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Question about a dual end fed antenna - possible?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W4LLZ, Aug 5, 2020.

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  1. W4LLZ

    W4LLZ Ham Member QRZ Page

    I have currently an EndFed wire antenna that has a 9:1 UNUN for HF running north to south. Is it possible, reasonable, practical, to connect another wire of same length to the same 9:1 UNUN and have it radiate East and West as well as North and South to get signals in all 4 directions.
    Thanks
     
  2. AB6RF

    AB6RF Ham Member QRZ Page

    Nope, unfortunately that would not work.

    When more than one antennas are connected in parallel, the antenna radiation patterns don't simply get superimposed on top of each other.
    The combined radiation pattern will depend on the phasing of the radiated signals, and if done randomly would most likely create an ugly pattern with peaks and nulls at all kinds of random directions.

    A much better approach would be to put an antenna relay up to the point where the two antennas come together, and feed only one antenna at a time depending on which one gives you the better signal to a given particular direction.
    Each antenna would probably need its own unun, otherwise the relay would need to handle all kinds of high voltages and/or high currents.
    (if the relay is between the unun and the two antennas)
     
    N7EKU likes this.
  3. AK5B

    AK5B Ham Member QRZ Page

    Take your two antenna halves, connect them to a center insulator, attach a feedline, and voila! You have just constructed a Hertz (dipole) antenna.

    Use the formula 468 dived by the frequency in MHz to get into the ballpark for length depending on the band of choice (or use OWL and a transmatch for operation on more than one band otherwise.

    73,

    Jeff
     
    W2VW, KU3X and AI3V like this.
  4. WA7ARK

    WA7ARK Ham Member QRZ Page

    How high is it?
    How long is it?
    What are you doing for a ground-plane/counterpoise?
    How long is the coax?
     
  5. AI3V

    AI3V Ham Member QRZ Page

    What makes you think your half antenna (the other half being every wire in your house) is directional ?

    These kluge attempts at antennas are always a completly random crapshoot.

    Rege
     
    W6MK and AK5B like this.
  6. AI3V

    AI3V Ham Member QRZ Page

    Oh yeah, he's got a counterpoise alright.

    Rege
     
    AK5B likes this.
  7. KB7WG

    KB7WG Ham Member QRZ Page

    A vertical will give you compass coverage.
     
    AK5B likes this.
  8. W4LLZ

    W4LLZ Ham Member QRZ Page

    High: about 50'
    Ground Plane: Its an End Fed, the braid in the Coax is the counterpoise; however i have 2 60 wires connected to the UNUN as well as a counterpoise as well to dissipate the reflective power.
    Coax is 100'.
    Wire is 145'.

    All good - apparently its a "kluge" idea.
     
  9. K9AXN

    K9AXN Premium Subscriber QRZ Page

    The radiation pattern of a 1wl center fed dipole is narrower than a 1/2wl center fed wire. The impedance will be 10,000 Ohms --- calculated using the proportional physical effects of a center fed 1/2wl wires. It can be driven with a link coupled anti resonant tank using a capacitor and inductor with 5000 Ohms reactance; these are a pair of end fed 1/2wl wires which are mutual counterpoises. This makes a formidable antenna needing no other help.

    Regards Jim K9AXN
     
  10. W9XMT

    W9XMT Ham Member QRZ Page

    Below is a NEC4.2 calculation for a typical installation of a 1WL, center-fed, h-pol dipole at 1/2WL AGL.

    The feedpoint impedance for these conditions is outlined there with a red rectangle.

    [​IMG]
     

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