Mobile antenna options for my carbon fiber chassis car (BMW i3)

Discussion in 'Mobile Radio Systems' started by KM6UOZ, Nov 9, 2018.

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  1. KM6UOZ

    KM6UOZ Ham Member QRZ Page

    So as the title suggests I am wanting to install an icom dual band 50 watt mobile radio into my wife's car. This seems very straight forward however she has a BMW i3. For those of you that do not know the chassies of the vehicle are all carbon fiber like a Lamborghini Aventador or an aircraft. So mag mount antennas will not work at all there is no metal to stick to. The Panels of the car the trunk hood and hatchback are a polymer plastic of somesort so they do not dent.

    Any way in this scenario what kind of antenna do you guys recommend for a dual band set up? I thought about doing a glass mount antenna but have read any type of window tinting will be a problem and you cannot use one with even factory tinting. Well, unfortunately, all the rear windows are factory tinted so that option is out. SO then I was debating doing a lip mount antenna on the rear hatch which seems like it would work well however I have read that those mounts use a pointed set screw to lock them in place and make a good connection to the metal of whatever they are connected to, to form the ground plane. In this case the panels are not metal so I would not have a ground plane. What are my options at this point for an antenna with decent performance really appreciate any recommendations you guys with way more experience might have.

    I can't put some huge ugly looking contraption on the car she would object but is okay with 3 to 4-foot antenna. DO they make an antenna with built-in ground plane for mounting on a car?

    Thanks in advance

  2. K0BG

    K0BG Platinum Subscriber Platinum Subscriber QRZ Page

    About the only thing you can do is provide a ground plane using some 3M, 1181, copper foil tape. You can buy it on eBay as cheaper than anyplace. However... Finding a good place to mount an NMO is another issue on the i3 due to the design of the boot (trunk) as it were.

    It is indeed unfortunate, but the i3 is only the tip of the iceberg. If it isn't the lack of a ground plane, it is the huge amount of RFI from the on-board digital electronics keeping us from enjoying our hobby. In fact, some vehicles produce so much RFI, even FM isn't usable. And we need to remember, that passenger vehicles are exempt from Part 15.
    KB0MNM likes this.
  3. KB0MNM

    KB0MNM Ham Member QRZ Page

    You may want to research the foldover antenna systems made to work with mini-vans and such, the Model K5000 mount comes to mind. According to Diamond, there are various types of antennas made to work with compromised ground planes. According to an old pro at Radio City ( maybe closed now, previously in Mounds View, Mn.- associated with Lentini- ads in QST ), the important factor is wavelength. So if you are choosing a dual-band antenna, the SG-7500 might qualify- yet height can be an issue due to parking garage clearances, etc. While there is no particular need to use a foldover system with these so-called 'no ground plane connection' antennas, there is also probably no need to select only Diamond for a supplier. Yet they do provide extensive information in QST magazine ads and on the website. I also have a few cautions regarding maintenance of the electrically actuated foldover mounts. They do not always necessarily provide for extra antenna life... because if you forget or they slip... one slip is enough- they can be up when you think they are down.
  4. KD8DEY

    KD8DEY Ham Member QRZ Page

    Last edited: Nov 11, 2018
  5. KE5PPH

    KE5PPH Ham Member QRZ Page

  6. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    FAA recommended method for installing a whip antenna on non-metallic surface using foil ground plane. Advisory Circular 43.13.

    KX4O likes this.
  7. W6BWH

    W6BWH Ham Member QRZ Page

    The Diamond NR770s are a radialess design. If you can get it on there it will work pretty well. There are a few different options of connectors and colors.
    KX4O and AG6QR like this.
  8. WB8NQW

    WB8NQW Ham Member QRZ Page

    Check out the March 2018 edition of QST page 37. In the antenna forum someone used it on a non metal vehicle.

  9. N7WR

    N7WR Subscriber QRZ Page

    Given as much glass as that car has and the fact that the body is non metalic if it were me I would put a flat metal plate (such as an extra large pizza pan) on the floor behind the back seat, use a mag mount on it, and the antenna of your choice. You might not want to operate if people are sitting in the back seat close to the antenna. If you need to haul something in the cargo space behind the back seat you can always move the mag mount and antenna out of the way.

    An antenna inside the vehicle (even an all metal one) is not unheard of. When (I am a former LEO) we were working undercover in non-descript vehicles we would put a metal plate on the package tray by the rear window and mount an antenna there. With a tinted rear window it could not be seen from outside. It wasn't great but it worked. Should work fine for you since you have no metal to shield in/out signals.
  10. K0BG

    K0BG Platinum Subscriber Platinum Subscriber QRZ Page

    Good suggestion? Not really! The vehicle has passivated glass which speak volumes.

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