NMO mount options for glassroof...could use some help

[radioclicks]

I don't know what I was thinking but I said yes to one of the kid's school project and now here I am, seeking help to save my ass, and probably kid's street cred.

What I am trying to do:
Run an ADS-B receiver and an ATC (airband) scanner in my 2022 Tesla Model S (glassroof/aluminum body etc) in a middle school parking lot, once/month for 6 months. The car will be stationary in the parking lot, so the antenna/mount won't be moving at all. The kids and their parents will be learning about some basic aviation/atc concepts.

Antennas:
* ADS-B Double 1/2 Wave Mobile Antenna (link)
* VHF Air (118-136 MHz) 1/4 Wave Mobile Antenna (link)

Where I am lost:
* I'm not necessarily new to scanning but definitely new to car mounts and didn't realize the NMO mounts need grounding plane, the whole shebang.

Some of the options I've looked at:
* Get some sort of a suction cup mount I can stick on the glassroof, but I can't figure out how I'd go about adding some sort of grounding plane to these suction cups, and then adding the antennas/mounts.
* I read a review somewhere (can't remember where) that someone was able to install similar antennas on a fibreglass roof with a 6061 aluminum sheet, but then again, I couldn't find much info.
* I was also thinking of maybe getting a magnetic strip/sheet that I could stick to the roof and then have the antenna stick on top?

What I need help with:
* Given my car's glassroof and aluminum body, and antennas I've got, what kind of mounting options I have? The solution doesn't need to be permanent, just temporary, and as I mentioned earlier, the car will always be stationary.

Many thanks in advance for all your help. I got myself in this situation, not necessarily by choice, but yeah, please help.

 

[trentbob]

I don't know what I was thinking but I said yes to one of the kid's school project and now here I am, seeking help to save my ass, and probably kid's street cred.

What I am trying to do:
Run an ADS-B receiver and an ATC (airband) scanner in my 2022 Tesla Model S (glassroof/aluminum body etc) in a middle school parking lot, once/month for 6 months. The car will be stationary in the parking lot, so the antenna/mount won't be moving at all. The kids and their parents will be learning about some basic aviation/atc concepts.

Antennas:
* ADS-B Double 1/2 Wave Mobile Antenna (link)
* VHF Air (118-136 MHz) 1/4 Wave Mobile Antenna (link)

Where I am lost:
* I'm not necessarily new to scanning but definitely new to car mounts and didn't realize the NMO mounts need grounding plane, the whole shebang.

Some of the options I've looked at:
* Get some sort of a suction cup mount I can stick on the glassroof, but I can't figure out how I'd go about adding some sort of grounding plane to these suction cups, and then adding the antennas/mounts.
* I read a review somewhere (can't remember where) that someone was able to install similar antennas on a fibreglass roof with a 6061 aluminum sheet, but then again, I couldn't find much info.
* I was also thinking of maybe getting a magnetic strip/sheet that I could stick to the roof and then have the antenna stick on top?

What I need help with:
* Given my car's glassroof and aluminum body, and antennas I've got, what kind of mounting options I have? The solution doesn't need to be permanent, just temporary, and as I mentioned earlier, the car will always be stationary.

Many thanks in advance for all your help. I got myself in this situation, not necessarily by choice, but yeah, please help.

So you're going to get a lot of feedback from more experienced people than me and I am at a disadvantage as not a fan of EV's and I don't see the same future that some do.. looked at your car for the first time and still can't really figure it out but..

There's no problem using aluminum as a ground plane but you do have to be concerned with Integrity of the metal, it's not like steel, I looked at a 360 view of your car which didn't help me that much but is there any chance of drilling a hole? And is there anywhere you think you might be able to use a NMO lip mount?

 

[radioclicks]

Hey, thanks for the reply and I appreciate the questions; if nothing else, they'd probably force me (or others to look at this situation from a different perspective)

but is there any chance of drilling a hole?

Unfortunately no. If I needed a more permanent solution then thats something I would've considered, but its literally only for 6 months (once/month middle school club meeting), so can't really justify drilling.

And is there anywhere you think you might be able to use a NMO lip mount?

The ones I looked at on Amazon, they all seem to scratch the body/paint, so trying to avoid that.

 

[Randyk4661]

Since the car won't be moving during the demonstration, The 1/2 wave really shouldn't need a ground plane.
For the other antenna, get a mag mount for each and just set it on top of the glass roof. If you really want a better ground plane, place the antenna on a large cookie sheet or pizza pan on the roof. It won't look the greatest but it should work for you.
Remember to remove before driving.
Any placement outside the car should work for reception.
If you want to make the antennas permanent, that will be a challenge

 

[radioclicks]

If you really want a better ground plane, place the antenna on a large cookie sheet or pizza pan on the roof.

Thank you; both the antennas come with their mag mounts, so that's a good thing. Now, if I wanted to use an aluminum sheet as ground plane, is there a minimum size it would need to be?

And in terms of the setup, am I correct in understanding that this sheet will go on glass roof, then the mag mount on this sheet, and then the antenna on the mag mount?

 

[trentbob]

@radioclicks I understand about the possible damage from the lip mount, it's usually not a problem but then again, aluminum and a Tesla paint job is an unknown, the real damage done by lip mounts is hidden and done by the lower lip where the coax protrudes, you'll often see rubber waterproof insulation get torn up causing leaks.

Randy's idea sounds good, some people use pie plates.😉

 

[Randyk4661]

Thank you; both the antennas come with their mag mounts, so that's a good thing. Now, if I wanted to use an aluminum sheet as ground plane, is there a minimum size it would need to be?

And in terms of the setup, am I correct in understanding that this sheet will go on glass roof, then the mag mount on this sheet, and then the antenna on the mag mount?

I don't believe there is a size for the metal pans that need to be used. If anything the larger the better(?) Since they are receive only, you can place the antennas close together or spread them apart if you want.
The setup is correct, place the pan on the roof, then the mag with antenna on the pan.
You can place rubber feet on the pan or cloth between the glass and pan to prevent scratches without effecting the reception.
It seems to me I read where someone used a stainless steel serving tray once because the mag mount stuck to it. This was a long time ago, don't remember for sure.


Experiment at home before trying at the school,

 

[trentbob]

I don't believe there is a size for the metal pans that need to be used. If anything the larger the better(?)

Yep, I can remember in the old days using file cabinets, worked great.

 

[radioclicks]

Thank you guys!!! Exactly the info I was looking for. Again, I appreciate the help. Once I have everything setup and ready to go, I’ll report back with photos.

 

[mmckenna]

Thank you guys!!! Exactly the info I was looking for. Again, I appreciate the help. Once I have everything setup and ready to go, I’ll report back with photos.

There's a couple of things you need to consider here:

1. DPD antennas are way overpriced. $87 for a mag mount 1/4 wave VHF antenna is highway robbery.

2. The 1/4 wave VHF antenna will want a ground plane under it if you want it to work to its full potential. It will work without one, but it'll work better with one. The ADS-B antenna is 1/2 wave, so it does not -require- a ground plane, but will work better with one.

3. If your car is not moving, and this is just a demo set up in a parking lot, there's really no reason to mount this on your car. The Tesla Model S (my sister has one) doesn't have a lot of room to mount antennas, unless you go on the trunk, but again, if you are just sitting in a parking lot, no need to drill holes or do mag mounts.


It's easy enough to set up a temporary pole to hold the antennas. That could be as easy as a 1 gallon bucket with a piece of pipe stuck in it and filled with fence post concrete.

A simple 1/4 wave antenna is cheap. Add a ground plane kit and you're all set. You can make your own really easily if you have some soldering skills, or you can just buy the parts and put it all together:

For VHF, this antenna, cut to length for the air band (cutting chart is included): Larsen NMOQ88C 88-136 MHz Field Tunable 1/4 Wave Mobile Antenna NMO Type
For the base adapter (provides the ground plane) Mobile Antenna to BASE Convertor VHF UHF Antennas TE Connectivity MBC

For ADS-B, this antenna, https://www.amazon.com/AirNav-ADS-B-Outdoor-Antenna-Connector/dp/B07K7YW1XJ

You'll need some coax for the VHF antenna, and some hardware, but that should all work well without having to molest your car with antenna mounting.

If you really want to mount antennas on your car, we're happy to help, but doesn't seem like that's what you really need?

 

[hazrat8990]

https://www.amazon.com/gp/product/B0744Q3RDM/ref=ox_sc_act_title_2?smid=AA3MGRC7F9EI2&th=1 is another option for a ground plane. Something like that mounted to a painter's pole would work decent.

 

[rgchristy]

This might be a bit further outside of the box than you had in mind, but it seems like you are only using your EV to power the ATC scanner.

Perhaps you could do like a ham radio Field Day outdoor setup. The school probably has tables and even a gazebo-like tent. The power could come from either a generator or portable solar panels. Even a long extension cord would work. You could use a selfie tripod to anchor the antenna.

This way, everyone wouldn't be standing around the Tesla trying to look at your scanner and possibly scratch the paint.

All of this would be weather-permitting, though. I'm sure that the Tesla idea would be, too.

Just a thought....

 

[JustinWHT]

Where I am lost:
* I'm not necessarily new to scanning but definitely new to car mounts and didn't realize the NMO mounts need grounding plane, the whole shebang.

All antennas need a ground plane (excluding some special ones), specifically for proper match to transmitter. But you're using it for a receiver so its not that necessary. Likewise an 18" VHF whip (152-158 MHz) would work for aircraft frequencies.

Magnetic mounts obviously won't work on an aluminum body.

1st idea - Cookie baking sheet, Walmart $6, 17"x11". NMO mount with 15' coax with PL-259 connector, $25. 18" OEM whip, $15

2nd idea - Same cookie sheet, $6. PL-259 plug and SO-238 socket, 20" coat hanger soldered into plug, hot glue or epoxy.

Couple of 2"x1" wood blocks hot glued to cookie sheet, couple of lines of hot glue on bottom of blocks again against car frame to keep from scratching. Something to weigh down cookie sheet in the wind.