Wire antennas vs. windy environments

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KD0KZE, Feb 13, 2018.

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  1. KD0KZE

    KD0KZE Ham Member QRZ Page

    I've got a G5RV at about 29'. Being hung lower than optimal, in addition to poor band conditions lately, it has been hampering my DX'ing.

    It's hung over the house between an old oak (pretty solid, except for the large part that came crashing down last summer) and a large maple in the backyard. The upper branches in the maple are subject to major swaying in high winds. I wouldn't be surprised if the upper ones move 10-15' out of position, in any direction, in a severe thunderstorm. But if I can properly address this problem I should be able to reach a 40' height.

    What's a good way to hang a dipole and gracefully allow for major branch movements?

    I've devised a system in which the ends of the dipole pass through small sections of PVC pipe tied to continuous loops of dacron in each tree. I can raise/lower the antenna like a flag. One possibility is that I mount a tube on each tree and pass the antenna tie-off through it (not the dacron loop) and tie it to a weight, or a door spring. But I need about 10'+ of potential slack. So I almost need a spring-loaded spool caddy or some such. Any solutions out there?

    73, KD0KZE / Paul
     
  2. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    In warmer climates, we use pulleys and counterweights. Won't work so well where there is lots of snow and ice, though, and a lot of people in those areas will use bungee cords.

    However, a horizontal antenna at 29' should work pretty well on 20m.

    How are you handling the balanced line section? It can't hang straight down (which is probably optimal); there isn't room.
     
  3. KM4DYX

    KM4DYX XML Subscriber QRZ Page

    My dipole is supported by cord that goes over the tops of two trees and is then anchored on one end and counter-weighted on the other. The trees sway plenty but they sway under the cord, so to speak.
     
  4. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    Sorry. Poor writing.

    What I meant was, "It's best if it hangs straight down; but if the antenna is only 29' feet off the ground, there probably isn't room for that."
     
  5. N7WR

    N7WR Subscriber QRZ Page

    I have a few wire antennas here where the ends terminate near trees and then run through the trees with paracord. We get vicious winds. I use a medium tension spring at each end tied to the paracord and then tied (with paracord) to a t post in the ground. They have held up for years in winds up to 100 MPH
     
    KD0KZE likes this.
  6. KL7AJ

    KL7AJ Ham Member QRZ Page

    I don't know what I'd do without "550" cord. :)
     
  7. KD0KZE

    KD0KZE Ham Member QRZ Page

    The ladder line hangs nearly straight down, I'm lucky that the back of my house is near the mid-point of the G5RV. Unfortunately I have the slack in a couple loops (not good). We occasionally get wind gusts around 30-40 mph over the winter months, but it's much less than severe weather season in the summers. The other bonus is that there are no leaves in the trees over the winter months, so they don't sway much then. Only winter problem I've had was severe icing bringing the whole thing down one year. But most years it's too cold for ice here. Snow stays snow.

    If I can be safe against even 75 mph, I should be fine. The only times we go more than around that is if there's an F1+ in the area (which has happened), but at that point I'll have more things to worry about. A recent article in QST about trees has prompted me to get more serious about height. Having a few large/mature tree trunks within the radiation lobes, a couple loops in the ladder line, and 2-3 leaf canopies above can't be helping summer DX'ing. I'll take a look into springs first, since they're simplest. I want to tackle this in early April, once things start to thaw -- but before the leaves come back.

    I'm anxious to try my Chuckit! (tennis ball thrower) again. Last time I used it, I easily lobbed it right over the branch I wanted. Next time I'll try for pure altitude.

    73, KD0KZE / Paul
     
  8. K1TGX

    K1TGX Premium Subscriber QRZ Page

    One end of my dacron carrier for my dipoles is attached at the 60' level of my tower, through a pulley to the ground. There is ~ 30lbs of weight at ground level to allow for tree sway on the other end. The antenna is about 138' long and the most I have ever seen the weights go off the ground is about 6 feet. We get plenty of icing here (as recently as last week). This type of configuration I have used for decades and never had a failure (that may be because I usually end up changing antenna setups every 4-5 years).
     
    KD0KZE likes this.
  9. KW4EK

    KW4EK Premium Subscriber QRZ Page

    Another alternative to counterweighted lines is to use a series of pulleys and relatively long springs to tension your antenna. Depending upon how you setup the pulleys you can then spool out 1, 2, or 3 inches of rope for every inch of spring movement and if you use 1.5-2ft long springs then you can spool in and out quite a lot of rope. However, in an ice storm any system that depends upon moving parts may fail if the pulleys ice over early on, before the added weight of ice on the antenna brings it slowly down to ground level.

    As I live in upstate SC where ice storms are fairly common so I also engineer in an intentional weakness at the apex of my inverted V dipole antennaso such that it will simply break away and fall to the ground below if too much force is applied (whether from ice buildup or a toppling tree) so that the damage is controlled and mitigated to that which can be easily repaired -- though I also have a backup dipole antenna in my attic that can be quickly pressed into service.
     
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