Building the G5RV: Length of ladder line?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KK6WPX, Jun 7, 2018.

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  1. KK6WPX

    KK6WPX Ham Member QRZ Page

    The items I will use is,
    • 450 ohm ladder line
    • 14awg stranded copper insulated wire
    • SO-239 Connector
    I read that the length of each leg should be 51ft. Now this is where I need help. I have seen plans for this build that calls for anywhere from 32ft all they way up to 40 and 50ft.

    Is the length of the ladder line important? Should it be at least a certain length?
     
  2. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    The length of the ladder line should be close to 1/2 wave on 20m for a true G5RV using a 102 ft. flat-top, such as you are building. The length is important, as it acts as an impedance reflector on 20m, and a transformer on other bands.

    Start with 32 ft. for the ladder-line, which is what most people use, and check your SWR curves. If they are way off from what you would usually expect, add a few feet. But make sure you understand what kind of SWR ranges to expect!

    [​IMG]

    (From W5DXP)
     
  3. W5DXP

    W5DXP Ham Member QRZ Page

    The design specs for a G5RV will work for any frequency.

    The doublet is 1.5 wavelengths in length on the design frequency.
    For 14.2 MHz, the doublet is 1450/14.2 = 102 feet.

    The tuned feeder is 0.5 wavelengths on the design frequency.
    For 14.2 MHz, the tuned feeder is VF*492/14.2 = 31 ft for VF=0.9
     
    N2EY likes this.
  4. KU3X

    KU3X Ham Member QRZ Page

    Why not build a better antenna? How about an 80 meter doublet feed with all parallel feeders right to the tuner. By far it's a much better antenna.

    Barry
     
    AI3V and KC8VWM like this.
  5. W5DXP

    W5DXP Ham Member QRZ Page

    N2EY likes this.
  6. G3YRO

    G3YRO Ham Member QRZ Page

    Yes . . the G5RV (orZS6BKW) is such a poor compromise antenna ! I've never understood why so many people use one.

    If you want an antenna that covers 80 to 10m that will give you a pretty good match on all the main bands, then a W3DZZ is a MUCH better option !

    It's no longer than a G5RV . . . but unlike a G5RV, it's actually RESONANT on all the main bands, so you can feed it with coax all the way to the centre.

    Roger G3YRO
     
  7. KK6WPX

    KK6WPX Ham Member QRZ Page

    Does the W3DZZ require a tuner?
     

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