Hidden 2m mobile antenna?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W8UNX, Apr 1, 2010.

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  1. W8UNX

    W8UNX Ham Member QRZ Page

    I am wanting to install my TM-D700a in my Dodge Magnum, but, for various reasons which we will just shorten to the variable "XYL," mounting a 2m/440 antenna anywhere on the (outside of the) car is a non-starter. Initially, I thought about laying some stiff copper wire in the rain channel on the roof, but that would be darn near horizontal and not likely very useful for 2m repeaters, I'd think.

    In searching the interwebz for ideas, I came across this:

    STI-CO Covert VHF Bumper Antenna

    It consists of a pair of dipole antennas and a coax splitter. The instructions (available elsewhere) show one dipole mounted at the front left corner and one at the rear right corner. The leads are then plugged in to the coax splitter (more of a yoke, really) and then from there in to the radio. $350 seems like a lot for a couple of dioples and a coax section, but maybe I'm overly-frugal.

    So, I'm thinking of building something similar and giving it a go. Before I do, though, I thought I would ask here and see if anyone has done something similar, or maybe has experience with the STI-CO product and can advise on how well this is likely to work out.

    Many thanks and 73s,

  2. KA9MOT

    KA9MOT Ham Member QRZ Page

    Last edited: Apr 1, 2010
  3. W8UNX

    W8UNX Ham Member QRZ Page

    But, they do come with a small roll of butyl tape for affixing the antennas to the inside of the bumper. That has to be worth something. ;)

    Yes, I've seen those. They go on the outside of the car which is not going to work if I want to keep the peace. The idea with those STI-CO dipoles is that they attach behind the bumper fascia and are completely hidden. Thank you for the suggestion, though.
  4. K7JEM

    K7JEM Ham Member QRZ Page

    You might be able to tape a QW piece of wire to the inside of a back window, and put radials down, or use the car body for a ground plane. Any sort of inside antenna will be a compromise, but it should work to some extent. Or copper or AL tape on the inside of the window.

  5. KC7YRA

    KC7YRA Ham Member Volunteer Moderator QRZ Page

    My gut feeling is that you would be disgustingly disappointed with the "behind the bumper" antenna. Not only is the orientation wrong, it crams it extremely low on the vehicle and right next to metal. It would "WORK", but my definition of work and yours may be very different. It MAY play on a very local repeater, but that is it.

    This really is an instance where you are stuck with only a few options. Either come to an agreement with the wife about something outside of the vehicle, or don't. Having tried internal antennas and a variety of low profile, homemade versions, I can safely say that you will be disappointed.

    The other concern with anything in the passenger compartment is RF energy frying on you (the passengers) or some of the electronics. Having some vertical separation between you and the antenna is a great help in lessening the RF exposure.

    If you can come to some reasonable compromise in the marriage, you can look at something like this

    They replace the modern "dome" antenna on many modern vehicles. If your car has a similar dome, you could get one of these. That is about as hidden as you are going to get. Or maybe a glassmount.

    Good luck,
  6. KJ4PLT

    KJ4PLT Ham Member QRZ Page

  7. W8UNX

    W8UNX Ham Member QRZ Page

    The hatch window is completely covered in defroster elements and on-glass antenna for the radio. I hesitate to put any antenna inside the car, anyway.

    The bumpers on the Magnum have quite a bit of vertical dimension. I think I could get the driven leg of the dipole mostly vertical, with the ground leg forced horizontal, depending on where behind the fascia I put it (more towards the grille). Of course, then I'm dealing with proximity to the steel beam/channel that the fascia wraps and, because the car rides so low to start with, I'm virtually on the ground with it.

    I suspect you are right. This wasn't an issue when I had a pickup truck and she never drove it and we took her car everywhere. Heh.

    Rest assured, I have no desire to put an antenna inside the passenger compartment.

    They have some interesting solutions. The Magnum doesn't have any antennas on it at all. If it had the Sirius satellite option, it would have one of those little puck antennas. Maybe I could get away with a Fuba-style (European-style) install. Something to think about.

    I worry that the RF won't couple to the outside element, opting instead to radiate all over the inside of the car. Probably irrational and over-cautious, but there you have it. Thanks for the suggestion, though.

    Maybe the Euro-style sloped antenna is the way to go. I'd have to find someone reliable to drill the car, though. Hrmmm.
  8. K9STH

    K9STH Ham Member QRZ Page

    It is possible to use the rear window as a "slot" antenna. The thing about "slot" antennas is that when the "slot" is wider in the horizontal plane the radiated signal is vertically polarized!

    Glen, K9STH
  9. KJ4PLT

    KJ4PLT Ham Member QRZ Page

    i know several people running the through glass antenna and they claim they work just fine but its like anything else, one persons trash is anothers treasure. if you catch my drift.
  10. W8UNX

    W8UNX Ham Member QRZ Page

    You know, Glen, you might be on to something here. Treating the car as a cavity-backed slot antenna hadn't occurred to me. I wonder how the other windows in the car affect the radiation pattern. I could mount a small probe in the center console arm rest to "drive" the cavity. Hrmmm. :eek:
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