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Trench Feedlines

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KB3SQX, Sep 14, 2019.

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  1. KB3SQX

    KB3SQX Premium Subscriber QRZ Page

    Hello All,
    I recently achieved General class privileges. I am in planning phases to trench 2 feedlines to middle of the yard from the shack.

    Can I place both feedlines in same conduit? Can I run other wires in the same conduit, such as screwdriver controller wire?

    Or is it better to separate feedines individually in their own conduit and the controller wire in a separate one?

    I want to do it right from the get go. Antenna and feedlines answers were so simple in Tech privileges. Finding HF to be a whole new world. Have had only one antenna for a decade for 2m/440. 3 months into General privileges and currently running on a horizontal wire at 30 feet, I am already staring at 2 to 3 antennas for various bands. Not complaining and having a blast on the HF side. More antennas, more fun and options.

    Thanks in advance for the input.
  2. WA7ARK

    WA7ARK Ham Member QRZ Page

    I would say that it is ok to run the control wires in the same conduit as the coaxes. You may have to use some ferrite chokes to keep CM current from your screwdriver off the coax. Dirty little secret; Marconi verticals have a lot more CM current on their feedlines than most folks imagine.
    KB3SQX likes this.
  3. VA7UO

    VA7UO Ham Member QRZ Page

    Vivek, it would be okay, isolate the lines as best you can with an RF choke at the feed point of the antenna and some ferrites as stated. Good quality RG-213 or LMR which has double shielding, ultraflex 400 is a bear getting through conduit if you have more than one cable in there as the jacket is more rubbery.
    I did that with one of my satellite stations with two runs of LMR 600.

    Glenn, VA7UO
    KB3SQX likes this.
  4. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Coax keeps the signal inside and outside signals 'outside". There is no problem laying multiple coax together or with power and control cable. No special choking required.
    KB3SQX likes this.
  5. WA7F

    WA7F Premium Subscriber QRZ Page

    Bury bigger conduit than you think you will need. It fills up quicky and you will likely want to expand the antenna farm at a future date. At least 1.5” conduit but, 2” is even better if it doesn’t break the budget. The last time that I checked the 1.5” had the best price point. Also, when investing in coax it’s not that much more expensive to do it right. Personally, I would not bury anything lower quality than Times LMR-400.

    Depending on the climate the conduit will accumulate water from condensation. I’m installing conduit next week to a new tower site and there is a bit of a downhill slope. It will have a few drain holes on the downhill end.

    My tower site is 100’ from the house and I will use a bunch of used 1.5” PVC conduit from a temporary installation at at former QTH. I’m running four conduits; one for Coax to the tower, one for power and control to the tower. The third and forth are for future use as the antenna farm grows.

    The backhoe rental costs more than conduit and once buried I have no intention of disturbing that soil again.
    KB3SQX likes this.
  6. N7WR

    N7WR Premium Subscriber QRZ Page

    Having done this many times I agree with the suggestion that you go oversize on the conduit to allow for additional wire to be pulled through at some point in the future. To facilitate that also run one or more "pull lines" through the conduit on your initial build. That way you can pull additional wires through. At my last QTH I used 4 inch conduit through which, originally, there were 4 runs of coax, the rotator control cable, and the control cable for a remote switch. I included 2 runs of 550 paracord as pull lines for future expansion. Over the years I used one of those pull lines.

    The current QTH is a whole different story. The previous QTH was formerly farm ground and trenching was not difficult. At the present QTH we sit on volcanic soil with millions of lava rocks ranging from tiny to boulders weighing several tons not far below the surface. Trenching is nearly impossible. I have downsized the antenna farm substantially and my coax runs are not in conduit. I use buryable coax and it is just a few inches below the surface.
    KB3SQX and K9ASE like this.
  7. K8ERV

    K8ERV Ham Member QRZ Page

    Don't forget to include a double length pull cord for future wires.

    TOM K8ERV Montrose Colo
    N0TZU, AJ5J and KB3SQX like this.
  8. WA4SIX

    WA4SIX Ham Member QRZ Page

    I'll be doing this at a new QTH in Florida. Going with 3" PVC. Weatherhead on tower end. Lead wool will be stuffed into the weatherheads, to prevent rodents.
    5' or so from the tower, there will be a French drain pit 4' deep with crushed stone. I will have a T fitting there to drain. THe drain will be screened.
    This is due to large amounts of rain & humidity/condensation.

    2-RG8s, 1 1/2" hardline & 2-RG11s(Parallel feeders). I will also have a couple pull strings in there.

    KB3SQX likes this.
  9. KB3SQX

    KB3SQX Premium Subscriber QRZ Page

    Thank you Mike. Appreciate the input and helpful.

  10. KB3SQX

    KB3SQX Premium Subscriber QRZ Page

    Hi Glenn,
    I am using the LMR 400. Thank you for the advice and is very much appreciated.


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