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

[chorky]

mentioned a 6" whip for GMRS which you could probably run all the time and get plenty of range. You can also swap out the big Stryker for a smaller and lighter CB whip and still be fine for caravanning and off roading. If you like talking across the country on CB then the Stryker will come in handy, but then you would probably be into amplifiers and preamp

Thank you for the response. So I did order a set of these to be used as antenna mounts
https://evomfg.com/products/jeep-jl-gladiator-a-pillar-cowl-light-mounts-pair-black

It for sure puts the antenna closer to the windshield than I really wanted...but they seem much stronger than other options that only bolt into the two cowl bolts. This seems to offer another angle of horizontal stability since it ties into the hinge bolt. But at the cost of putting the antenna closer.....

I do agree that the GMRS should be drivers side and the Stryker to be on the passenger side. My only concern with that is the Stryker whip portion is super flex, and I dont know if it will come into contact with the radio antenna. Hopefully not. I'm also not sure if I want to use both 10" bases which puts the center load at 20" from the mount, or if I want the coil to just be on the mount directly. This will change the SWR of course, and alter how much of the whip needs to be cut I would imagine..... By how much I have no clue. I probably will start with using both 10" base portions since it came put together that way, and see how that works. I also have a heavy duty spring in case its really not looking well...but I would be super worries of that thing swinging back and smashing into the windshield...

I really struggle working under the dash. So I think I am going to use the open gap through the cowl to run the coax, and mount the radios below and behind the drivers seat. I realize that means more cable.... but it's physically easier by a long shot for me to do that, and I am removing the rear seat anyway. They both will also be powered via Aux switch 1, with the cables spliced together and a grounding bolt in the cab on the passenger side that reads 0.01 ohm resistance - so that should work well.

if you see any red flags or further suggestions with this by all means let me know before I get it installed. I really do wish I could find a good solution to mount them on the roof....but being fiberglass, and the sat antenna right in the middle, that really makes for some difficult mounting options, and there's routing the wires as well.

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[Radio Guy]

Thank you for the response. So I did order a set of these to be used as antenna mounts
https://evomfg.com/products/jeep-jl-gladiator-a-pillar-cowl-light-mounts-pair-black

It for sure puts the antenna closer to the windshield than I really wanted...but they seem much stronger than other options that only bolt into the two cowl bolts. This seems to offer another angle of horizontal stability since it ties into the hinge bolt. But at the cost of putting the antenna closer.....

I do agree that the GMRS should be drivers side and the Stryker to be on the passenger side. My only concern with that is the Stryker whip portion is super flex, and I dont know if it will come into contact with the radio antenna. Hopefully not. I'm also not sure if I want to use both 10" bases which puts the center load at 20" from the mount, or if I want the coil to just be on the mount directly. This will change the SWR of course, and alter how much of the whip needs to be cut I would imagine..... By how much I have no clue. I probably will start with using both 10" base portions since it came put together that way, and see how that works. I also have a heavy duty spring in case its really not looking well...but I would be super worries of that thing swinging back and smashing into the windshield...

I really struggle working under the dash. So I think I am going to use the open gap through the cowl to run the coax, and mount the radios below and behind the drivers seat. I realize that means more cable.... but it's physically easier by a long shot for me to do that, and I am removing the rear seat anyway. They both will also be powered via Aux switch 1, with the cables spliced together and a grounding bolt in the cab on the passenger side that reads 0.01 ohm resistance - so that should work well.

if you see any red flags or further suggestions with this by all means let me know before I get it installed. I really do wish I could find a good solution to mount them on the roof....but being fiberglass, and the sat antenna right in the middle, that really makes for some difficult mounting options, and there's routing the wires as well.

Those mounts will work for the CB antenna, not my favorite due to putting the antenna feed point too high above the ground plane which will reduce efficiency and may cause tuning problems. Those mounts will not work with most NMO mounts. Those need a 3/4" dia hole in thinner material, otherwise the inside of the mount gets recessed too far and the antenna center pin may not reach the mount. The mounts also seem very expensive.

For the CB antenna I was thinking of the mounts that bolt to the flat area under the hood when the hood is open and they protrude out the side of the hood opening. Those put the antenna base right near the ground plane and are much less $$. I would not recommend that particular mount for GMRS if you were going to use a 6" whip or pud type. The top of the hood and right on the sheet metal is best and raising the base of a GMRS antenna a few inches above the sheet metal with the mounts you chose will have measurable loss in performance.

 

[chorky]

Those mounts will work for the CB antenna, not my favorite due to putting the antenna feed point too high above the ground plane which will reduce efficiency and may cause tuning problems. Those mounts will not work with most NMO mounts. Those need a 3/4" dia hole in thinner material, otherwise the inside of the mount gets recessed too far and the antenna center pin may not reach the mount. The mounts also seem very expensive.

For the CB antenna I was thinking of the mounts that bolt to the flat area under the hood when the hood is open and they protrude out the side of the hood opening. Those put the antenna base right near the ground plane and are much less $$. I would not recommend that particular mount for GMRS if you were going to use a 6" whip or pud type. The top of the hood and right on the sheet metal is best and raising the base of a GMRS antenna a few inches above the sheet metal with the mounts you chose will have measurable loss in performance.

ok....well....

I was figuring on drilling the hole wider but didnt think the thickness or offset above the sheet metal would be such a big deal.

So you are suggesting a mount such as this? https://www.quadratec.com/products/96080_0056_07.htm

One bolt leaves me a little concerned for the strength aspect.


Ok what about this option.
Drilling - yes drilling, a hole on either side to accommodate cb/gmrs in the white circled location? That piece I'm sure can be purchased later from Jeep if necessary as a replacement. But not sure if that sheet metal (I think it's steel????) is strong enough? I certainly don't want an antenna to rip through.

I also can't quite tell what is under that portion if it would be a nice flat place for a mount, or how that piece of cowl is removed - if anyone knows please chime in.


I could possibly revisit the idea of mounting on the roof - but really not sure how to solve the ground plane situation with the fiberglass. Strangely though the Stryker antenna website says that for bad ground planes, to just run a ground wire from the mount to a chassis ground but they dont specify it as a no ground plane antenna - but it is somewhat designed for truckers. So maybe that would work for the CB at least? It would put the whole thing quite high in the air but I'm not as worried about that much as branches coming in from the side. I could then use something like this (https://www.amazon.com/Renogy-RNG-M...olar%20roof%20wire%20moun,aps,159&sr=8-5&th=1) to drill through the fiberglass roof and route wires down into the cab (I do not plan on ever taking the top off). The antennas could be mounted on simple cross bars, maybe one forward of the factory sat antenna, and one behind? that would give decent antenna separation, and possibly reduce interference with the sat antenna? Just not sure about that darn ground pane situation. What's your thoughts on this idea?

 

[Radio Guy]

ok....well....

I was figuring on drilling the hole wider but didnt think the thickness or offset above the sheet metal would be such a big deal.

So you are suggesting a mount such as this? https://www.quadratec.com/products/96080_0056_07.htm

One bolt leaves me a little concerned for the strength aspect.


Ok what about this option.
Drilling - yes drilling, a hole on either side to accommodate cb/gmrs in the white circled location? That piece I'm sure can be purchased later from Jeep if necessary as a replacement. But not sure if that sheet metal (I think it's steel????) is strong enough? I certainly don't want an antenna to rip through.

I also can't quite tell what is under that portion if it would be a nice flat place for a mount, or how that piece of cowl is removed - if anyone knows please chime in.


I could possibly revisit the idea of mounting on the roof - but really not sure how to solve the ground plane situation with the fiberglass. Strangely though the Stryker antenna website says that for bad ground planes, to just run a ground wire from the mount to a chassis ground but they dont specify it as a no ground plane antenna - but it is somewhat designed for truckers. So maybe that would work for the CB at least? It would put the whole thing quite high in the air but I'm not as worried about that much as branches coming in from the side. I could then use something like this (https://www.amazon.com/Renogy-RNG-MTS-CE-Housing-Caravans-Marine/dp/B01N04XAHC/ref=sr_1_5?crid=22M9LV83S2SPJ&keywords=solar+roof+wire+mount&qid=1674930881&sprefix=solar%20roof%20wire%20moun,aps,159&sr=8-5&th=1) to drill through the fiberglass roof and route wires down into the cab (I do not plan on ever taking the top off). The antennas could be mounted on simple cross bars, maybe one forward of the factory sat antenna, and one behind? that would give decent antenna separation, and possibly reduce interference with the sat antenna? Just not sure about that darn ground pane situation. What's your thoughts on this idea?

I've seen mounts similar to the Quadratech but with at least two mounting bolts and I would put it a little further towards the rear of the hood. The ground plane should be sufficient for a CB antenna and it should tune up ok there. I'm not a fan of that location for a UHF antenna but it will work. For other mounting locations or mounts you don't want to create a situation where you have to start adding wires to your CB mount to improve the ground plane. That's a road to avoid.

The cowl piece on my trunk that is at the rear sides of the hood that curves down from the cowl is all plastic. For my hood mounted antennas I took those plastic pieces off and covered the underside with conductive aluminum tape which grounds to the bolt mounts to improve my ground plane, but I'm a bit more fanatical than most.

 

[chorky]

I've seen mounts similar to the Quadratech but with at least two mounting bolts and I would put it a little further towards the rear of the hood. The ground plane should be sufficient for a CB antenna and it should tune up ok there. I'm not a fan of that location for a UHF antenna but it will work. For other mounting locations or mounts you don't want to create a situation where you have to start adding wires to your CB mount to improve the ground plane. That's a road to avoid.

The cowl piece on my trunk that is at the rear sides of the hood that curves down from the cowl is all plastic. For my hood mounted antennas I took those plastic pieces off and covered the underside with conductive aluminum tape which grounds to the bolt mounts to improve my ground plane, but I'm a bit more fanatical than most.

Ok I will keep looking - haven't seen one that has two bolts yet. What type of situations would require a wire for a ground plane? I'm really not familiar with that need or when to know when it is needed in order to try and avoid that type of mounting.

Yeah I had a feeling the curved parts were plastic. I can't use the typical cowl light mounts that have 4 points of contact due to other items in the works that it would interfere with.

So that is interesting that aluminum tape is enough to be a sufficient ground plane! I thought it would have had to be a larger thicker bit of aluminum..... I happen to have some for ductwork I was doing on the house recently. Thats a great idea! But to understand it correctly, does the aluminum tape NEED to physically touch metal in order to actually ground? I thought the term 'ground plane' really only reflected on the need for an antenna signal to bounce off a piece of metal. Maybe I understood this wrong?

That brings me to question again the roof mount idea. What if I did that, and used the pass-through that I posted the link of, and then used aluminum tape on the inside of the roof and covered it up with a liner - but left open a decent portion in the center for the satellite antenna. I believe the satellite antenna is the only thing that needs to transmit signal up there. This still, however, means that antennas would be raised above the ground plane though - something you said earlier was not a great idea.

Or would the cowl just still be a better place?

 

[Radio Guy]

Ok I will keep looking - haven't seen one that has two bolts yet. What type of situations would require a wire for a ground plane? I'm really not familiar with that need or when to know when it is needed in order to try and avoid that type of mounting.

Yeah I had a feeling the curved parts were plastic. I can't use the typical cowl light mounts that have 4 points of contact due to other items in the works that it would interfere with.

So that is interesting that aluminum tape is enough to be a sufficient ground plane! I thought it would have had to be a larger thicker bit of aluminum..... I happen to have some for ductwork I was doing on the house recently. Thats a great idea! But to understand it correctly, does the aluminum tape NEED to physically touch metal in order to actually ground? I thought the term 'ground plane' really only reflected on the need for an antenna signal to bounce off a piece of metal. Maybe I understood this wrong?

That brings me to question again the roof mount idea. What if I did that, and used the pass-through that I posted the link of, and then used aluminum tape on the inside of the roof and covered it up with a liner - but left open a decent portion in the center for the satellite antenna. I believe the satellite antenna is the only thing that needs to transmit signal up there. This still, however, means that antennas would be raised above the ground plane though - something you said earlier was not a great idea.

Or would the cowl just still be a better place?

Some people have put CB antennas on raised mounts above tire carriers with no sheet metal in sight (which don't work) and something like that would benefit from some clever ground wires. Since RF ground currents flow from the antenna feedpoint you want a ground plane to be electrically connected to the base of the antenna. An ultimate connection back to the battery has nothing to do with antenna ground plane, its all about metal right under and attached to the antenna.

If you go roof mount with the GMRS antenna the ground plane requirements are not bad at about 1ft in diameter. You could make an X on the underside of the fiberglass roof with two 1ft long strips of wide aluminum tape. More is better like a star shape or a continuous sheet. You would also have to use a thick mount NMO connector that uses about a 5/8" dia hole and has a connector at the end. For CB you would have to cover a major area with conductive tape plus strengthen the roof for that large antenna. Unless you know you are in a fringe area of a repeater or someone you talk with and need the extra height and performance of a roof mounted antenna I would just go with the cowl or hood type mount.

 

[chorky]

Some people have put CB antennas on raised mounts above tire carriers with no sheet metal in sight (which don't work) and something like that would benefit from some clever ground wires. Since RF ground currents flow from the antenna feedpoint you want a ground plane to be electrically connected to the base of the antenna. An ultimate connection back to the battery has nothing to do with antenna ground plane, its all about metal right under and attached to the antenna.

If you go roof mount with the GMRS antenna the ground plane requirements are not bad at about 1ft in diameter. You could make an X on the underside of the fiberglass roof with two 1ft long strips of wide aluminum tape. More is better like a star shape or a continuous sheet. You would also have to use a thick mount NMO connector that uses about a 5/8" dia hole and has a connector at the end. For CB you would have to cover a major area with conductive tape plus strengthen the roof for that large antenna. Unless you know you are in a fringe area of a repeater or someone you talk with and need the extra height and performance of a roof mounted antenna I would just go with the cowl or hood type mount.

Well I was thinking mounting on a roof cross bar not the roof itself.... but that would also raise the antenna base connection probably, oh idk, 4" above any connective tape - maybe even a little more depending on how thick the fiberglass roof is.

But interesting about the ground plane, I understood it differently, so glad I asked. So, just to check my understanding, if the antennas were on a rack on the roof, and if there was tape underside of the roof, then there would need to be a wire connecting from the tape itself to the base of the antenna mount on the roof?

I only considered that as an option because the terrain here (western Montana) is very very hilly and even our government (VHF I believe) radios have a difficult time reaching over just one drainage over, which could be less than a mile.

So if the CB on the roof requires a huge ground plane, then why would a CB on the cowl not have the same requirement? Or does the fact that the steel hood being right there make the difference?

 

[chorky]

Some people have put CB antennas on raised mounts above tire carriers with no sheet metal in sight (which don't work) and something like that would benefit from some clever ground wires. Since RF ground currents flow from the antenna feedpoint you want a ground plane to be electrically connected to the base of the antenna. An ultimate connection back to the battery has nothing to do with antenna ground plane, its all about metal right under and attached to the antenna.

If you go roof mount with the GMRS antenna the ground plane requirements are not bad at about 1ft in diameter. You could make an X on the underside of the fiberglass roof with two 1ft long strips of wide aluminum tape. More is better like a star shape or a continuous sheet. You would also have to use a thick mount NMO connector that uses about a 5/8" dia hole and has a connector at the end. For CB you would have to cover a major area with conductive tape plus strengthen the roof for that large antenna. Unless you know you are in a fringe area of a repeater or someone you talk with and need the extra height and performance of a roof mounted antenna I would just go with the cowl or hood type mount.

Another thought - if I were to get a standard roof rack, and sheet it with thin gauge aluminum for ground plane, and attach both antennas to that - would that work well?

This of course would depend entirely on the ability to find a satellite antenna that will function with Sirius and the factory Jeep GPS and guardian that I can move and mount outside on top of said rack so it will work as well.....

 

[Radio Guy]

Well I was thinking mounting on a roof cross bar not the roof itself.... but that would also raise the antenna base connection probably, oh idk, 4" above any connective tape - maybe even a little more depending on how thick the fiberglass roof is.

But interesting about the ground plane, I understood it differently, so glad I asked. So, just to check my understanding, if the antennas were on a rack on the roof, and if there was tape underside of the roof, then there would need to be a wire connecting from the tape itself to the base of the antenna mount on the roof?

I only considered that as an option because the terrain here (western Montana) is very very hilly and even our government (VHF I believe) radios have a difficult time reaching over just one drainage over, which could be less than a mile.

So if the CB on the roof requires a huge ground plane, then why would a CB on the cowl not have the same requirement? Or does the fact that the steel hood being right there make the difference?

If you put an NMO mount in the fiberglass roof and make an aluminum tape ground plane on the underside, the NMO mount will bite into the tape on the underside and make good contact to the ground side of the mount. The hood is a lot of sheet metal and makes an adequate ground plane for CB if its mounted in the center. Off to the side is a compromise in performance and directionality but its still enough sheet metal for the antenna to match up ok.

 

[Radio Guy]

Another thought - if I were to get a standard roof rack, and sheet it with thin gauge aluminum for ground plane, and attach both antennas to that - would that work well?

This of course would depend entirely on the ability to find a satellite antenna that will function with Sirius and the factory Jeep GPS and guardian that I can move and mount outside on top of said rack so it will work as well.....

Its not out of the question to make a sheet metal ground plane for a UHF antenna sitting on a rack but not really for CB. When our local fire dept went to UHF in the 1970s they had the antennas mounted to a 12" dia round disc for a ground plane, elevated above the open cabs (this is sunny So Cal).

 

[chorky]

Its not out of the question to make a sheet metal ground plane for a UHF antenna sitting on a rack but not really for CB. When our local fire dept went to UHF in the 1970s they had the antennas mounted to a 12" dia round disc for a ground plane, elevated above the open cabs (this is sunny So Cal).

Well back to the drawing board it seems. Ok so a few more questions if you don't mind entertaining and sharing knowledge....

With those other hinge mounts I posted earlier - would there be a way to make those work sufficiently? Or do they just cause far too many problems? I could use them for another purpose but since they're on the way.....

So another thought - since I plan on a RTT, what about a mount (for the CB??) at the front of this so that one doesn't have to worry about a moving cable when opening and repeatedly closing the top

This would provide the back half with a ground plane since it is all aluminum. Not sure how that would suffice? My canopy is also stainless steel so there is a lot of metal going on back there. Although it still requires cable management to get it to the cab.

But, if that would be sufficient (only mentioning because I dont remember if I made mention of it before) then I could probably still get the GMRS antenna in the back half of the fiberglass roof - maybe.

However, I dont know if that puts the antennas too close to each other.


Not opposed totally to that hood lip mount but I can't seem to find that one that uses two bolts instead of just one. The Stryker seems too heavy to realistically use just one bolt imo.

 

[Radio Guy]

I would try the Evo mount on the passenger side with a 3/8-24 mount and the Stryker antenna. Its not optimum but it will be easy and you will get a signal down the road. Since an NMO will not work with that mount there is still a trunk lip NMO mount for the GMRS antenna on the drivers side hood near a hinge or a dual bolt mount that sticks out the side of the hood opening on the drivers side.

You have to ask do I want maximum performance and distance on both radios or is good enough good enough? I think the hood is plenty good enough. If not I would want to look over the sheet metal on the roof tent thing and see how to incorporate that into the antenna system. It will be more work and the antennas may be subject to hitting stuff up there where the hood is lower and safer.

 

[Glad Jeeper]

This works really well, despite what the comments say. I was politely informed this "would not work". Well it works and better than thought. While on trail I can receive and transmit up to 5 miles.

 

[chorky]

I would try the Evo mount on the passenger side with a 3/8-24 mount and the Stryker antenna. Its not optimum but it will be easy and you will get a signal down the road. Since an NMO will not work with that mount there is still a trunk lip NMO mount for the GMRS antenna on the drivers side hood near a hinge or a dual bolt mount that sticks out the side of the hood opening on the drivers side.

You have to ask do I want maximum performance and distance on both radios or is good enough good enough? I think the hood is plenty good enough. If not I would want to look over the sheet metal on the roof tent thing and see how to incorporate that into the antenna system. It will be more work and the antennas may be subject to hitting stuff up there where the hood is lower and safer.

couldnt i just drill out the hole some and use a step bit also to make it a little “thinner” where the nmo mount would go?

assuming swr readings are within a decent spec, what kind of range might you think I could expect for the cb and gmrs (if i can make it work) on those mount? Just for in testing to see if it is in fact working ok.

 

[Radio Guy]

couldnt i just drill out the hole some and use a step bit also to make it a little “thinner” where the nmo mount would go?

assuming swr readings are within a decent spec, what kind of range might you think I could expect for the cb and gmrs (if i can make it work) on those mount? Just for in testing to see if it is in fact working ok.

The steps in a step bit are really shallow, you might need to go about 3/8" wider than the hole to make a rectangular recessed spot for the back side of the NMO mount to fit in. I did that once using a hand held grinder in similar thickness metal to the Evo mount and it was a big PIA. If you had a typical roof mount NMO mount you could use that as a guide on how much metal to remove to bring the top contact point up to needed height.

You could also use a "thick mount" NMO like this but you have to solder in your own coax and weather proof it. You also have to make sure the material is not too thin where you have to use spacers to leave the correct height on the center contact to the antenna.
https://www.ebay.com/itm/223457312586?hash=item340717ff4a:g:X7gAAOSwXL1clOzM&amdata=enc:AQAHAAAA4NhRdM4pMtgaYxXTYtiB4GhcUerZ50fjGli3JkmqhY7+inhdwZYKPYPwL35Nm//ioDw3uTEy2wAzm+4TbIpyf6JcOhrA4g2PIYg0VzPckRh2Ot1l+a3xEUW8GWyc2jziUq5BcNooPcnvrXeOvYnlyJKgZm/zE/CLfVSmYIGlEIOj5SKviRGNSlQGc+0BiG3rU300oW2aHKS1akxEMs/AbnnMNQCHLYduNdo6HQwY2CJv4CA7RzUG0/jEWpwcD5zIR1KPsAkagrlCdKBDNFfcorUX2r6O2qQ+rkji4NDJLVa7|tkp:Bk9SR_yo0fy_YQ

On the post above with the short antenna on the blue truck with 5mi range, I get well in excess of 20mi range down the open highway to most anyone and have done further depending on how good the antenna is at the other end. I easily do 75mi or more to GMRS and UHF amateur repeaters around here with my trunk lip mount on the hood.

For chorky you should get 20mi range down the highway on GMRS with a hood mounted antenna that is right on the hood not elevated and CB depends entirely on if the skip is in and how noisy the band is. If its a real quite day with no skip I would expect at least 5 to 10mi to other vehicles with good antennas and 10-20mi to base stations. On a real noisy day range can be just a mile or so and people on the other side of the country will be much stronger than the guy a mile up the road from you.

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