GMRS / CB antenna locations - near A pillar or mid point on hood

[chorky]

As title suggests. I have come to the conclusion that fabricating brackets for the antennas to go on the roof just won't be any time soon. So, the typical A pillar or hood mount it will be as much as I hate it.

For those who have had antennas mounted in both locations, have you noticed one that works better than the other? Seems the further toward the front it would be better to avoid interference form the A pillar steel (and be further away from your body for exposure).

Also curious if anyone has suggestions for no ground pane antennas? I can't seem to find any that specify it lately for some reason.... Websites I have looked at just don't seem to specify it under the product if it is a no ground pane antenna or not.

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[ThrillSeekr]

I ordered from FabTech Motor Sports for my HAM radio setup. No concerns with interference or exposure with (2) 50W radios mounted. Mounts up super easy and no issues with cable routing via the windshield. I wanted a heavier duty mount since I have 40" antennas.

Links:
The Cowl Mount Brackets

The Add On Antenna Mount

 

[chorky]

I ordered from FabTech Motor Sports for my HAM radio setup. No concerns with interference or exposure with (2) 50W radios mounted. Mounts up super easy and no issues with cable routing via the windshield. I wanted a heavier duty mount since I have 40" antennas.

Links:
The Cowl Mount Brackets

The Add On Antenna Mount

No concerns for exposure? Thats a lot of power within a couple feet of you...

Are they NGP antennas though? Your pic is similar to one of my mounting option thoughts.

 

[ThrillSeekr]

The antenna I use does not require a ground plane:

Diamond SG7500A

I turn my transmit power down, and, monitor aircraft, local PD, or HAM freqs a whole lot more than I transmit.

 

[ParatusExpeditions]

I fabricated a mount because I wanted to keep the Jeep garage compatible. My SWR on my install is 1.6 and although not perfect (could be for any other reasons than location) I can communicate very clearly on GMRS, connected to a repeater 8mi away from where this picture was taken without issue etc.

the antenna is vertical but slightly canted to the left, about 2 degrees. This is due to the bumper and I couldn’t correct it through designing the mount in such a way it’s straight with the fabrication process I went with. Overall under 5 degree won’t hurt much, I’d say it could even be somewhat beneficial reducing the bounce/obstruction against the car for people behind. But this is untested theory obviously.

the picture is a bit old, I’m on 37”s now and still clears the garage entrance as the antenna isn’t higher than the car while still being a 6db antenna.

 

[PJZ]

I used a Cool Tech mount for my GMRS and painted it black. It's ok for lighter antennas.
https://www.cooltechllc.com/2018-jeep-wrangler-jl/139-gladiatorwrangler-front-antenna-mount.html

 

[Radio Guy]

Unless you have some cowl mounted lights that block using the hood, a trunk lip mount on the hood near the hinges will put the antenna at top of hood level and will give ok overall performance. The mounts that go between the hood and body put the base of the antenna or an entire short "pud" style antenna completely below hood level.

Here is one of my two trunk lip NMO mounts on the hood and there is one on each side.

 

[chorky]

I fabricated a mount because I wanted to keep the Jeep garage compatible. My SWR on my install is 1.6 and although not perfect (could be for any other reasons than location) I can communicate very clearly on GMRS, connected to a repeater 8mi away from where this picture was taken without issue etc.

the antenna is vertical but slightly canted to the left, about 2 degrees. This is due to the bumper and I couldn’t correct it through designing the mount in such a way it’s straight with the fabrication process I went with. Overall under 5 degree won’t hurt much, I’d say it could even be somewhat beneficial reducing the bounce/obstruction against the car for people behind. But this is untested theory obviously.

the picture is a bit old, I’m on 37”s now and still clears the garage entrance as the antenna isn’t higher than the car while still being a 6db antenna.

Aussie style! How is your range to the rear of the vehicle though? I would prefer a 0db gain, or maybe 1 at the most. The more DB gain the less it works well in hilly/mountainous terrain - which I have a lot of. It seems difficult to find a 0 or low db gain antenna for some reason. Even the ones that come with radios (the mag mount's) seem to have at least 3db gain. So that will be another struggle, finding the right antenna.

Unless you have some cowl mounted lights that block using the hood, a trunk lip mount on the hood near the hinges will put the antenna at top of hood level and will give ok overall performance. The mounts that go between the hood and body put the base of the antenna or an entire short "pud" style antenna completely below hood level.

Here is one of my two trunk lip NMO mounts on the hood and there is one on each side.

Yeah I had thought about that, but I do plan on cowl lights. Maybe the MOPAR brackets, maybe aftermarket. However, that means the radio could be attached to those brackets as well, so that the base would be above hood level. The downside to that is then the radio is very close to me (one on driver, one on passenger side). I dont know how comfortable I am with that considering 1) proximity to my body (I have already had enough radio frequency exposure in my life), and 2) how it will impact rearward transmit distance (I dont have a computer model to test and seee what it will actually look like). I would much prefer a 0db gain antenna due to mountainous terrain in my area - much more important to me that long distance on the flats. I guess up to 3db would be ok since that seems to be the 'standard' for antennas these days anyway.

 

[ParatusExpeditions]

I have a 50W so haven’t heard any complains. This is a good consideration , but GMRS itself isn’t that good and designed for mountains separation etc. If I stick to what it’s good for: direct line of sight I get a lot of “fars” and I’ve been told I sound really clear. The antenna I a Nagoya 770g nmo mount if I recall correctly.

 

[chorky]

Ok so I'm going to open this back up with a couple more questions. Not sure if DaveInDenver from expo is here but a few more details so maybe it will help encourage discussion.


CB Talk
CB radio of choice (not yet ordered) - Uniden CMX760 https://www.rightchannelradios.com/products/uniden-off-road-cmx760

Now, I know there's a lot of talk about cowl mounts and hood lip mounts. But if a guy were to consider a mid load antenna (options below), would it sway a direction to a particular mount type?

https://www.rightchannelradios.com/products/cobra-high-gear-trucker-cb-antenna
https://www.rightchannelradios.com/products/stryker-center-load-antenna-1
https://www.rightchannelradios.com/products/president-texas-cb-antenna

Now to throw another curve ball... I so happen to have TWO 102" whips in the basement. I could get a ball mount and put one on the side of the canopy. I do have a 102 on my TJ, and it works excellent, except for hitting a lot of things. Now the question though, is I am not going to run SSB with the CMX760 - so would a 102 really benefit? I have been able to get over 10 miles on my TJ before.... But I dont have the equipment to do a functional graph of the radiation pattern, and I am certain it extends off to one side quite a lot more than the other of course.


GMRS Talk
If one were able to find a way to roof mount with a ground pane, what are the opinions of something like this - https://www.rightchannelradios.com/products/larsen-low-profile-unity-gain-antenna Might it work better than a cowl mounted option?

Also - considering the mounting locations available to us Jeepers, would one truly benefit from the MXT575? Or, considering these less than optimum mounting location options, would it functionally do no better than the MXT275?

 

[Radio Guy]

Ok so I'm going to open this back up with a couple more questions. Not sure if DaveInDenver from expo is here but a few more details so maybe it will help encourage discussion.


CB Talk
CB radio of choice (not yet ordered) - Uniden CMX760 https://www.rightchannelradios.com/products/uniden-off-road-cmx760

Now, I know there's a lot of talk about cowl mounts and hood lip mounts. But if a guy were to consider a mid load antenna (options below), would it sway a direction to a particular mount type?

https://www.rightchannelradios.com/products/cobra-high-gear-trucker-cb-antenna
https://www.rightchannelradios.com/products/stryker-center-load-antenna-1
https://www.rightchannelradios.com/products/president-texas-cb-antenna

Now to throw another curve ball... I so happen to have TWO 102" whips in the basement. I could get a ball mount and put one on the side of the canopy. I do have a 102 on my TJ, and it works excellent, except for hitting a lot of things. Now the question though, is I am not going to run SSB with the CMX760 - so would a 102 really benefit? I have been able to get over 10 miles on my TJ before.... But I dont have the equipment to do a functional graph of the radiation pattern, and I am certain it extends off to one side quite a lot more than the other of course.


GMRS Talk
If one were able to find a way to roof mount with a ground pane, what are the opinions of something like this - https://www.rightchannelradios.com/products/larsen-low-profile-unity-gain-antenna Might it work better than a cowl mounted option?

Also - considering the mounting locations available to us Jeepers, would one truly benefit from the MXT575? Or, considering these less than optimum mounting location options, would it functionally do no better than the MXT275?

I can tell you there is no magic to CB antennas and the performance is mostly related to their physical length. There are some subtle things that can enhance performance but not much that will make one 4ft antenna greatly outperform another 4ft antenna.

A cowl mount that is not a great idea for a stubby UHF antenna is not a big problem for a CB antenna operating at a much lower frequency. A ball mount and 9ft whip along the outer bed wall either a little behind the cab or behind the rear wheel should work fine. I have a mount on the inside bed wall a few inches below the bed rail and its working very well for CB and HF amateur use. All antennas tune up and work predictably in that location. I would try and keep a ball mount no more that maybe 6 inches below the top bed rail when mounted on the bed side wall.

The hard top roof on my Mojave has ribs on the top making it challenging to mount a sheet metal ground plane on the roof top. On most fiberglass roofs you can simply pop rivet a 12" or larger square or round disc on the roof for a UHF ground plane but you will have to get creative on a Gladiator. Antennas need to be mounted right to the ground plane with no gap if possible, so mounting the antenna on the fiberglass roof with a sheet metal plate on the underside of the roof would not be ideal. There are some no ground plane UHF antennas available that would work fine mounted in the fiberglass roof.

 

[LostWoods]

No concerns for exposure? Thats a lot of power within a couple feet of you...

Are they NGP antennas though? Your pic is similar to one of my mounting option thoughts.

This is totally dependent on your use but if you are just using a 50W dual band you generally aren't going to hit the transmit duty cycle to actually be concerned with the radiation. My brother is an EE who does comms exclusively for a living and screwing around with his test equipment the rf at the driver headrest was more than acceptable (mine mounted driver cowl side). The A-pillar and windscreen seem to knock down a lot of it.

 

[Radio Guy]

This is totally dependent on your use but if you are just using a 50W dual band you generally aren't going to hit the transmit duty cycle to actually be concerned with the radiation. My brother is an EE who does comms exclusively for a living and screwing around with his test equipment the rf at the driver headrest was more than acceptable (mine mounted driver cowl side). The A-pillar and windscreen seem to knock down a lot of it.

I have a cowl/hood hinge mount, a 50w dual band radio and a calibrated Narda RF exposure meter. When I get some time I will make a measurement in the drivers seat at various power levels.

 

[chorky]

I can tell you there is no magic to CB antennas and the performance is mostly related to their physical length. There are some subtle things that can enhance performance but not much that will make one 4ft antenna greatly outperform another 4ft antenna.

A cowl mount that is not a great idea for a stubby UHF antenna is not a big problem for a CB antenna operating at a much lower frequency. A ball mount and 9ft whip along the outer bed wall either a little behind the cab or behind the rear wheel should work fine. I have a mount on the inside bed wall a few inches below the bed rail and its working very well for CB and HF amateur use. All antennas tune up and work predictably in that location. I would try and keep a ball mount no more that maybe 6 inches below the top bed rail when mounted on the bed side wall.

The hard top roof on my Mojave has ribs on the top making it challenging to mount a sheet metal ground plane on the roof top. On most fiberglass roofs you can simply pop rivet a 12" or larger square or round disc on the roof for a UHF ground plane but you will have to get creative on a Gladiator. Antennas need to be mounted right to the ground plane with no gap if possible, so mounting the antenna on the fiberglass roof with a sheet metal plate on the underside of the roof would not be ideal. There are some no ground plane UHF antennas available that would work fine mounted in the fiberglass roof.

Yeah I realize theres not a perfect antenna but I do want to optimize it as much as possible.

Also just to clarify a couple points

• If I used the 102" in my basement, I would put the ball mount on the side of the canopy - not interested in drilling holes in the bed of the truck itself....
  • Most likely though, would be a cowl mounted CB antenna. I do like the 102 on my TJ, but not sure if it is truly beneficial over a mid-load antenna (which is why the question - especially considering the non-SSB radio I am considering)
  • but if a 102 would net a better result overall than a cowl mounted mid-load antenna then that is a route I would consider
• The little puck GMRS antenna, if used, would go on metal (on the canopy not on the fiberglass top). But I am not sure if it really is any 'better' than a standard 1/4 wave antenna
  • that being said, it also probably depends on the radio. If a puck antenna nets better results than a 1/4 wave on cowl, then I see it a possibility
    • this also depends on if there is truly any benefit of the 575 over the 275. if the 275 with a cowl antenna nets the same result as a 575 with the puck antenna then mine as well go with the 275 since its smaller, easier to mount and cheaper

Looking forward to seeing those measurements! Its always been of interest since I use handhelds at work a lot anyway.

 

[Jefe1018]

Throwing out the bracket that works for me, I've been able to talk to another vehicle in my convoy about 4-5 miles back super clear using this and a 4ft FireStik.

https://topsyproducts.com/products/fender-mount-antenna-bracket

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