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80m Vertical

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by AD5MD, Jun 6, 2018.

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  1. AD5MD

    AD5MD Ham Member QRZ Page

    I'm planning on installing a 33 ft vertical from Zero-Five and use it as part of an antenna to work 80m and I'm looking at 2 options to do it.

    1. Make an inverted L - Would anyone know more or less how long the wire should be from the tip of the vertical to another pole?

    2. Wind a wire coil on pvc form and attach to bottom of antenna. How many turns & what diameter form to use.

    Thank you

    Ernie, AD5MD
     
  2. K9STH

    K9STH Ham Member Volunteer Moderator QRZ Page

    About another 33-feet for the wire attached to the end or, better, about 66-feet of wire with one end attached at the base of the vertical spaced, with insulators at least 4-inches away from the vertical to the top of the vertical and then off to wherever. That would allow operation, without need for an antenna tuner, on 80-meters, 40-meters, and 15-meters.

    Base loading, with a coil, is very inefficient and should be avoided if possible.

    Glen, K9STH
     
    KU3X and NH7RO like this.
  3. AD5MD

    AD5MD Ham Member QRZ Page

    Glen,

    On your 2nd suggestion where you mentioned the 66 ft of wire, that's just the same thing as installing the wire on top of the 33 ft vertical...am I right? Or will there be a difference if I do it with the 33 wire attached to the tip? Also, do you think the antenna will still work efficiently on 40m?

    Ernie, AD5MD

     
  4. K8JD

    K8JD Ham Member QRZ Page

    If you just add another 33 ft wire to the top, you loose 40M but 80 would work fine. the total of 66 ft would have a VERY high Z at the feedpoint on 40M Hard to match
     
  5. NH7RO

    NH7RO Ham Member QRZ Page

    No, not at all. What Glen is suggesting equates to a "fan vertical" that will present a 50 ohm (+-) impedance on both 40 and 80 meters with one feedline. Switch bands and operate immediately with the same antenna!

    It's what I use for 10-15-17-20M here. Search "fan vertical guidance" to see my old thread for more info. If you can do this it will be better than a single inverted L for 80 which is what you'd have by attaching a wire to the top only.

    73,

    Jeff
     
  6. K9STH

    K9STH Ham Member Volunteer Moderator QRZ Page

    MD:

    Using a 66-foot wire, attached at the bottom / feed point of the 33-foot vertical places the wire in parallel with the vertical. The effect, on the resonant point of the 33-foot vertical, is minimal and you keep the ability to use the vertical on both 40-meters and 15-meters. If you attach 33-feet of wire to the top of the 33-foot vertical, then you effectively increase the length, of the vertical, to 66-feet and, as such, lose the easy ability to use the antenna on the 40-meter band and 15-meter band.

    Glen, K9STH
     
  7. AD5MD

    AD5MD Ham Member QRZ Page

    Makes sense, so if that's the case I won't need to buy the expensive vertical....just a vertical pole that will stand against the wind. Any suggestions guys? Thanks

    Ernie, AD5MD

     
  8. NH7RO

    NH7RO Ham Member QRZ Page

    All you need is something sturdy like a Jackite kite pole or better yet---a Spiderpole or MaxGainSystems fiberglass heavy-duty mast. about 33 feet tall---and a bunch of wire.

    I used THHN (insulated) soft-drawn solid copper from Home Depot leftover from my antenna farm days in KH6 for my high-band fan vertical and only separated the elements a few inches. Doesn't seem to be much, if any interaction and I could have placed things closer together in retrospect.

    Remember the "N6LF rule" for elevated verticals: 4 radials per band 0.15 to 0.40 lamda at least 48" above ground. More are better and so is higher (mine are at 8-6 feet) but longer is not (0.17 to 0.25 lamda is about optimum IIRC).

    It will be fun and relatively easy to build and you'll probably save a bundle of bucks in the process.

    Have fun, Ernie and let us know if you have other questions.

    73,

    Jeff
     

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