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What kind of antenna would be used for 2-meters SSB mobile operation?

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by KC0BUS, May 28, 2019.

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  1. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    You're confusing "earth ground" with the ground plane provided by your vehicle, which is much smaller and actually doesn't matter much in this case. Remember the "ground" around an antenna extends for several wavelengths, not just what's directly under it.

    Only way to determine the effect is with a field strength meter. It's a real eye-opener. A horizontal halo, loop, turnstile, Big Wheel or whatever mounted just 6" above the roof of a van produces most of its radiation to the sides, towards the horizon. I remember when Cushcraft did all their tests on the "Squalo" which came with 6" standoffs and suction cups to mount it to a vehicle roof, and that was before computer simulation and modeling.

    Very effective. Strong horizontally polarized signal just 15-20 degrees above the horizon, which is about where you'd want it to be, to launch above other nearby vehicles; not much "straight up" at all.

    They published those field trials with calibrated F/S readings back in about 1965 or 66.
     
    WA3GWK likes this.
  2. WA2CWA

    WA2CWA Ham Member QRZ Page

    I built myself a 2M turnstile antenna using drill rod, 1 inch round wooden dowel, and the magnetic end of an old discarded speaker.
    I threaded the drill rod on one end, tapped 4 holes 90 degrees apart on the wooden dowel so that the drill rod would screw into the holes. Two nuts, along with a solder terminal, on each threaded end, provided the connection for each dipole element. Bottom of wooden dowel was tapped, magnet bottom speaker bracket was drilled for a clearance hole and a screw held the wooden dowel in place.
    Worked great for many years although my wife would not ride in the car with the antenna in place. :p

    [​IMG]
     
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    That not only works quite well (and hams have been using 2m turnstiles for mobile work since forever), but has an added advantage: While producing a horizontally polarized signal towards the horizon, it produces a circularly polarized signal aimed "up" as well, making it pretty useful for satellite work.
     
  4. KG5RZ

    KG5RZ Ham Member QRZ Page


    Were we talking about mobile hf, but the question was about VHF.
     
  5. KC0BUS

    KC0BUS Ham Member QRZ Page

    Are there any commercial-made halo antenna's for 6-meters or 2-meters ?
     
  6. KC0BUS

    KC0BUS Ham Member QRZ Page

    What are the performance characteristics differences between the halo, squalo and turnstile antenna's? Why would I choose one over the other?
     
  7. KC0BUS

    KC0BUS Ham Member QRZ Page

    Thanks. That's a squalo, I'm currently looking 'halo's'.
     
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Yes, I know.

    The answer applies to VHF also.

    The "real ground" under a 2m antenna extends out to about 40 feet around the antenna (even for a horizontally polarized antenna) so most of what a 2m halo (or whatever) sees as ground isn't what's directly under it.

    For a vertical, the most important image plane extends only to about 20-40" radius around the base of the antenna; but for a horizontal antenna, the reflection plane isn't what collects energy nor conducts current as the "other half" of the antenna like it does with a ground plane or unipole -- it doesn't need that as all the current is pumped into the antenna itself, whether any part of it is grounded or not. It collects or reflects energy to or from the antenna based on multiple reflections within several wavelengths.

    It's very different.

    Try an experiment with a field strength meter placed 10 wavelengths away (only about 65 feet, so this is pretty easy on 2m).
     
  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    They work exactly the same way; so does the PAR Omni-Angle which is a horizontally polarized antenna having three sides. I've tried square, circular and OA-144 3-sided for mobiling and frankly the OA-144 generally outperforms the other two designs for some reason.

    http://www.parelectronics.com/omnis.php
     
  10. K5VZD

    K5VZD Ham Member QRZ Page

    I agree .. However If all you have is a mag mount vertical... don't let it stop u from hollerin cq
    tom
     

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