CB install in Expedition

[niemern]

I don't do e-mail. Feel free to share your questions here so others can benefit from the information.

New to this forum and really need your help, and completely value your opinion after reading hundreds of your posts... I am guessing you are a former "Coastie" radio man from your icon.
I have an aluminum body SUV (2018 Ford Expedition) and would like to install a CB radio. From you many posts, I understand that your recommendation is to use a center roof mounted NMO antenna like the Larsen NMO-27 or Laird equivalent.
My Ford dealer warns me that the ferrous metal of the NMO mount, or any ferrous metal mounting, will create corrosion with the aluminum body. Dissimilar metals create a galvanic couple and over time create corrosion. Besides, my wife would have a fit if I drilled a 3/4" hole in the roof of our SUV.
I am aware that there are alternatives, such as front hood/fender mounts, or the factory roof rack rails that are actually ferrous metal on my vehicle but not grounded to the chassis. When I put one lead of an ohm meter on the roof rail and the other to chassis ground, it shows open circuit or infinity. I could fashion a bracket on the roof rail with a steel plate and place a magnetic base for the Larsen antenna. I would just have to screw it on and remove it every time I went in or out of the garage. Not a convenient thing, but I would do it if this is the only viable option. Your prior posts however indicate this roof rail set up with the antenna few inches off the roof would not provide a good ground plane.
Regarding the fender/ hood options, I am told that for coil loaded antennas, either base or center loaded, the entire coil must be located above the roofline of the vehicle for good SWR and signal pattern. Hustler makes a center loaded, 3-foot antenna that would get the bottom of the coil just above the roof line.
All this aside, I do not understand RF ground plane theory, and am concerned after reading your posts that that the front mounted fender or hood lip mounts will not be ideal or provide reception beyond 1-2 miles max.
Any suggestions would be welcomed. Thanks very much in advance and thank you for your service.

 

[mmckenna]

New to this forum and really need your help, and completely value your opinion after reading hundreds of your posts... I am guessing you are a former "Coastie" radio man from your icon.
I have an aluminum body SUV (2018 Ford Expedition) and would like to install a CB radio. From you many posts, I understand that your recommendation is to use a center roof mounted NMO antenna like the Larsen NMO-27 or Laird equivalent.
My Ford dealer warns me that the ferrous metal of the NMO mount, or any ferrous metal mounting, will create corrosion with the aluminum body. Dissimilar metals create a galvanic couple and over time create corrosion.

That corrosion would require moisture. The NMO mounts are sealed so water isn't an issue. Plus, the mounts are not steel, they are usually brass or stainless.

Ambulance/fire truck bodies have been aluminum for decades. Installing an NMO mount on aluminum is not an issue.

Besides, my wife would have a fit if I drilled a 3/4" hole in the roof of our SUV.

My wife is 5'1". She'd never know. But seriously, don't piss her off.
Fortunately mine understands and has a ham ticket, so she had no problem with me installing an antenna on top of her Chevy Colorado when it was about 2 days old.

I am aware that there are alternatives, such as front hood/fender mounts, or the factory roof rack rails that are actually ferrous metal on my vehicle but not grounded to the chassis. When I put one lead of an ohm meter on the roof rail and the other to chassis ground, it shows open circuit or infinity. I could fashion a bracket on the roof rail with a steel plate and place a magnetic base for the Larsen antenna. I would just have to screw it on and remove it every time I went in or out of the garage. Not a convenient thing, but I would do it if this is the only viable option. Your prior posts however indicate this roof rail set up with the antenna few inches off the roof would not provide a good ground plane.

Right, you want the antenna down on the ground plane, not hovering above it.

Regarding the fender/ hood options, I am told that for coil loaded antennas, either base or center loaded, the entire coil must be located above the roofline of the vehicle for good SWR and signal pattern. Hustler makes a center loaded, 3-foot antenna that would get the bottom of the coil just above the roof line.

The base coil does not radiate much energy, the whip does that.

All this aside, I do not understand RF ground plane theory, and am concerned after reading your posts that that the front mounted fender or hood lip mounts will not be ideal or provide reception beyond 1-2 miles max.

No, it's not ideal, but it'll work as long as your expectations are set correctly. If you want maximum range from your radio, you really want to pay attention to the antenna installation. It's the radios interface to the outside world, and you want it to work well.

Since it sounds like you don't want to do the mount on the roof, then you have to accept the drawbacks.

But 1-2 miles probably won't be a big deal. If that's the mount that works for your application and wife, then that's what you've got to do.

I'd still go with the Larsen NMO-27 on that mount. Good antenna that will outlast your vehicle, and probably you'll pass the antenna down to your grandkids.

Any suggestions would be welcomed. Thanks very much in advance and thank you for your service.

Happy to help.

 

[Hans13]

I gain knowledge from just about every one of your posts, mmckenna. Thanks.

 

[mmckenna]

I gain knowledge from just about every one of your posts, mmckenna. Thanks.

Thanks. I'm still learning myself, so take what I saw with a bit of salt.

 

[AK9R]

All the NMO mounts I've seen are either made of brass or stainless steel. Granted, some installations may require a bracket to attach the NMO mount to the body and that bracket may be plain steel.

That said, Ford has published a Special Vehicle Engineering bulletin, attached, that discusses how to attach accessories to aluminum body panels. The bulletin gives some recommendations for ways to protect against galvanic corrosion.

 

[RFI-EMI-GUY]

If the roof is actually aluminum (I had to run out to my new-to-me 2013 Expedition 3rd Gen, to confirm it is steel) and you are probably correct, there are potential (ha ha!) galvanic issues with stainless steel, brass and other materials. Zinc plated brass might be OK as zinc is sacrificial. I would not rule out an NMO mount on the roof, as performance wise it is best alternative. I would however shop around for an NMO mount designed specifically for aluminum roof. I would also be very careful to ground the radio properly and securely. This is definitely a case where a cigar lighter powered radio would be a problem. For there to be corrosion the metals must be significantly different galvanically and there needs to be moisture as Mmckenna points out. If you can minimize the galvanic potential and eliminate the moisture you should be fine.

 

[RFI-EMI-GUY]

You might give Breedlove a call and explain the problem. It looks like they may be working on it, though they could describe their products a bit better.

NMO Antenna Roof Mount #504

3 inches in diameter and 3/8 inch thickaluminum top plate with a solid brass NMOneoprene rubber gasket2 inch round nut with ground screwstainless steel screws for ring terminal connectionrequires only 1 inch clearance on the inside to installNeeds only one 5/8 inch hole to install on sheet metal

breedlovemounts.com

NMO-4 NMO MOUNT | eBay

Solid NMO mount to SO 239.

www.ebay.com

 

[mmckenna]

For the galvanic corrosion to happen, you have to have an electrolyte. A properly installed NMO mount will stay dry.

I live a few miles in from the Pacific ocean, and I work much closer. Salt air, fog, etc. Multiple Ford trucks with aluminum bodies, plus our Ford police utilities. All have multiple NMO mounts. My work truck has 3 NMO mounts and they've been on there for 8 years. Not to mention all the fire vehicles and ambulances with aluminum bodies. Never seen an issue with corrosion on a properly installed mount.

None of the big LMR antenna manufacturers are having an issue with any of this. The only place I can find people talking about this are the CB'ers and ham radio operators looking for excuses about why they won't do a proper antenna installation.

 

[slowmover]

https://www.k0bg.com/images/antenna/Q-222R1.pdf

 

[RFI-EMI-GUY]

https://www.k0bg.com/images/antenna/Q-222R1.pdf

The stuff in red is interesting. NO RTV sealer. That is important to consider. Wish they recommended an alternative.

 

[AK9R]

https://www.k0bg.com/images/antenna/Q-222R1.pdf

That's the same document I posted in message #5.

If the roof is actually aluminum (I had to run out to my new-to-me 2013 Expedition 3rd Gen, to confirm it is steel)

Expeditions have had aluminum bodies since the 4th gen came out in the 2018 model year.

 

[W2JGA]

On another note, what will the XYL think of when she starts hearing the conversations on the chicken band? All this work just to have to turn the radio off?

 

[WSHH591]

New issue for the forum to please consider and respond to regarding this install... within three inches of the dome light area where I plan to drill the hole for NMO mount is a Ford factory 902 MHz transceiver for the keyless entry system mounted up in the headliner. See photo I found on the internet. Ford tech support cannot provide any details as to power level of this device, but I am guessing its well below 100 milliwatts. The question is, if I attach either a CB radio antenna to this NMO mount at this location and transmit in the 27 MHz band at 4 watts, or a GMRS UHF (462 - 467 MHz), 50-watt radio, will it damage the factory keyless entry transceiver?
Also in the headliner are cell phone antenna and amplifier and various other electronic control modules for back up cameras, lane keeping system and various associated wire harnesses (see attached Ford parts manual image). I am only concerned about an RF signal from a two-way radio damaging one of these devices.

I contacted Ford Tech Support, and they are of no technical help. They tell me to contact the radio manufacturers. I contacted Midland and Cobra, and they have no real advice other than try another location other than the center of the roof, where this keyless entry transceiver is located. I downloaded the Ford factory Upfitters Guide for the police/fire version of this vehicle and the only mention of antenna location is to NOT install a driver's side front fender mount, so as not to interfere with the anti-lock braking control module.

Because of the many roof support braces and other interfering devices there are no other locations to drill a hole in this vehicle's roof without causing a problem or drilling into something (No way I am taking headliner down). That would mean using a front fender mount or luggage rack mount, both of which are not as optimum, as I have learned through hundreds of discussions on this forum. I have purchased a Larsen NMO mount with attached LR240 coax to achieve the best RF shielding I can. Before I drill the hole, I would appreciate your thoughts.

Sorry to say that the car companies are making it more and more difficult to permanently install 2-way radios in newer vehicles because of the sophisticated electronics. A local radio installer told me that VW actually has a statement in their warranties that voids the car's warranty if a two-way radio is installed. Many thanks...

 

[mmckenna]

New issue for the forum to please consider and respond to regarding this install... within three inches of the dome light area where I plan to drill the hole for NMO mount is a Ford factory 902 MHz transceiver for the keyless entry system mounted up in the headliner. See photo I found on the internet. Ford tech support cannot provide any details as to power level of this device, but I am guessing its well below 100 milliwatts. The question is, if I attach either a CB radio antenna to this NMO mount at this location and transmit in the 27 MHz band at 4 watts, or a GMRS UHF (462 - 467 MHz), 50-watt radio, will it damage the factory keyless entry transceiver?

Not an issue.
The radio for the locks is inside the vehicle and the CB/GMRS antenna will be outside. The 900MHz radio should have filtering that attenuates signals outside the 900MHz band. The CB/GMRS radio should have filtering that attenuates signals outside the CB or GMRS bands.
Lots of these vehicles used in public safety use running 100 watts on low band, 100 watts on VHF and UHF, and 35 watts on 7/800MHz, and no issues.
Your CB and/or GMRS, ham, etc. won't be an issue.

Also in the headliner are cell phone antenna and amplifier and various other electronic control modules for back up cameras, lane keeping system and various associated wire harnesses (see attached Ford parts manual image). I am only concerned about an RF signal from a two-way radio damaging one of these devices.

Good concerns to have, but Ford thinks of this ahead of time. Lots of these vehicles running more radios/more power than you ever will and not an issue. Ford actually tests for this sort of stuff.

I contacted Ford Tech Support, and they are of no technical help. They tell me to contact the radio manufacturers. I contacted Midland and Cobra, and they have no real advice other than try another location other than the center of the roof, where this keyless entry transceiver is located. I downloaded the Ford factory Upfitters Guide for the police/fire version of this vehicle and the only mention of antenna location is to NOT install a driver's side front fender mount, so as not to interfere with the anti-lock braking control module.

There's your answer. And that Drivers Side Front Fender area is where a lot of hobbyists who are not willing to drill the hole mount their antennas, yet they survive.

You'll be fine with your installation. You are putting some good thought into this, but taking it a bit farther than you need to.

Because of the many roof support braces and other interfering devices there are no other locations to drill a hole in this vehicle's roof without causing a problem or drilling into something (No way I am taking headliner down). That would mean using a front fender mount or luggage rack mount, both of which are not as optimum, as I have learned through hundreds of discussions on this forum. I have purchased a Larsen NMO mount with attached LR240 coax to achieve the best RF shielding I can. Before I drill the hole, I would appreciate your thoughts.

Visualize around the dome light. Other option is to pull down one side of the headliner enough to visualize what is up there. Or, get a flexible camera/borescope and use that.
Or, find a local public safety agency that is running these vehicles and see where they mounted theres.
Usually center line of the roof isn't an issue, but you'd need to look at your specific vehicle.

Sorry to say that the car companies are making it more and more difficult to permanently install 2-way radios in newer vehicles because of the sophisticated electronics. A local radio installer told me that VW actually has a statement in their warranties that voids the car's warranty if a two-way radio is installed. Many thanks...

Some manufactures are, but keep in mind these Ford, Chevy and Dodge trucks are used heavily in the public safety/public service fields and there are probably tens of thousands of these vehicles out there on the road with radios installed in them without problems.
I just did a 2025 Ford F250 and it was as easy as any of the other vehicles I've done in the last 30 years.
It really depends on the vehicle you choose. Not all are well suited to radio installations.

 

[MUTNAV]

Not an issue.
The radio for the locks is inside the vehicle and the CB/GMRS antenna will be outside. The 900MHz radio should have filtering that attenuates signals outside the 900MHz band. The CB/GMRS radio should have filtering that attenuates signals outside the CB or GMRS bands.
Lots of these vehicles used in public safety use running 100 watts on low band, 100 watts on VHF and UHF, and 35 watts on 7/800MHz, and no issues.
Your CB and/or GMRS, ham, etc. won't be an issue.



Good concerns to have, but Ford thinks of this ahead of time. Lots of these vehicles running more radios/more power than you ever will and not an issue. Ford actually tests for this sort of stuff.



There's your answer. And that Drivers Side Front Fender area is where a lot of hobbyists who are not willing to drill the hole mount their antennas, yet they survive.

You'll be fine with your installation. You are putting some good thought into this, but taking it a bit farther than you need to.



Visualize around the dome light. Other option is to pull down one side of the headliner enough to visualize what is up there. Or, get a flexible camera/borescope and use that.
Or, find a local public safety agency that is running these vehicles and see where they mounted theres.
Usually center line of the roof isn't an issue, but you'd need to look at your specific vehicle.



Some manufactures are, but keep in mind these Ford, Chevy and Dodge trucks are used heavily in the public safety/public service fields and there are probably tens of thousands of these vehicles out there on the road with radios installed in them without problems.
I just did a 2025 Ford F250 and it was as easy as any of the other vehicles I've done in the last 30 years.
It really depends on the vehicle you choose. Not all are well suited to radio installations.

What sort of vehicles would be not well suited for a radio install... Thinking of a new vehicle and it seems like something to consider.

Thanks
Joel

 

[mmckenna]

What sort of vehicles would be not well suited for a radio install... Thinking of a new vehicle and it seems like something to consider.

Thanks
Joel

To me, the challenge is the placement of a control head, unless the application calls for a HHCH. Finding suitable/safe location for the RF deck, and of course, a proper ground plane for the antenna to sit on.

The other variable is the tolerance of the user to where/how things get installed. Some are "absolutely NO holes" and that's a challenge to accommodate. Some are OK with radios intruding on passenger space.

Then you have to look at air bag deployment zones, etc.

Truth is, nothing is impossible, just depends on how much you want to take on. We just got two new Ford Escapes for the deputy chief and someone else, those would work well with a hand held control head, but I'd hate to have to install a full size control head in one of those.

Anything with a sun roof is out in my book. I want a good ground plane for a permanent mount antenna. I've done installs on SUV's and trucks with a sun roof before, but I wouldn't buy one myself.

Subcompact sedans would be a personal nightmare in my book. Looking at my brother in laws Subaru makes me cringe. I know people have installed in those, but I'm glad I never had to do one. My sister has a Tesla 3 that I wouldn't want to try to put a radio in.

But, generally, with some carful planning, anything is possible if you take your time and have some fabrication skills.

 

[nokones]

If you run the radio positive lead to the battery and not to the cigarette/accessory outlet and connect the radio ground lead to a factory chassis grounding point, and the antenna mount has continuity to chassis/body ground when the coax cable is not connected to the radio, you should be good to go. But, do check your VSWR and trim/tune your antenna accordingly.

 

[MUTNAV]

To me, the challenge is the placement of a control head, unless the application calls for a HHCH. Finding suitable/safe location for the RF deck, and of course, a proper ground plane for the antenna to sit on.

The other variable is the tolerance of the user to where/how things get installed. Some are "absolutely NO holes" and that's a challenge to accommodate. Some are OK with radios intruding on passenger space.

Then you have to look at air bag deployment zones, etc.

Truth is, nothing is impossible, just depends on how much you want to take on. We just got two new Ford Escapes for the deputy chief and someone else, those would work well with a hand held control head, but I'd hate to have to install a full size control head in one of those.

Anything with a sun roof is out in my book. I want a good ground plane for a permanent mount antenna. I've done installs on SUV's and trucks with a sun roof before, but I wouldn't buy one myself.

Subcompact sedans would be a personal nightmare in my book. Looking at my brother in laws Subaru makes me cringe. I know people have installed in those, but I'm glad I never had to do one. My sister has a Tesla 3 that I wouldn't want to try to put a radio in.

But, generally, with some carful planning, anything is possible if you take your time and have some fabrication skills.

Thanks...
That's pretty much what I was looking for... Subcompacts aren't a good fit. I don't know how well a roof mount would work on it anyway, with the Chevy Spark, the roof gets dented by acorns in the fall (big dents), and I don't think my ( Spousal unit... 1..., Ea.... ) would approve.

So I would be looking at a trunk lip mount, and a tiny head on the dash top at the most.

Thanks again
Joel

 

[WSHH591]

I appreciate the input. I am going to move forward with installing the NMO roof mount. Based on the input from mmckenna, I think all will be well.
Okay, with the NMO mounted, next subject... I made these two CB antennas from the following parts - EMWAVE X-nut base for NMO mounting, aluminum tripod adapter (1/4"-20 female to M6 -1.0 female thread) and President New Virginia antenna, and a Cobra HG antenna with female 1/4"-20 to male M6-1.0 adapter (see photos). Screwed then together and total length is just under 20". The President antenna is not adjustable, so I can't trim it to dial in VSWR. The Cobra is trimmable for VSWR. What do you all think? Will they work (< 1.5 to 2.0 VSWR?). The tripod adapters are the big unknown, only a half inch or so thick, but it may throw everything else off. I need to remove powdre coating in the threads, so they conduct current. Currently no continuity with VOM.

I have a Laird C27S for highway driving, but I need something short like this to get into and out of my garage each day and airport parking decks (96" max vehicle height) when driving around town. Distance communication not an issue in town. But, I'm betting installing this in the center of the roof of my vehicle on an NMO mount will give adequate reception in town (2-3 miles). Hoping it works. Let me know what you think.

 

[slowmover]

That's the same document I posted in message #5.

I should have appended that the k0bg site is a great reference.

.