antenna phasing stubs

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KC0BIN, Feb 13, 2018.

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  1. KC0BIN

    KC0BIN Ham Member QRZ Page

    I've cobbled together a monstrosity from lengths of coax I had at hand. Just a prototype/design test. If the design proves out I'll rework it with quality components (CopperWeld or FlexWeave, etc.) and a quality 6:1 current balun.

    The antenna is a 3-element (3x half-wave in phase) collinear dipole, cut for 50.000MHz; I'd rather tune it with capacitive reactance than inductive.......good quality roller inductors are getting impossible to find (even Fair Radio is sold out of most of theirs!)

    Anyway, is there any reason why I shouldn't use 450-ohm window line for phasing stubs? Or 300-ohm twin-lead?

    Parallel line is very handy for phasing stubs; it couldn't get any easier. But, this is a VHF antenna and I suppose it's possible that some type of twin-lead or window line might not cancel due to conductor spacing.

    Paranoia or real concern?
     

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  2. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Should work fine, but how will you rotate it? Or are you just looking for two directions?
     
    KC0BIN likes this.
  3. KB4QAA

    KB4QAA XML Subscriber QRZ Page

    Balanced line works perfectly fine for phasing.
     
    KC0BIN likes this.
  4. KC0BIN

    KC0BIN Ham Member QRZ Page

    For the beam, I first string nylon line between two trees with the EZ-hang system. Midpoint of this line has a bearing connection to the center-of-gravity of the antenna, allowing it to rotate freely in azimuth. The coax N-connector is located at the center-of-mass, too, pointing straight down. A very light nylon line (surplus military parachute cord) threads right through the boom, both ends anchored on the ground with tent stakes for which azimuth I want. Mad Scientist stuff to be sure, but it does work! The "steering cord" can also be threaded through one of the director elements, too, though I prefer fishing line.

    For a wire antenna, I just string it from NE to SW and leave it at that.

    I run my radio in the vestibule of the tent along with the battery, tuner & whatnot.

    TNX for the replies WB2WIK and KB4QAA!
     
    NH7RO likes this.
  5. W5DXP

    W5DXP Ham Member QRZ Page

    The spacing of 450 ohm ladder-line is close to 1% of a wavelength on 2m. I would go with 300 ohm twinlead for the stubs.
     
    KC0BIN and KD0WQP like this.

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