I decided to go ahead and do it .....

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KF4ZGZ, Jan 17, 2018.

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  1. KF4ZGZ

    KF4ZGZ Ham Member QRZ Page

    My antenna plan, that is.
    Just for kicks and grins ........ and personal edumacation.

    I now have crossed 80m dipoles. Same support mast and about a foot apart.
    I am also planning on raising the support at least another 10 feet.
    Dipole 1(old one)- cut for around 3.9mhz. I do the math, cut the wire, use a tuner. Fed with 650-ohm homebrew LL.
    #2 - is basically a random piece of wire ( Hmmmm, That looks pretty long, I'll use it!) ended up around 4.2mhz, fed with 50ft. of 450-ohm LL to a 4:1 balun and coax to the shack. The balun and coax are on the ground.

    #2 has everything going against it and is down about 1 s-unit from #1.
    I expect when I raise everything, and get the feed off the ground, they will be pretty much identical.
    So, I don't need it, but it looks really awesome!

    I'm thinking what I should do is re-cut #2 for 40m, that way I should at least get an advantage out of the antenna there and I should get different radiation patterns when tuned to other bands than the 80m will be on the same bands.

    What think ye, O antenna denizens of the Zed?
    (Just these 2 antennas .... no verts, no inv. L's, no moxons, no spiderbeams, etc.)

    Matt
     
  2. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Since you wrote "same support mast," as in "one" mast, are these inverted vees?

    If so, how high above ground is the center feedpoint?

    80m dipole (or inverted vee) is basically omnidirectional until it's up around 60' above ground or so, so "orientation" hardly matters -- shoot for convenience. If you can get it up >60' above ground, it starts to develop a pattern you'll notice and then orientation becomes more important (but still not very important until it's much higher).
     
  3. KF4ZGZ

    KF4ZGZ Ham Member QRZ Page

    Oh, flat top dipoles. Both center supports are on the same mast. The ends of both are supported by trees.
    Playing with them some this morning I actually did have one guy that was kinda low ... switched to #2 and he came up a couple of s-units.
    My comparisons have been in bypass mode on the tuner.

    But still, I think cutting it for 40m is the way to go.
    That is of the snow will stop and go away!

    Matt
     
  4. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    The nature of propagation.

    Interesting test: Repeat what you describe, but see if the same station's signal fades (maybe a couple of S-units), and then switch back to the other antenna.

    Does the signal come right back up again?

    This happens all the time on HF, unless the propagation is ground wave (which would require the other station to be quite close). If it's ionospheric, the nature of such propagation is that it "rotates" and does not maintain any particular polarity for long, so switching to an alternate antenna during a fade will often bring the signal right back up again, and then when it fades again, go back to the original one...and keep doing that.

    Works great for receiving, but impossible to know "when to switch" when transmitting.

    Always pays to have multiple antennas and a way to switch between them quickly.
     

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