9:1 or 49:1 for end-fed long/random wire

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by HA6AN, Oct 15, 2019.

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  1. HA6AN

    HA6AN QRZ Member

    Hi guys,I need some advice as an antenna newbie :D
    Before my house was built next to the older one and moved in,I used to have a 30m long long/random wire antenna.It was fed pretty "ghetto" way,with a simple speaker wire as a twinlead,and the house's metal gutter as the counterpoise.
    Now in the new place,I can stretch out the old 30m wire to about 40m,and I would like to feed it with something better.The old twinlead was a bit too hard to match(tho I could do it more or less 80-10meters,with a beefy tuner),so I would like to add an unun.The radiating part would be the 40m long wire,the counterpoise could be the new and bigger gutter,or I can throw down another wire from the roof.
    The question is:which unun would be more ideal?a 49 to 1,or a 9 to 1?The goal would be to have a not efficient but usable antenna 80m to 10m,until I can put up other and better antennas for the lower and higher bands.
    Sorry for this short "novel" I wrote,I hope everything is understandable :D
    Thanks in advance,73!
     
  2. K7TRF

    K7TRF Premium Subscriber QRZ Page

    If you'll use a half wavelength of wire on the lowest band of operation such as 65 feet for 40m and higher frequencies or 125 feet for 80m and higher frequency operation then use a 49:1 or 64:1 matching transfomer and only a short piece of counterpoise wire that's approximately 5% of a wavelength on the lowest supported band.

    If you'll use other lengths of wire that don't happen to be halfwave resonant on your lowest operating band then use a 9:1 transformer and use some decent ground radials or counterpoise.
     
    KD9LVR, KU3X, N8ZL and 1 other person like this.
  3. WA7ARK

    WA7ARK Ham Member QRZ Page

    @HA6AN, As Dave says, there are basically two kinds of so-called "end-fed" wire antennas that are popular nowadays. I recently wrote this explanation of the differences between them. That forum thread goes on to a proposed 40m up Hertz solution for G8GYW.

    Since you want to start on 80m, look at the commercial EFHW-7510-2k or
    HyEndFed_8_Band. It is possible to homebrew these, so write back if you need help with that.
     
    Last edited: Oct 15, 2019
    N8TGQ and K0UO like this.
  4. G8GYW

    G8GYW Ham Member QRZ Page

    Having initially tried a random wire with 9:1 unun I can verify that Mike's solution is much more successful. Here's the VSWR plot across four bands.

    antenna.png
     
    K9UR likes this.
  5. 2M0VZX

    2M0VZX Ham Member QRZ Page

    Isn’t it 127ft?
     
  6. K7TRF

    K7TRF Premium Subscriber QRZ Page

    That depends on the specific 75m/80m center frequency you're trying to achieve, longer for CW and bottom of the 80m band emphasis, shorter for 75m and top of the SSB band emphasis. But yeah, there are a lot of commercial EFHW designs based on 127 feet and the use of compensating coils and compensating capacitors in the matching transformer to deliver best multi-band performance.

    I guess I should have added the word 'approximately' to the numbers above as it's not intended to be a design recommendation just a description of approximately how long an EFHW has to be to support a certain low frequency band.
     

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