Making an elevated vertical antenna

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KB1CKT, Oct 24, 2020.

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  1. KB1CKT

    KB1CKT Ham Member QRZ Page

    I'm feeling a bit foolish in asking, but: how does one elevate a store-bought vertical? Do you buy a length of 2" OD pipe that is 10' long, dig a 4' deep hole and fill with concrete? I read all about how people elevate their antennas so as to get elevated radials, but I'm not sure how they do it--are they all using a tower section (along with typical tower install, base and all)?

    I have some tall trees but I've yet to snag a branch more than 40' up, and then the antenna winds up hugging the tree (in case I wanted to make a wire antenna). I was trying to get an antenna out in my woodlot but I gave up. I have a small open spot where I could do something, I think I can get away with radials sloping down and guys and whatnot, but I'm at a loss as to how to "get up there".

    o_O

    No end to articles about ground mount verticals... which I used to have and would be fine with (have a 6BTV that is itching to go back up).
     
  2. AK5B

    AK5B Ham Member QRZ Page

    I used an 8-foot 2X4 for my 4-band fan and a 7-foot T-post for my screwdriver with a half circle of radials; all you need is a few feet above ground in most cases. Additional height is always good but once you get above the ground clutter, stucco walls, metal fencing, etc, you're in a good spot. When I operate portable I use a 17/20meter fan Marconi with 2 radials per band and they are about4-6 feet above the seawall I set up my antenna on. Works FB every time.

    Where animals and people could come in contact with the radials keep them 7' or more to be safe. If you have any horses, elephants or giraffes on the property then higher is going to be the only way to go.:D

    Remember what I call the Rudy Severns Rule= Two to fourteen 0.15 to 0.40 lamda radials elevated 4 feet or more over average ground become the equivalent of 120 ground radials.

    73,

    Jeff
     
  3. KB1CKT

    KB1CKT Ham Member QRZ Page

    Well, the spot I'm looking at is away from people, but one can't stop the bears and tigers. Ok, I kid on the tigers but we do have wandering critters... I have some temptation to just find a 4 to 6' pipe and put it down 3'. 3' is a foot shy of frostline but... Get up just 2' and leave everything up 2'? Use driveway markers for the ends of the radials? All well marked, and well known to the fam to not mess with? Hustler 6BTV is 40-30-20-15-10, although I want to add 17m as it's been open lately (might as well do 12 too some day). I think I have 60' open space for 40m radials (which would be detuned badly that low).
     
    AK5B likes this.
  4. KH6AQ

    KH6AQ Ham Member QRZ Page

    The 40 meter band radials up 2' from ground will not detune much. I ran an EZNEC model of a 40 meter ground plane and lowering its base from 20' to 2' above ground lowered its resonant frequency by only 100 kHz. The tune up procedure for the 6BTV will compensate, making the vertical a bit longer or shorter as needed.

    For the elevated radials to be more effective the antenna should be RF-isolated from earth ground so that RF current does not return thru lossy ground and up the mast to the antenna "ground." So, mounted on a metal mast buried in the ground the 6BTV base should be insulated from that mast. This can be done with PVC pipe cut down the middle to form two clamshell halves. The small gap between the two PVC halves is not a problem. And, to fully RF-isolate the radials and feedline from earth ground the coaxial cable should have a common-choke near the feed point. For 40-10 meter isolation this can be done by winding 12 turns of RG-58 (or RG-8X) on an FT240-43 ferrite core. This is per G3TXQ's designs. That ferrite core can be found at Mouser, Ebay and even at Amazon.
     
    Last edited: Oct 24, 2020
    AK5B likes this.
  5. W9XMT

    W9XMT Ham Member QRZ Page

    The NEC4.2 analysis below of a 1/4WL Ground Plane with 4 x 1/4 WL horizontal radials all elevated 2 feet above 5 mS/m, DC 13 soil reports that the effects of adding a path from the common point of the radials to a buried ground rod are pretty much negligible.

    [​IMG]
     
  6. N7WR

    N7WR Premium Subscriber QRZ Page

    I have had great success mounting a vertical on a wooden pole which was cemented into the ground about 3 feet with the top of the pole where I mounted the vertical being 10 feed AGL. I used 4 sloping radials which sloped down to 8 ft above ground. I agree with others that elevating the vertical only 2 feet would not be worth the effort
     
  7. N5CM

    N5CM Ham Member QRZ Page

    I have an elevated 80m vertical/160m inverted-L "fan" antenna fed through a 1:1 choke. The base of my wires is supported 9 feet above ground level (AGL) on a 4x4 post. The 4x4 is a 12-foot post with 3 feet in the ground.

    The post and the wires, AWG #14 stranded THHN, survived Hurricanes Laura and Delta, which were around category 1 when they got up to our location. My elevated radials, AWG #18 stranded TFFN, were trashed by falling limbs and a few tree tops. I just got them back up.

    The 80m vertical, 66'4", is supported from a pine limb that I accessed with my slingshot. The 160m inverted-L is supported by lines over three trees. The 3 support lines terminate at a pulley up about 80 feet (+/-). The vertical portion of the inverted-L is about 68 feet.

    My radials start out at 9 feet AGL and vary in height along their length from 7 feet (due to sag) to about 15 feet. According to what I have read, elevated radials should be resonant. I (6'2") can walk under all of my radials. I ran support lines from tree trunks to keep the radials from sagging too much. Most of the seven 80m radials are straight runs. The eight 160m radials zig and zag a bit to avoid limbs and tree trunks, but there are no sharp angles in the runs.

    If you have trees in the right places, you can run lines from them to a pulley such that your vertical can be placed between the the trees and not hug the tree trunk.
     
    M0AGP likes this.
  8. W9CYS

    W9CYS Ham Member QRZ Page



    I used a 40m ¼ wave wire vertical with elevated radials and had very good results. I suspended from a high tree branch with 4 radials about 8’ high crammed into a small suburban lot. Fed it with window line into 4:1 balun and generally worked most anybody I heard. Good antenna! QST article from the early-mid 90s I recall. I love cheap and easy antennas!
     
    AK5B likes this.
  9. KB1CKT

    KB1CKT Ham Member QRZ Page

    Went out to the spot and it's all sand. I had a 4' pipe and that went down easy but with only 2 feet in the ground it had all the strength of a wet noodle. That won't work well with a 6BTV, even with the 80m resonator removed. Wife wasn't crazy about pouring concrete in that area as we might some day redo that area and put in a large shed. A 6' pipe starts getting pricey.

    Poked around and did find a convenient tree branch at least 45 feet up--after several tries I did get a rope over it. This spot looks like I have decent trees to tie radials off. So whatever I want to make for it I guess. I feel like 20m & up is what I'm after, more DX! although who can argue against 40m? Need to find some more trees that I can use, undergrowth is a bit dense (and I'm not sure any of the trees I have antennas in are actually mine! so no aggressive tree work allowed). So it looks like I might go that route instead, for now.
     
  10. KB1CKT

    KB1CKT Ham Member QRZ Page

    Found a Radiowavz 20m dipole in the junk pile. Pulled that up on the branch. Now I see why people say that bringing feedline off a vertical dipole is hard--I had been hoping for the best, maybe get a fan dipole out of this, but that's a bit of work to pull off, no pun intended.

    Also learned that you should try to get ropes over live branches and not dead ones. Also one should not stand under a tree while pulling the antenna up. Thankfully the rest of what I snagged is alive and ready for the next antenna attempt.
     
    AK5B likes this.

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