Vertical installation with a few quirks

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by M0AGP, Dec 5, 2020.

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  1. M0AGP

    M0AGP Ham Member QRZ Page

    I am about to install a 6BTV at the bottom of my back yard in an area with trees (not deeply forested), and I thought to sense check my approach with the vast experience of the ham community.

    One constraint I have is that I want it to be pretty much invisible to my neighbors on either side (nobody is behind us) and I have found just the right spot: an oak tree around 60 feet high blocks it perfectly from the neighbor of main concern. It is about 9 feet from that oak tree and about the same distance from another of similar size. A third oak is a bit farther away, forming a triangle with the vertical inside the triangle. I also plan to paint it with camouflage colors.

    The clay soil is very hard, so I will pick up a post hold digger and just put in however many hours are necessary to get down 4 feet. I'll pick up a reciprocating saw to get through any roots down there, and a digging bar to pry rocks loose.

    Then I will have my beautiful assistant (the XYL) hold the 5-6 foot steel pipe in place while I pour in the concrete. I am a complete beginner with concrete, but there is a type called Post Crete that is pretty convenient: you fill the hole 1/3 with water and keep dumping bags of the dry mixture in until there is powder sitting on top. It sets in 10 minutes so I will need to have the magnetic level ready. It is apparently based on Portland cement.

    The radial situation is an unusual one: in this part of the back yard (where little would grow beneath the oaks) I had put down fairly thick black plastic and bark chips on top. My plan here is to sweep the bark chips away temporarily, hose down and dry off the plastic, lay 30 16 foot radials down (maybe #18 gauge stranded insulated wire) and first use lawn staples to hold them down, but also use black duct tape at frequent intervals, which should stick to the black plastic. I don't want little loops popping up that could create a trip hazard.

    I may pick up the nice DX Engineering radial plate, SO-239 thing and tilt-over mechanism as well.

    Once the antenna is installed, I use a RigExpert to get it resonant where I want it.

    Then I do a run of coax to the shack without burying it, drill through a cinder block and brick wall about a foot thick at an angle sloping downwards to the outdoors, push the coax through the hole and check that all is well from the shack end (about 200 feet of Messi and Paoloni later).

    Then I go back to the vertical, cut a long slit in the plastic directed towards the house, bury the (direct bury) coax in it, duct tape the slit shut, dig a slit/trench in the grass a couple inches deep, push the coax down and stomp the slit closed. The final run will actually be buried under gravel for about 30 feet or so, using lawn staples to keep the coax from popping up. Also some large heavy plant pots will be holding the coax down in this section.

    I will need to do something about lightning protection (I will read and learn).

    Ground rod near the shack entrance: right near this point is where the gas mains and the electrical mains enter the house. Not knowing the exact locations of pipes and cables makes me think slamming a ground rod down there would not be smart! I could easily connect some thick copper cable to the ground at the electrical junction box - not sure this is better than no ground rod though..? I could drill through an interior brick wall and connect thick copper cable/braid to the cold water mains... (I am in learning model here too). Not sure what is best here.

    The final stage is guying the 6BTV. We tend to have a season where we get gusts up to 70 mph once per year, so guying seems sensible. Given the vertical is in the middle of three 60 foot oak trees, I thought to use some dacron rope to guy them directly to the trees at a height of about 7 feet (avoids a trip hazard).

    I am ASS-uming that at a height of 7 feet, a 60 foot oak tree doesn't move around a lot, even in 70 mph winds. I wonder if there is data on this? (Maybe one of the cords should be a thick bungee cord for flexibility?) And I thought to attach the guys to the 6BTV somewhere around half way up.

    One thing to note: in the UK an antenna installation is considered a "building" and needs full planning permission! This is the reason for going the "hidden vertical" route...

    OK people - I am all ears! What am I about to do wrong, and what can I do that's smarter?
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    • Be sure if you use the tilt-plate mount that it's installed in such a way that you actually have the space to tilt the antenna over without it crashing into a tree.
    • If it were me, I'd attach the rope guys down lower on the trees and use highly visible little flags hanging from them from about 7' above ground down to where they're tied off so prevent walking into them.
    • I've never used concrete that cures in ten minutes, that sounds a bit "out there." Normal Portland mix takes a few days to set up and about a month to cure very hard. We do have "Quickrete" type stuff here that's popular for small loads like mailbox posts and such which is claimed to cure in about an hour, and I've used that for HF vertical tube mounts but always wait a few days, not an hour. To use that, the directions state to mix it with water (like in a wheelbarrow or such) outside the excavation and pour the mix in.
    • Using that, I'd never rely on a helper to hold the tube vertical; I use small rocks, stones, wooden shims or things that are solid and can't move once placed to wedge all around the tubing until it's vertical per a good level and then just pour -- it won't move.
    • If your cable entry point is close to your electric power utility entrance and service panel, I'd use "their" ground and just connect to it with a thick wire. IMO, this ground connection should be "outside," and a good bond to the utility ground. A separate earth ground probably wouldn't accomplish anything.
    • As added insurance if you get lightning, you might want to add a coax disconnect point outside the house so if you want to, you can just unplug the coax (outside) altogether in advance of a storm, or if you won't be home and using the antenna. This is pretty cheap and easy.
    • If you're going to paint the antenna, assemble and "tune" it first, so the clamps all secure the tubing sections clean aluminum-to-aluminum prior to any painting. Once set up and tuned, then I'd paint it.
    I doubt the oak trees will have much impact on the antenna performance; but even if they do, it sounds like that's the chosen option, so go with it!
    M0AGP likes this.
  3. KH6AQ

    KH6AQ Ham Member QRZ Page

    The 6BTV will benefit from guying and/or strengthing. Its weak point is the bottom 1.250" tube. A 1.235" x 0.062" wall aluminum tubing can be slipped over it.

    Guying halfway up will work well.

    The 4' hole is deeper than needed, especially in hard clay. I believe 18" will do just fine. No concrete needed, but it doesn't hurt anything but your wallet and your back.

    Nine feet is far enough from the trees that the 6BTV will not be detuned.

    I would use the DX Engineering tune up procedure.

    30 x 16' radials will be excellent. I use DX Engineering plastic lawn staples for lawn installations.

    The radial plate is great and I have used a cheap Ebay version. I replaced the zinc coated hardware with all stainless steel. The U-bolts can be used instead to attach radial wires.

    Yes, watch out for gas pipes! I hit a gas pipe going under my yard and to the neighbor. The gas company fixed it that day for $70 U.S.D.
    WB5YUZ and M0AGP like this.
  4. AK5B

    AK5B Ham Member QRZ Page

    Although the electrical safety codes are different than the US NEC reading the grounding stickies in this forum will enlighten you further. You should determine the location of your mains and other utilities coming into the house before you install the ground rod(s). One at the antenna will also be a good idea.

    You might want to rig up weighted guy lines with pulleys or screw eyes anchored in the big oaks just in case they sway in high winds.

    With those big trees for cover why not elevating the BTV and using fewer radials (also about 7 feet above ground will do well).

    Those are the first things off the top of my head.

    Good luck and 73,

    M0AGP likes this.
  5. WA7ARK

    WA7ARK Ham Member QRZ Page

    When pouring concrete around an in-ground short pipe that is intended to act as a "socket" for a tall, vertical pipe, I insert the tall pipe and temporarily rig some guy ropes to hold the tall pipe perfectly vertical while the concrete sets up... I just loosen/tighten the guy ropes to make the tall pipe vertical using a spirit level. The ropes can be removed after the concrete sets, leaving the in-ground "socket" true...
    K2CAJ, WA9FZB and M0AGP like this.
  6. KB1CKT

    KB1CKT Ham Member QRZ Page

    Not familiar with that kind of concrete, but if it was me, I wouldn't, only because I'm all thumbs and would find myself with cured cement and a lopsided pipe. Only if I got the pipe perfectly in place with bracing and then poured the stuff. Not sure about just dumping cement/quickcrete/whatever into a pool of water; maybe it will mix properly, as it might not be similar to the quickcrete I've used.

    Three trees around it? I'm guessing any 70mph wind will be well reduced before it gets to the antenna level. I'm not sure if it needs to be guyed if the 80m resonator is removed, as that is a big wind catcher. Anyhow. I wouldn't think the trees would move that much at the 7' level, and I suspect bungie or shock cord is not going to last over time. Maybe tie off but leave some slack, and see how it fares with time. [FWIW my 6BTV was well shielded and survived 10 years with no guying. YMMV.]

    My only reservation in all of this is the what-if the local authorities catch wind of this, if a permit is actually required. Yes, your approach is exactly how I'd go about it, and to hope for the best, but if it was $500 fine for not taking out a $50 permit...

    Lastly, if the trees are tall, you can (at a later date) toss a wire up into the trees and get more bands, by attaching to the base of the 6BTV, and using the tree to hold the wire up. Ahead of where you are right now, but you can add more bands later on.
    M0AGP likes this.
  7. M0AGP

    M0AGP Ham Member QRZ Page

    Just a quick comment on the planning permission - there is no attempt to save money on a permit - the way it works is that if you don’t apply for planning permission, nothing may happen. If they complain but are unable to see the antenna, sense would hopefully prevail. If you proactively make an application, all of your neighbors delight in their new found power to stop you from doing something you want to do, even if they are fully unable to even see the antenna...
    AK5B and W0GSQ like this.
  8. KB1CKT

    KB1CKT Ham Member QRZ Page

    Makes sense to me; I've heard of that sort of thing. As long as repercussions aren't a problem... what no one knows about will hurt no-one. Good luck!
    M0AGP likes this.
  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Aren't such laws wonderful?:)

    I love Los Angeles, where you don't even need any kind of permit to erect an antenna tower on private property (up to 45' tall, anyway -- above that, a permit is required).

    I've never seen any fall down.:p
  10. M0AGP

    M0AGP Ham Member QRZ Page

    I lived in So Cal in my university days - moving to the UK I kept thinking something was missing from the skyline...

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