holes in $400k+ trucks, ain’t nothin but a thang. Lol. However, Toyota does build a “tight” interior compared to some. Enjoy!

 

Yeah I couldn't do it. I got a bed rail stake mount for my 2m/70cm HAM antenna. I like the idea of low profile roof mount but it's a truck ... I don't want to drill into it and a half wave 2m antenna doesn't look weird on a full size truck if done correctly. Just remember to remove it before the carwash.

 

There are holes on the bottom of the truck from the factory you could have routed an antenna cable then mounted the antenna to the bed. Would have saved you from drilling through your roof.

 

I agree with chasenicholas9. No holes in the roof. GMRS frequencies are high enough that placing the antenna on the bed edge (using one of the post holes and a mount for it) will give you a clean install. Only problem is you want your feed line to be as short as possible (RG58 is pretty lossy at those frequencies), so try to keep that feed short.

 

There is a loss, it can be a considerable one, with mounting an antenna to the bed. Through hole roof mount will give you a 0.0db loss, on the bed can almost be as much loss as the antenna has gain.

 

That's the main reason I did this, best performance possible.

 

I have a cell phone, Sat communicator (Garmin) and Satellite phone. I'm good on drilling holes in my roof. Cool project though

 

What sat phone. I have the InReach as well. Always wanted a sat phone.

 

@KevinK care to comment on antenna placement and possible cons???

 

I had a Globalstar for years for dive trips to lesser developed parts of the Caribbean. It was pretty good there but in the mountainous geography of West Virginia it was very limited unless on top of a mountain or in the wide open somewhere.

 

Hopefully these images help illustrate the reason I drilled and mounted an antenna on the roof.

 

hahah! I NMO mounted through our roof a few years ago - twice. wrote it up in our build someplace. There's a couple entries near the top of our table of contents: https://www.tundras.com/threads/komodo-my-wifes-daily-driver-and-high-speed-overland-rig.16989/

Lisa now has a little R2-D2 looking droid thing in the roof of her truck to plug one of the holes where I ripped it out from pulling into the garage without taking the full antenna down. There's also a defunct NMO up there we never use anymore since we switched to hood mount with a mag.






Now we just rock out like a unicorn... The best part is we no longer have to flip the antenna down for low hanging branches on the trail (I got tired of that real quick), parking garages, drive thru or anything. We drove under railroad tracks in the middle of the desert like this and there was only about 7 inches clearance above the roof itself.





I like that low profile antenna, what's the gain like on that vs a 'real' dual bander? Or are you only using this for the GMRS signals?

 

OP, Let me translate that long-winded, veiled self promoting post for you: Kevin ripped a hole in his roof, twice, because he hard mounted an NMO antenna to his roof.

The rest of his post is him trying to talk you into mounting your antenna in the middle of your hood like someone who chews crayons. I'll drink beer with Kevin any day, but I've yet to see him convince anyone to mount it on their hood LOL

I would suggest you get an antenna with a spring, although that might not be enough to prevent you from bending the sheet metal.

 

We appreciate your translation services.

Also, unicorns are fuckin majestic.

 

Thanks for that info. It's good to know. I don't foresee an issue once

$90 Larsen 450-470 MHz Mirage Low Visibility Transit Style Antenna - Black

this low-profile Larsen antenna get delivered. It will be installed for 99% of driving. The larger antenna will be used mostly on open roads and highways when I need the extended range for car to car comms. I do like the idea of using a spring antenna and was something I was looking into. Also was thinking about installing a thicker piece of steel between the roof and nmo mount to give it some more rigidity.

 

I might go back to a roof mounted antenna if there's a low profile like this that is dual band and works on 2m and 70cm.

Know if such an animal exists of the top of your head?

 

I don't know off hand.

 

I dont see how you're gonna get a 2m antenna like that. the physics dont work

 

They come in quarter and 5/8 and half wave lengths. So a quarter wave 2m is about 20 inches long. But then it has to get packaged inside a cylinder as a coil or whatever.

Apparently low profile and dual band 2m/70cm don't really go together because of the compromise of length and then packaging it. They exist, but performance sucks.

Alex, do we ever really use the UHF on our dual bands? I think we usually just run in the VHF end. I might get this one I found for 2m and put it back on the roof. Should sit lower than the light bar.

https://www.arcantenna.com/m2m-ante...0-300-mhz-black-low-profile-omni-antenna.html

 

I got dual band in case someone has a GMRS

The theory is that 10cm is better in the forest and city. but in reality I doubt we would notice the difference

I carry 3 different antenna now haha two are dual band, 18" and 40" and I also picked up a 57" 2m thinking it would improve reception, but it didnt. I have a feeling my mag mount is the weak point.

Doesnt matter though, I get enough range even with the 18"

 

Oh yeah, I forgot about the GMRS. And you're right, probably splitting hairs for our use case on the antennas. I might grab that low profile VHF one and give it a shot though. Mount it dead center on the hood and be a rhinoceros instead of a unicorn.