3rd Brake Light Antenna Mounts

[Alec]

Greetings...

Does anyone out there in GMRS land have any experience with 3rd brake light antenna mounts? 

Like these:  https://bulletproofdiesel.com/collections/antenna-mounts 

Do they leak?  Are they strong enough for a ~32" antenna?

I've been using a magnet mount on my GMC truck, running the coax out thru the rear sliding window, and placing the antenna on the roof of the cab just in front on the 3rd brake light.  From an RF signal perspective, it works just fine, but I would not mind transitioning to a more permanent antenna mount.  I like the idea of a no-drill solution and keeping the antenna's location more-or-less in the center of the ground plane.  That makes this antenna mounting option seem like an elegant solution even though it is a bit expensive.

Any feedback or personal experience is appreciated...

** UPDATED INFO: my truck has a retracting sun/moon roof which significantly complicates things as far as drilling and mounting anything in the roof of the cab more than a few inches forward of that 3rd tail-light because of the sliding glass, retraction motor, etc. of the sun/moon roof inside the roof of the cab.  Besides, I really don't want to drill into the roof of my cab!!!

Thanks

[WRUE951]

i bought one on ebay for half the cost from a guy that never installed it in a Ram truck he had.   It's a very nice quality setup up.  Realizing i still had to lower one side of my headliner to run the cable, i was upset that i even spent $200 for it.  Just drill tab a 3/4 inch hole and run the cable.  in my case getting the headliner partially down was most of the work.   There is no way i would spend $500 bucks for this..  Just my two cents, installed on a 2018 RAM 2500

[Socalgmrs]

Mounting it that way if it’s a ground plane antenna your missing 180 deg of ground plane.  But if you don’t mind only having 1/2 the ground plane go for it.   Or make the wise choice and drill a real nmo mount in the center of the roof.   
 

[WRYZ926]

Yes these mounts do work. But as mentioned, you still have to drop the headliner and you will lose have the ground plane. Losing half the ground plane is not a deal breaker as you will still get out but your antenna will be more directional to the front of the vehicle.

[Alec]

@WRUE951  Thanks for sharing your experience. I hear you.  I'm not thrilled about pulling the headliner either, as those things always turn out to be more difficult than we anticipate, but I figured that if I drilled a hole for a mount in the roof of the cab, I'd be going down that path anyway.  I agree the price is very steep for an antenna mount!   For my make/model/year truck the mount is no bargain @ $360 but if it avoids the potential for water leaks that can occur when you drill holes in the roof, (I've seen a lot of that with fleet vehicles) it is, from my perspective, worth the price.   Also, I'll be sure to check Ebay "IF" I end up going with this type of solution.

@Socalgmrs Thanks for your comment.  On my 2018 GMC Sierra pickup truck (w/ a 6' truck bed) the 3rd brake light is very close to being as centered, front-to-back and right-to-left, as you can get.    Thus, I don't believe this location sacrifices 180 degrees of ground plane as you suggest.  I'm not wanting to direct the radiating pattern in any specific direction.  If I'm not understanding your comment here, please explain...     

Thanks

[WRYZ926]

The bed will not act like a ground plane since it is lower than the cab of the truck.  The ground plane needs to be directly underneath the antenna. Sometimes even mounting an antenna to a luggage rack is not enough of a ground plane.

[WRUE951]

15 minutes ago, Alec said:

@WRUE951  Thanks for sharing your experience. I hear you.  I'm not thrilled about pulling the headliner either, as those things always turn out to be more difficult than we anticipate, but I figured that if I drilled a hole for a mount in the roof of the cab, I'd be going down that path anyway.  I agree the price is very steep for an antenna mount!   For my make/model/year truck the mount is no bargain @ $360 but if it avoids the potential for water leaks that can occur when you drill holes in the roof, (I've seen a lot of that with fleet vehicles) it is, from my perspective, worth the price.   Also, I'll be sure to check Ebay "IF" I end up going with this type of solution.

@Socalgmrs Thanks for your comment.  On my 2018 GMC Sierra pickup truck (w/ a 6' truck bed) the 3rd brake light is very close to being as centered, front-to-back and right-to-left, as you can get.    Thus, I don't believe this location sacrifices 180 degrees of ground plane as you suggest.  I'm not wanting to direct the radiating pattern in any specific direction.  If I'm not understanding your comment here, please explain...     

Thanks

Lowering the headliner even on one side was a pain. With the Ram you have to do it regardless if installing the 3rd brake light or drilling a hole to place an antenna.   (BTW, holes size is actually 5/8).  You won't have any water leaks if you get a good quality mount like a Midland, Larson, EM Wave (my favorite)  and install it right.  Google removing headliner on YouTube for your year/model Truck and see  what you are up against.  In my Ram doing one side would have provide more than enough room to drill and place a roof mount antenna.  When i found my brake light on Ebay i was searching 'Auto Roof Antenna Mounts'   

[tcp2525]

2 hours ago, Alec said:

Greetings...

Does anyone out there in GMRS land have any experience with 3rd brake light antenna mounts? 

Like these:  https://bulletproofdiesel.com/collections/antenna-mounts 

Do they leak?  Are they strong enough for a ~32" antenna?

I've been using a magnet mount on my GMC truck, running the coax out thru the rear sliding window, and placing the antenna on the roof of the cab just in front on the 3rd brake light.  From an RF signal perspective, it works just fine, but I would not mind transitioning to a more permanent antenna mount.  I like the idea of a no-drill solution and keeping the antenna's location more-or-less in the center of the ground plane.  That makes this antenna mounting option seem like an elegant solution even though it is a bit expensive.

Any feedback or personal experience is appreciated...

Thanks

Definitely neat gear for people that don't want to drill a hole in the roof. Just go through the pain of drilling the 3/4" hole in the roof and install a shiny new NMO mount and be done with it. And for added strengthening add a thin fender washer behind the mount to distribute the force if you hit low hanging branches or go into parking garages.

[WRYZ926]

Adding a fender washer to a NMO mount is a smart thing to do especially if your cab is aluminum.

I looked at the third brake light mounts when I had my 2020 Ranger but decided not to get one, mostly due to the price. Plus I would have had to run an even shorter antenna on the Ranger than what I run on the Escape.

[WRUE951]

52 minutes ago, tcp2525 said:

Definitely neat gear for people that don't want to drill a hole in the roof. Just go through the pain of drilling the 3/4" hole in the roof and install a shiny new NMO mount and be done with it. And for added strengthening add a thin fender washer behind the mount to distribute the force if you hit low hanging branches or go into parking garages.

i've seen NMO reinforcment plates but i think they are meant to be used under a fiberglass roof..  Think i seen them on DX but can't remember  

[Alec]

@WRYZ926 Great information here. Thanks!! 

I was aware that the different ground plane clearances of the various conductive sections of my truck (Hood, Cab & Bed) would alter the reflective properties of the RF counterpoise.  I was not aware that the vertical distance between the antenna on the cab and my truck bed, although more than a wavelength at GMRS frequencies, would effectively nullify all effectiveness of my truck bed as a ground plane!!   I'll certainly need to research and read up on that...  

My current magnet mount has been placed very near the 3rd tail-light location and suffers from the same ground plane issues and so far the performance has been acceptable to me.

I currently use a 5/8 wave GMRS antenna (although I'm not married to it - on rare occasions I swap it out for my 2M/70cm antenna) and at GMRS frequencies only about 15" of surface area is needed for an effective ground plane.  So, if RF optimization were my ONLY consideration, shifting that GMRS antenna forward a few inches from the rear of the cab would probably be close to as good as it is going to get for my vehicle...   

Many of the comments thus far suggest just biting the bullet and drilling that 5/8" hole in the roof of the cab of my truck and installing an NMO mount as the best approach.  I really do appreciate the feedback and comments!  But OUCH... I just have a real aversion to that, and most likely will never do so and would rather just live with a magnet mount.   Perhaps I should have mentioned in my OP that my truck has a retracting moon roof which significantly complicates things as far as drilling and mounting anything in the roof of the cab more than a few inches forward of that 3rd tail-light because of the sliding glass, retraction motor, etc. of the moon roof inside the roof of the cab.  And yes, the moon roof glass too impacts my ground plane to some degree.   If it's not one thing, it's another...

But still I'm seeking the convenience of some kind of permanent mount, even if not optimal from an RF perspective, which as stated in the OP, is why I'm looking at whatever alternate mounting solutions I can find. 

Hood/fender mounts are often a no-drill option but those too often force you to route the coax thru an RF noisy engine compartment.  They also tend to force you to mount them on either the right or left side of the vehicle which alters the radiating pattern to the sides, not to mention that you usually end up with the antenna being lower than the cab of the truck thus causing a certain amount of unwanted RF reflection if not some signal blockage.   

I conceded that there is no perfect solution, and things are never as simple as they may sound.  

So, while I'm not yet SOLD on this 3rd tail-light mount, and it is very expensive, thus far it seems to be a path to solve my specific problem.  This is why I'm looking for folks with first-hand experience specifically with these 3rd tail-light types of mounts, even though any and all feedback is much appreciated!

Thanks again...

[WSHH887]

I didn't want to drill any holes in my Tacoma.  I found a mount that attaches to the rear of the bed using existing bolts.  They make similar ones for other trucks.  Installation on mine was remove two bolts, then reinstall them with the mount in place.  I used an NMO mount on the bracket so I could easily remove the antenna to prevent theft.  Wiring ran underneath the edge of the bed and into the cab through a "overpressure vent" on the rear of the cab.  Zero holes drilled.

[WRYZ926]

I fully understand not wanting to drill holes into your vehicle. I have yet to get the courage up to drill my 2023 Ford Escape. Plus I don't feel confident removing the headliner with all of the curtain air bags.

Having a sun/moon roof definitely restricts where you can drill a hole for a NMO mount.

If you get acceptable results with a mag mount at the back edge of the cab then the third brake light mount will work for you. You will still have to deal with pulling at least part of the headliner down to run the coax though.

Only you can decide if the third brake light mount is worth the money, time, and effort. If it was me, I would look into a NMO mount since you have to remove the headliner for either one.

[WRUE951]

53 minutes ago, Alec said:

@WRYZ926 Great information here. Thanks!! 

   Perhaps I should have mentioned in my OP that my truck has a retracting moon roof which significantly complicates things as far as drilling and mounting anything in the roof

Well yea, that does change the picture..  i can imagine the moon roof will add more complications to the headliner removal.  You may have to drop the whole headliner because the moonroof will not let you tilt down the headline form one side.  You also dont want to route the coax along either outer edges of the headline because that will impede the air bag function.  There are front fender mount options that mount under the hood and wrap around the hood by  the cowl area.  I had a jeep mount that worked well for that.  The Mag mount works well too until you get into a good rain storm..  Don't ask me how i know that one.   Good Luck.  defiantly visit YouTube and see if you can get any ideas on difficulty for your headliner.  It could be easier then you think and vis a versa.   Good luck  

[gortex2]

I tried one of these on a SAR members vehicle, 2021 3500HD DEnali with the sliding roof as yours. It was on a trunked system and on the system with a 1/4 wave worked ok. Simplex was misserable. Since then I dropped 2 NMO mounts in the roof and that mount was given away. There is plenty enough room for a NMO on each side. He runs a 1/4 wave VHF and UHF. At times he does swap out to the Larsen NMO puck on UHF but 90% of the time the 1/4 wave is on the truck. 

[73blazer]

Ouch, 359.65?! 

[WSEZ864]

I considered buy one of those mounts for my 2020 F-150. It too had a sunroof that precluded installing a regular NMO mount.

I installed a "Back Rack", which I use to haul canoes, ladders and lumber anyway, and mounted two antennas on the vertical bars at the sides. VHF on one side, UHF on the other. The Back Rack is bonded to the truck bed and the bed is bonded to the cab. I brought the cables in under the rear seat, under the carpet to the front seats, where my radios are hung. Works 'OK', but not quite a well as the NMO in the center of the roof on my last truck.

[WRUE951]

2 minutes ago, WSEZ864 said:

I considered buy one of those mounts for my 2020 F-150. It too had a sunroof that precluded installing a regular NMO mount.

I installed a "Back Rack", which I use to haul canoes, ladders and lumber anyway, and mounted two antennas on the vertical bars at the sides. VHF on one side, UHF on the other. The Back Rack is bonded to the truck bed and the bed is bonded to the cab. I brought the cables in under the rear seat, under the carpet to the front seats, where my radios are hung. Works 'OK', but not quite a well as the NMO in the center of the roof on my last truck.

And you probably paid less for the rack..  I have one of the 3rd brake light antenna mounts and knowing what i know now, i wouldn't pay $150 bucks.  It is a quality milled piece of metal with a decent coax but it is a waste of money at the end of the da.   I like the rack idea.  Never thought of that.    

[tcp2525]

22 minutes ago, WSEZ864 said:

I considered buy one of those mounts for my 2020 F-150. It too had a sunroof that precluded installing a regular NMO mount.

I installed a "Back Rack", which I use to haul canoes, ladders and lumber anyway, and mounted two antennas on the vertical bars at the sides. VHF on one side, UHF on the other. The Back Rack is bonded to the truck bed and the bed is bonded to the cab. I brought the cables in under the rear seat, under the carpet to the front seats, where my radios are hung. Works 'OK', but not quite a well as the NMO in the center of the roof on my last truck.

I too have an F150 and the power sunroof is not an issue. Plenty of room for an NMO mount.

[WSEZ864]

2 hours ago, tcp2525 said:

I too have an F150 and the power sunroof is not an issue. Plenty of room for an NMO mount.

Maybe so, but it didn't look like it on mine. Mine has the retractable cover inside, side-curtain air bags, plus the regular glass window and by the time I avoided all of those items, I decided it wasn't worth trying to squeeze in there. The truck body is also aluminum and rather soft, so I was already on the edge of not using an NMO on the roof.

https://www.ar15.com/forums/outdoors/Installing-Antennas-and-Radio-on-2020-F-150-Crew-w-Sunroof-Now-with-Moar-BackRack-/22-705121/

[WRCR724]

4 hours ago, 73blazer said:

Ouch, 359.65?! 

They're very proud of those mounts. I know know someone who has one and it's very nice, but I don't know if I could bring myself to purchase one. 

[WRUU653]

This (A-Pillar Antenna Mount) is another option to try that won’t break the bank. I have a version of this on my Tacoma and despite what some might think it works for me. I used to have a Midland MXTA 26 which worked great, now I’m using a Comet SBB5 (ham) also good results.  Sure it might work better in the center of the roof… until it gets snapped off with a kayak. Sometimes there are compromises and good enough is just that.  
 

[Alec]

@WSEZ864 Thanks for the suggestion about the back rack, and for the photo!  Very helpful.  That is certainly an interesting option worthy of consideration. 

@WRUU653 Thanks for the A-Pillar suggestion.  I do understand compromises... 

Cost isn't a primary consideration for me, but even so the 3rd tail-light mount is in itself sort of a compromise, rather than following the recommendation of the "drill-baby-drill" enthusiasts who advocate for just installing that NMO mount.  While an NMO mount installed dead center of the roof of my truck cab might be the best solution for RF purposes, that isn't necessarily the best solution for my purposes.

I've been browsing YouTube videos about removing the headliner as was suggested by @WRUE951 and unless you are someone who does that sort of thing all the time, it appears like it could potentially be a PITA that is not without its own considerations and complications.   

In the process, I've also stumbled across a great many videos regarding replacing or fixing a 3rd taillight on these trucks.  Some replace it for the purpose of a cargo/5th wheel bed camera, others for brighter or flashing LED lights etc.  Many people with many different reasons. However, there are also folks that speak of damaged headliners as a result of leaks from a worn 3rd taillight lens gasket. Many suggest that it is not "IF" it will eventually leak, but rather "WHEN" it will leak, and they advocate replacing the gasket and resealing these 3rd taillight assemblies with silicone as a preventative measure.  Something to think about...

Interestingly enough that gets me back to my original post about this type of antenna mount where I asked those with direct experience using these devices: "Do they leak?"  I'm thinking of an antenna being pushed by wind or by hitting trees, etc. and wonder how that might contribute to breaking or otherwise compromising that watertight seal around the mount?  IOW, if these 3rd taillight assemblies are prone to leaking, maybe introducing an antenna mount there would be inclined to make matters worse.   

Absolutely nothing is without compromise!!

Again, thanks for the comments and feedback on the topic.

[dosw]

On 4/14/2025 at 4:38 PM, Alec said:

 On my 2018 GMC Sierra pickup truck (w/ a 6' truck bed) the 3rd brake light is very close to being as centered, front-to-back and right-to-left, as you can get.    Thus, I don't believe this location sacrifices 180 degrees of ground plane as you suggest.  I'm not wanting to direct the radiating pattern in any specific direction.  If I'm not understanding your comment here, please explain...     

Thanks

You'll maybe need to show a picture demonstrating how an NMO mount on top of the 3rd brake light has a full 360 degree ground plane. Three or four feet below inside the truck bed is not acting as a ground plane. So if that's what you're expecting to consider as your ground plane, no photo needed. It's not doing what you think. Now, it may *work* to have an antenna mounted there. You'll be able to transmit and receive. But your SWR will be a little high, and your propagation in the aft 180 degrees will be relatively lousy.

[dosw]

3 hours ago, Alec said:

@WSEZ864 Thanks for the suggestion about the back rack, and for the photo!  Very helpful.  That is certainly an interesting option worthy of consideration. 

@WRUU653 Thanks for the A-Pillar suggestion.  I do understand compromises... 

Cost isn't a primary consideration for me, but even so the 3rd tail-light mount is in itself sort of a compromise, rather than following the recommendation of the "drill-baby-drill" enthusiasts who advocate for just installing that NMO mount.  While an NMO mount installed dead center of the roof of my truck cab might be the best solution for RF purposes, that isn't necessarily the best solution for my purposes.

I've been browsing YouTube videos about removing the headliner as was suggested by @WRUE951 and unless you are someone who does that sort of thing all the time, it appears like it could potentially be a PITA that is not without its own considerations and complications.   

In the process, I've also stumbled across a great many videos regarding replacing or fixing a 3rd taillight on these trucks.  Some replace it for the purpose of a cargo/5th wheel bed camera, others for brighter or flashing LED lights etc.  Many people with many different reasons. However, there are also folks that speak of damaged headliners as a result of leaks from a worn 3rd taillight lens gasket. Many suggest that it is not "IF" it will eventually leak, but rather "WHEN" it will leak, and they advocate replacing the gasket and resealing these 3rd taillight assemblies with silicone as a preventative measure.  Something to think about...

Interestingly enough that gets me back to my original post about this type of antenna mount where I asked those with direct experience using these devices: "Do they leak?"  I'm thinking of an antenna being pushed by wind or by hitting trees, etc. and wonder how that might contribute to breaking or otherwise compromising that watertight seal around the mount?  IOW, if these 3rd taillight assemblies are prone to leaking, maybe introducing an antenna mount there would be inclined to make matters worse.   

Absolutely nothing is without compromise!!

Again, thanks for the comments and feedback on the topic.

This is how this thread has gone:

 

OP: Has anyone tried these?

Others: Those won't have a very good ground plane, and that will hamper your signal propagation.

OP: But this is what I want to do.

Others: *shrug* then why did you ask?