Antenna mounting ground plane

Aptera Community Aptera Discussions Antenna mounting ground plane

Aptera Community Aptera Discussions Antenna mounting ground plane

  • Antenna mounting ground plane

     Harry Parker updated 1 week, 4 days ago 10 Members · 20 Posts
  • Dennis Swaney

    Member
    May 7, 2022 at 2:05 pm

    I have a portable XM Radio receiver that I move between my cars so that all have a small magnetic antenna (about 1.5″/40mm) on them. In addition I have CB radios I use with the cars. One CB antenna is a magnet mount K40. I can fabricate steel plates for these but will the frame of the Aptera provide a sufficient ground plane?

  • Len Nowak

    Moderator
    May 7, 2022 at 2:33 pm

    Is that much different than the grounding requirement for all the other electronics in the Aptera?

    Also we leaned then belly will be aluminum for the skin cooling system.

    ( Of course the attached picture of the beta mule has much more metal components that will not be in the production unit)


  • Gary Greenway

    Member
    May 7, 2022 at 4:45 pm

    The belly pan will be aluminum. It may already be DC grounded. For maximum performance run a braided bonding strap from the chassis of your CB radio to the belly pan. This should allow sufficient RF capacitive coupling to ground. The XM ought to be fine.

  • Tim Jorgenson

    Member
    May 8, 2022 at 10:58 am

    Ground planes, when referring to an antenna, is not the same thing as an electrical ground!

    What is Antenna Ground Plane?

    In the case of a non-metallic vehicle, you would probably need to have a special antenna with its own ground plane built in. The size of the ground plane changes depending upon what frequency the antenna uses. Higher frequency, smaller ground plane (think VHF/UHF for satellite) and CB is HF and requires a much larger ground plane. To learn more, look into ham radio related websites.

    • Dennis Swaney

      Member
      May 8, 2022 at 11:05 am

      Correct. I was thinking of getting the tow package and use it as the base for creating a steel platform for the XM & CB magnetic antennas.

  • John Fleckenstein

    Member
    June 16, 2022 at 3:33 pm

    The XM/Sirius antenna may do well on the dash, preserving the aerodynamics…

    As far as Amateur Radio VHF/UHF antennas, the ground plane needs to be ≈ 48cm for VHF and ≈18cm for UHF. Antennas not needing ground planes are usually half wave antennas.

    In roofs of non-metallic materials, I have applied stainless steel tape to build a ground plane. This would be problematic with the solar cells on the roof of the Aptera.

    Not having received my Aptera, I can only suspect that a lip mount antenna with metallic tape under the lip may have to suffice for a ground plane that may be adequate but directional due to the nature of the less than ideal ground plane. Reflected power may also be a consideration.

    The addition of an external antenna will adulterate the aerodynamics. Could an accommodation be made for public safety/amateur radio/specialty antennas within the structure of the vehicle?

    • Dennis Swaney

      Member
      June 22, 2022 at 8:16 am

      Correct. The CB band in these United States has a nominal wave length of 11 meters or 36.09 feet. So those real large CB antennas you sometimes see on Jeeps, pickups are 9 feet or 1/4 wave length. My tunable K40 antenna is 1/8 wave length and the CB splitter I have on my Miata’s stock radio antenna makes it a 1/16 wave length. Thus the need for a ground plane. I’m hoping that the metal framework with the tow hitch attached will be sufficient.

  • Llewellyn Evans

    Member
    June 16, 2022 at 4:35 pm

    You DON’T need a ground plane.

    Use a NGP antenna.

    I use a window antenna for the UHF in my van. It is a film with wiring in it that sticks to the window.

    No hole drilled in the car for cable. No ground plane. Stick it on a surface in a logical spot and you are done.

    https://www.snowys.com.au/on-glass-uhf-cb-antenna-45dbi-gain-ae5004?gclid=CjwKCAjwqauVBhBGEiwAXOepkRMYYrg4LuQbNBuI5Dv5DNpn_I2ZYfmuMSmPi7O67jHiJ8okG5mJ5RoC-YYQAvD_BwE

    • Dennis Swaney

      Member
      June 16, 2022 at 8:33 pm

      You are aware that antenna is set for 477MHz? Just because that frequency is the 17.55th harmonic of 27.185 MHz (Ch 19 mid-point of the 40 CB channels 26.965 – 27.405 MHz) doesn’t mean it will work. Besides, I have my trusty K40 bottom-loaded whip antenna. Mounted on a flat horizontal plate from the tow hitch, the magnetic base & load coil will be slightly below the tail so only about 48″ of the 3/16″ diameter stainless steel whip will be sticking up in the airflow. How much drag will that add?

      Oh, that 477MHz is the 4.9th sub-harmonic of the 2338.75 MHz middle of the XM radio frequency band. Again, that doesn’t guarantee it will work with the XM satellite signals.

    • Llewellyn Evans

      Member
      June 16, 2022 at 8:37 pm

      yep. It was an example.

      Use any other non-dipole that will suite the application and you don’t need a ground plane.

  • David Marlow

    Member
    June 16, 2022 at 11:38 pm

    Sense the Aptera body shell is not metal the antenna could be placed inside. This would also eliminate the air drag that it would cause. Sticking things on the outside of the Aptera that might disturb the air flow around it could be considered an insult to its designers.

    • Dennis Swaney

      Member
      June 17, 2022 at 8:38 am

      Again, I’m curious as to how much drag will be induced by a 3/16″ stainless steel whip.

      • David Marlow

        Member
        June 17, 2022 at 2:16 pm

        That whip has a base and haven’t you seen the whips get bent by the air flow while driving. It may increase the total air drag by 10% as it will not be part of the intended air flow.

        • Dennis Swaney

          Member
          June 17, 2022 at 4:57 pm

          The base will be lower than the license plate so it will only affect the underflow. Besides it will be BEHIND the Aptera body so the airflow will have left the body already. Of course there will be turbulence caused by the whip but I don’t think it will add that much to drag. On other vehicles the K40 would either be in the middle of the roof or at the middle of the front edge of the trunk lid on a convertible. I think those positions would cause way more drag for those vehicles.

  • my_discord_number_is_0328 bloody stupid

    Member
    June 16, 2022 at 11:42 pm

    having a stiff non moving antenna can also function as was for people to see the outer parts of wheel cover, and it should be placed at wheel driver is not near to so he can see it and place it when driving properly. a camera at the top end of it would also allow preserving momentum around a turn or around lanes, looking over most SUV towering in front of you, behind you etc. itd aldo help for parking this big car.

    one reason people buy SUV is for visibility like this. another reason for SUV is assumption that they need all the space when in reality they almost defintly could just use roof rack for unusual times when they could justify need for more storage space. the other reason is precived safetey:youtube channel called “apteras owners club ” did video on crash saftey… its not as simple as “big car= safer because big people and animal and big things generally more durable”, aptera could convince people its just as safe.

  • James Pace

    Member
    June 19, 2022 at 8:57 pm

    I have a ham license but do not presume to know what I am talking about here. But couldn’t the aluminum heat sink above the belly pan serve as an adequate ground plane for an antenna one could mount inside the cab? Does the antenna need to be in contact with the ground plane? I’m thinking a little whip antenna like I use on my handheld. Not a big 12 footer.

    • Gary Greenway

      Member
      June 22, 2022 at 8:50 am

      Yes, it can. The belly pan will be likely aluminum itself. It doesn’t matter if it is wrapped or painted. As long as you run an RF braid (not DC wire) from the transmitter to the belly pan you’ll have a good capacitive coupling to ground. However, if you mount the antenna fore or aft of the belly pan, you can expect a wonky propagation pattern.

      If you mount the antenna inside the cab, it will be partially shielded by the copper backing plates of the solar cells.

  • Harry Parker

    Moderator
    June 25, 2022 at 11:01 am

    Just flagged spam from “Brian Brian” here. Is he a repeat offender?

    • Dennis Swaney

      Member
      June 25, 2022 at 12:14 pm

      msaga gamina above on this thread is another apparent spammer.

      • Harry Parker

        Moderator
        June 25, 2022 at 12:42 pm

        Thanks for the heads up. Just flagged him too.

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