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14 foot vertical??

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KU7I, Jun 18, 2017.

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  1. KU7I

    KU7I Ham Member QRZ Page

    I have a 13 foot vertical up right now. It uses 39 feet of wire on a bamboo pole. It is a serpine winding so it goes up 13 feet, back down 13, and then up again 13 feet. I am feeding this via a 4:1 balun at the feedpoint to 300 ohm ladder line. It plays very well on 40 to 6 meters. Extensive ground system installed including multiple 8 foot ground rods throughout with over 60 radials 16 feet long.

    I am wondering if I would increase efficiency much on 40 and 30 by converting this to a 14 or 15 footer with a small 4 foot diameter 4 spoke top hat? I would possibly use the same serpine winding of 39 feet but with a 14, 15, or even 16 foot overall length so the last 1,2, or 3 feet would not be part of the winding, it would go straight up to the top hat. Top hat may only be a 3 or 4 foot t bar on top, say 2 feet either side.....or I could do the small 4 foot diameter 4 spoke top hat.

    Just looking for ideas. I dont know if it is worth the work to make changes. I enjoy the simplicity of this ant. No switching needed. All 39 feet is used on all bands but I am aware some parts of this are cancelled out due to phasing depending on the band.

    Again, looking to optimize 40 and 30 meters if possible by adding some overall vertical length with possibly a small T bar on top or simple 4 spoke top hat but not a big one.

    Comments please.

    Lane
    Ku7
     
  2. N0TZU

    N0TZU Premium Subscriber QRZ Page

    Let me see if I understand this. You have 39 feet of wire, it goes up the pole to the top, then back down to the bottom, then back to the top?

    If that's the case, then the only part of the antenna which is radiating anything of significance is the final 13 feet from bottom to top. This is because the current in the other two sections are in opposite directions and the fields from them mostly cancel out. You might as well have a single 13 foot wire.

    The radial field sounds very good, though a bit short. I assume it is limited by available space.
     
    KC8VWM likes this.
  3. NH7RO

    NH7RO Ham Member QRZ Page

    I am not sure about the rest of the antenna but I think adding a cap hat will always be a good idea to implement with any shortened vertical; it raises the current node away from lossy ground. Good on the extensive radial field, too but if you can elevate some a foot or two you might find a bit better performance as well.

    73, Jeff
     
  4. KC8VWM

    KC8VWM Subscriber QRZ Page

    C'mon Lane, you're pulling our leg right?
     
  5. NH7RO

    NH7RO Ham Member QRZ Page

    I don't he can reach that far---he's in southern New Mexico, Charles.
     
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  6. NH7RO

    NH7RO Ham Member QRZ Page

    I swear my computer ate a word ("think") when I posted that. Either that or I am getting senile.
     
    KC8VWM likes this.
  7. K9ZMD

    K9ZMD Subscriber QRZ Page

    I know I felt my leg tug about three times. Or maybe that was a reflexive urge to kick his young butt into a library to read an antenna book or two.

    On edit: Yes, I occasionally go into smart a55 mode, but usually I hit delete before submit. This time, it just felt good not to delete.

    Please please, could you tell us the source for this radical new antenna design? I don't care if it loads on all bands with 1:1 SWR, so will a dummy load. Not to say that your antenna won't radiate better than a dummy load . . . almost any untuned piece of metal can do that. In this case, a single 13 foot piece of vertical wire, once matched properly, will radiate as efficiently, or better, than your multiple winding lashup. So, strip off all those neato coils of wire except for 13 feet. Use the stripped-off wire to make a capacitive top hat or some radials.

    W8JI offers some wisdom at this site about problems associated with cramming a big antenna into a small space.
     
    Last edited: Jun 20, 2017
    NH7RO and KC8VWM like this.
  8. K6GB

    K6GB XML Subscriber QRZ Page

    I made a 1500 mile contact on JT65 with 5 watts on an oil-filled dummy load, wondered why my signal report was -26 :rolleyes:.
     

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