End fed wire from attic to outdoors?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by AE4CH, Jun 11, 2021.

ad: L-HROutlet
ad: l-rl
ad: Left-2
ad: L-Geochron
ad: abrind-2
ad: Left-3
ad: HRDLLC-2
ad: L-MFJ
ad: MessiPaoloni-1
  1. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    Find another support, put the transformer or whatever at the soffit ventilation, and run the entire length of the antenna outside, to your 12 ft. point on the tree (unless there's some way to get it higher) and then to your second support. Bend the wire to fit if necessary. It is more important to have the high-current points on the antenna high and in the clear than it is to have them in a straight line.

    Having the high-current part of your antenna inside your attic, a few feet from your house wiring, is likely to cause interference to and from your set-up. You will be much happier with the antenna outside!

    As others have pointed out, you will want to address lightning grounding; in addition, if it were me, I would make provision to lower the antenna in foul weather and have as much of it as possible lying on the ground when lightning threatens.
    AK5B likes this.
  2. AK5B

    AK5B Ham Member QRZ Page

    I agree, and even though I am putting together a proper multi-coax and control line entry point at my service panel ground I am also suspending some of my antennas from trees so they can be lowered to ground when not in use. We get a lot of lightning storms here on the Gulf Coast and having a rope and pulley system in place is an idea worth implementing wherever possible (good for stealth reasons as well).

    Marine-grade pulleys are the only way to go when using pulleys and small ones for thin Dacron or Kevlar antenna ropes are not expensive.


    http://www.spiderbeam.us/product_info.php?info=p241_100m roll Kevlar guy line (1mm).html

    (Spiderbeam also sells a 2mm version but the 1mm is extremely stealthy)

    Also of possible interest:

    (use one of these on your AC service panel ground rod with one of these (or similar such as Morgan or Alpha Delta):


    Hope this helps!


    AE4CH likes this.
  3. G0KDT

    G0KDT Ham Member QRZ Page

    In this link it would appear that the idea is to use the coax as the counterpoise, hence keeping it from earth or from taping it to any metal pole/tower to support the coax.

    So what if you put a counterpoise of at least 0.05 of wavelength at lowest antenna frequency on the earth side of the transformer and put a common mode choke at or just before the transformer?
  4. WA7ARK

    WA7ARK Ham Member QRZ Page

    Yes, that works:
  5. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    Not quite what I was saying earlier in post #7. You ought to run the coax down the outside of the wall to the earth grounding point, NOT a ground wire. Then bring the coax inside at that point.

    Also, keep in mind when picking a location that whatever grounding you do for the antenna coax ground MUST be bonded to the AC service entrance ground. The optimal solution is if the coax entry and the AC entry can be at the same rod or close by, otherwise you must run a longer bonding wire to the AC entry.
    Last edited: Jun 11, 2021
    AK5B likes this.
  6. G0KDT

    G0KDT Ham Member QRZ Page

    OK, So next questions.

    1. Does the counterpoise need to be aligned diametrically opposite the primary antenna wire?

    2. IF you didn't use the counterpoise the coax radiates. Presumably as far down the feeder coax as the common mode choke. So that would have to be taken into account for ICNIRP EMF safety distance assessment. What distance is FCC suggesting at 100w, 100% tx cycle on 80m?
  7. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    AFAIK only Florida gets more thunderstorm activity than the Texas Gulf Coast.

    I don't lower my current set of antennas, BTW. I have the feedlines lying on the ground for a dozen feet or so before they go to the remote switch. Then, I disconnect the feedline that goes from the switch to the shack, at both ends. This could easily cost me the switch someday, but I think the lightning is less likely to jump sideways 50 ft. or so to strike the house itself when there will almost certainly already be an ionized path along where the feedlines used to be, with that path going to ground where the coax used to rest on it...

    I, like you, am in the process of building a proper entry point; I've learned a lot from reading these boards. But even after I've done that, I'll likely handle the coax the same way.

    (Speaking of thunderstorms, Jeff, I am in the process of starting to cut my grass after three weeks of the ground being too muddy to do it. Some of it is so tall that I have to scythe back about an eighth of an acre before I can pass the lawn mower through it. I'll bet you and/or some of your neighbors are in a similar state?)
    Last edited: Jun 11, 2021
    AK5B likes this.
  8. AK5B

    AK5B Ham Member QRZ Page

    Yes. The last rains were heavy and now it's partly cloudy/sunny and hot every day. Lawns and mosquitoes growing like crazy as I knew they would.

    This photo was taken a couple of weeks ago the very day after I had used my weed whacker to cut the grass all the way down to dirt (we don't favor lawns at all or any other type of luxury resort for mosquitoes, and plan to do a full rock garden to replace it when we can afford to):
    IMG_4768CC.jpg It was really coming down in buckets that afternoon---and now, maybe 1 1/2 or two weeks later it is ready for another down-to-dirt trim.

    But I was just about to go outside, fire up my angle grinder and cut a big piece of aluminum plate for my entry panel, coincidentally---I'll get to the lawn tomorrow or the next day when I recoup my energy. Working in the summer heat takes a lot out of this old guy!

    As for lowering my antennas, I figure it can't hurt and I actually don't put them all the way down on the ground. Those lightning strikes spread out and travel through the dirt/mud anyway. ;)

    I'll be finishing my grounded entry point sometime next month as I'm going on a long road trip soon and still have things like Polyphasers, Mix 31 toroids and a big copper ground clamp on order. Everything will be here by the time I return---and I'll post a thread in the General Technical Questions forum once it's all done.


    WB5YUZ likes this.
  9. AE4CH

    AE4CH Ham Member QRZ Page

    I discovered what may be an ideal position for the antenna feed point. What about an unused metal gas furnace tube vent with cap? I have an old gas furnace exhaust vent that is about four inches around. It is capped off inside the attic, and has a weatherproof "hat" on the outside. I can see that the EFHW or an OCF dipole could be placed at that point, and the coax run down the vent, across the attic, and down the wall to the office. I already have wires from the attic down into the office, at a phone / ethernet box. So, I could add a box for the antenna coax there, and easily fish from the office up to the attic in that wall space. From the unused furnace vent position, I have an ideal OCF mounting location, for inverted vee, with wire traversing the backyard towards the wooden fence line. Easily can add a 12-foot mast attached to the fence both places.
  10. KC3PBI

    KC3PBI Ham Member QRZ Page

    If I follow your description correctly, that still doesn't get you any safety from lightning strikes.

    If/when your antenna wire gets hit by lightning, it will probably vaporize (explode) with a loud bang.

    of the wire between the strike point and wherever it eventually gets to ground will vaporize. If I follow you correctly, the first grounding opportunity will be after the lightning has gone through the antenna wire, through the coax, through your radio, and its power supply to the ground pin on the outlet on your shack wall. So all of that stuff would go BANG as well.

    You want to offer lightning a way to jump off your antenna wire to your existing house ground before it enters your home, so that the potential damage done by that exploding wire is 100% outside where at worst it will singe your paint and scare the neighbor's dog.
    N0TZU and AK5B like this.

Share This Page

ad: MonitorSens-1