Mounting NMO antenna to aluminum truck cab?

[JohnDeere7920]

Hey everyone. Had a quick question about using one of the dreaded magnetic hockey puck NMO mounts in my 17 F350 which is of course aluminum. Obviously magnet won’t stick to the top of the cab so I’ve put some felt down with double sided tape to stick it there for my ground plane. 
 

question is the felt and double sided tape interfering with good grounding of the antenna? I really don’t want to screw anything through the top of my cab to secure the antenna mount to. Right now radios work in excess of 5 miles but if somehow fixing this would get me some more miles that would be great. I don’t have an SWR meter to check any of the specifics. Just bought MXT500 radios for farm use so communicate is kinda important at times. 
 

what’s everyone done to remedy the aluminum cab issue? Thanks I’m new here btw so bear with me as I learn these things. We’ve had business band radios for years but they have stopped working and now going another direction since we can’t fix and program our own radios. 
 

WSJV395

[amaff]

11 minutes ago, JohnDeere7920 said:

Hey everyone. Had a quick question about using one of the dreaded magnetic hockey puck NMO mounts in my 17 F350 which is of course aluminum. Obviously magnet won’t stick to the top of the cab so I’ve put some felt down with double sided tape to stick it there for my ground plane. 
 

question is the felt and double sided tape interfering with good grounding of the antenna? I really don’t want to screw anything through the top of my cab to secure the antenna mount to. Right now radios work in excess of 5 miles but if somehow fixing this would get me some more miles that would be great. I don’t have an SWR meter to check any of the specifics. Just bought MXT500 radios for farm use so communicate is kinda important at times. 
 

what’s everyone done to remedy the aluminum cab issue? Thanks I’m new here btw so bear with me as I learn these things. We’ve had business band radios for years but they have stopped working and now going another direction since we can’t fix and program our own radios. 
 

WSJV395

Remember that 'ground plane' isn't the same as electrically grounding something. You need a big piece of metal for the signal to bounce off of, you don't need the antenna to be electrically connected to the panel.

I don't know that I'd trust double sided tape on the exterior like that, but OEMs hang body panels off with that stuff now so what do I know 

[JohnDeere7920]

18 minutes ago, amaff said:

Remember that 'ground plane' isn't the same as electrically grounding something. You need a big piece of metal for the signal to bounce off of, you don't need the antenna to be electrically connected to the panel.

I don't know that I'd trust double sided tape on the exterior like that, but OEMs hang body panels off with that stuff now so what do I know 

Well that does make sense now that I think about it! I just assumed in order for it to bounce off and receive it would need to have a direct mechanical bond to the plane. So I should be good there. Now maybe I need to investigate the combine mounting because I’m not sure that the fiberglass rooftop that the NMO is mounted to there is a good option. I’m sure they have a ground plane under it but I would think a metal surface up top would be better

[SteveShannon]

1 minute ago, JohnDeere7920 said:

Well that does make sense now that I think about it! I just assumed in order for it to bounce off and receive it would need to have a direct mechanical bond to the plane. So I should be good there. Now maybe I need to investigate the combine mounting because I’m not sure that the fiberglass rooftop that the NMO is mounted to there is a good option. I’m sure they have a ground plane under it but I would think a metal surface up top would be better

There are adhesive back steel plates that can be bonded to a fiberglass surface to provide a decent ground plane. 

[WRUE951]

19 minutes ago, SteveShannon said:

There are adhesive back steel plates that can be bonded to a fiberglass surface to provide a decent ground plane. 

i'm thinking i would use this on the Ford Aluminium Cab.  Even on steel made bodies.  My Ram is steel tin and it aint' the asme steel tin cars used in the day, stuff now is  Very flimsy 

[WRXB215]

32 minutes ago, WRUE951 said:

stuff now is  Very flimsy 

Yep, just look at it wrong and it dents.

[gortex2]

My solution was a NMO mounts thru the roof. Had 6 on my 2018. 

 

 

[JohnDeere7920]

39 minutes ago, gortex2 said:

My solution was a NMO mounts thru the roof. Had 6 on my 2018. 

 

 

Do you remember where you got those mounts at? They look clean and I’d only need one. Any issues with water infiltration in the cab after install?

[JohnDeere7920]

8 hours ago, SteveShannon said:

There are adhesive back steel plates that can be bonded to a fiberglass surface to provide a decent ground plane. 

I’ll see if I can find something like that I think it would help a lot. I did screw a 12 inch diameter pizza pan to the combine fiberglass roof and ran a grounding cable to the frame of the combine to try to limit noise. Farm equipment has so much interference it’s insane. If counterpoise truly means anything to these radios it would be a nightmare to bond anything on the machine

[Northcutt114]

1 hour ago, gortex2 said:

My solution was a NMO mounts thru the roof. Had 6 on my 2018. 

Maybe it's just early and I'm not sufficiently caffeinated, but...six? Does that mean you had six different antenna on your truck? Which would mean that you had six different radios in your truck? What could possibly be the reason to have six radios in your truck?

 

[WSJW650]

If through the roof NMO mounts are not desirable; I would do something like this. 
 

 

[WSJW650]

If the tool box itself is aluminum, bolt on or 3M 5200 a round piece of ferrous steel on top of the tool box. 3M 5200 is permanent. 

 

 

[nokones]

Or a glass-mount antenna.

[WRTC928]

How about something like this Larson bracket?

[SteveShannon]

2 hours ago, JohnDeere7920 said:

I’ll see if I can find something like that I think it would help a lot. I did screw a 12 inch diameter pizza pan to the combine fiberglass roof and ran a grounding cable to the frame of the combine to try to limit noise. Farm equipment has so much interference it’s insane. If counterpoise truly means anything to these radios it would be a nightmare to bond anything on the machine

Unfortunately none of these are John Deere green: 

17.5inchX11.5inch Large Stainless Steel Plate for Magnets, 3M Adhesive Back, Mounting Screws, Ideal for Magnetic Shelf, Spice Holders, Fridge Magnets. Mount Anywhere! (Silver, 1 PACK) https://a.co/d/7FDxliM

[WRUU653]

I’ve seen these discussed here on the forum, they are definitely pricey but it’s an option.

Third Brake Light Antenna Mount - 2017-2025 Ford Super Duty

 

[WRYZ926]

You will be better off tuning a non ground plane antenna with those third brake light mounts as you will only be getting a good ground plane in front of the antenna.

My 2010 F150 is all steel but it is pretty thin. The mag mount will hold the Comet 2x4SR at highway speeds but even a small tree branch will knock it off. I will definitely look into adding reenforcement of some type when I finally decide to drill for a permanent NMO mount.

[amaff]

2 hours ago, WSJW650 said:

If through the roof NMO mounts are not desirable; I would do something like this. 
 

 

I like that solution a lot. That, and hood / fender mounts. Yeah yeah they're not "ideal" but they work fine for everything I use them for.