Six meter colinear

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by N5MRG, Nov 25, 2009.

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  1. N5MRG

    N5MRG Ham Member QRZ Page

    A few years ago I had access to an antenna test range and designed this for repeater use. It tested a few db gain over the DB Products folded bay that we used at the time.

    It is a 5/8wl over a 3/8wl and provides a very narrow beamwidth at the horizon due to the phasing of the elements.

    The top section is roughly 142" long, bottom section is 86" long. The phase correction between the two elements is a loop 10" in diameter. (Think Ringo)
    Use a fiberglass rod as an insulator and space the two elements approx 4". Four horizontal ground radials 58" long are required.

    The feed poind is 50 ohms and I used a qtr wave stub of RG58 to provide DC ground.

    In most cases this antenna can be built from a salvaged 11 meter half wave GP. There should be enough aluminum tubing.

  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Are you going to publish the diagram for this, or what was the post about?
  3. N5MRG

    N5MRG Ham Member QRZ Page

    Sure... you want me to build it for you as well. :rolleyes:

    All the info was given to be able to construct the antenna if you passed the test.
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I believe I did pass the test but the info provided doesn't model well.

    This would be 0.66WL over 0.4WL with a .145WL phase shift network, which is 52.2 degrees (all assuming Fo = 52 MHz).

    That wouldn't yield a good antenna, nor one with a 50 Ohm feedpoint.

    If you didn't use a matching network (other than a shorted 1/4-WL stub across it, which doesn't change impedance much) I don't see how this worked.

    That's why I asked for more information; it seemed either something's missing or if it really matched well that would be due to feedline loss created by the major mismatch.
  5. K7JEM

    K7JEM Ham Member QRZ Page

    Just a cursory glance makes me think it would look OK at the feedpoint. It would be very close to 5/4 wavelength, electrically, depending on frequency used.

    I see the phasing section as being closer to .19 wave.

    .66 + .4 + .19 = 1.25

  6. N5MRG

    N5MRG Ham Member QRZ Page

    Then I'd suggest you got to the effort to build one and see for yourself.

    The test range data we have speaks for itself. As well as the one that has been in use on the repeater for the past few years.

    Of course... they told me I could not 500khz duplex a lowband micor, duplexer, PS, controller and link radio all in a five foot rack either. :rolleyes:
  7. N5MRG

    N5MRG Ham Member QRZ Page

    Yes Joe, The return loss is very good.
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Yeah, and bumblebees can't fly, either, so I know about that.:)

    Rather than build such a big antenna for range testing, I can scale it down to 150 MHz and make a 1/3-size model, then test it here.

    Now all I need is a few more Round Tuits.:p
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