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Lightning Arrestor for Ladder Line Feed

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W6SO, Mar 12, 2010.

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  1. W6SO

    W6SO Guest

    Can anyone recommend a good lightning arrestor to use for ladder line feed line on an 80 through 10 meter wire antenna system? I have seen many lightning protection devices for use with coax, but cannot seem to find one for ladder line.

    I suppose I could just put a knife switch at the line's entrance to the shack, but I would like something that I can just leave in the line and not have to remember all the time.

    Any suggestions?

    Thanks,
     
  2. WB2WIK

    WB2WIK Premium Subscriber

  3. AC0OB

    AC0OB Ham Member

    SparkLightning Arrester

    It appears WIK and I hit "SEND" at the same time. I think his solution is better.

    I don't know how these would affect your impedance but what if you used two of these,

    http://www.dxengineering.com/Products.asp?ID=98&SecID=48&DeptID=19

    One in each line?

    Another route might be to use a spark gap: On one of the spreaders (maybe nearest the house), bring a wire from each line toward each other and space them say 1/8" apart with the ends in an "L" shape; then apply a lot of silicone sealer to keep out moisture.

    Phil - AC0OB
     
  4. KB1NXE

    KB1NXE Platinum Subscriber

    If you look at the Wireman product, and not to detract from it, it's nothing more than a couple of lawn mower spark plugs screwed to a plate with a cap covering the electrode end. If you borrow from this idea (unless it's patented) you should be able to make your own for about $10.00
     
  5. KC8VWM

    KC8VWM Ham Member

    Last edited: Mar 12, 2010
  6. WB2WIK

    WB2WIK Premium Subscriber

    Yep, that's what it is. Even if it were patented (I doubt it), you could copy it for your own use just fine. Patent protections don't cover private use.
     
  7. N4CR

    N4CR XML Subscriber

    Non resistor plugs are getting hard to find these days...
     
  8. KC8VWM

    KC8VWM Ham Member

  9. AL7N

    AL7N Ham Member

    Ladder Line lightning arrestor

    Simple spark gap from each feeder wire to a ground plate.

    Can be made a couple different ways:
    1. Two Non-resistor spark plugs screwed into a ground plate or bar.
    2. Stand off an insulator block on the ground bar and thread two studs through it. Make the ends of the studs pointed, run them very close to the
    grond bar (very small air gap). Attach the feeder wires to the other end of the studs with ring terminals or something similar.

    Mount the thing OUTSIDE the house and bond it well to the electrical
    service ground as well as connecting it to a driven ground rod with a short direct heavy solid wire.

    The close air gaps will ionize and dump static accumulations just fine.

    Also (hopefully) they will discharge larger potentials from nearby lightning strikes by offering a path of least resistance that will work instead
    of the surge following the feeder leads inside.

    If the main lightning strike hits your antenna directly, it won't make any difference.
     
  10. K3STX

    K3STX Ham Member

    I had a ladder-line fed dipole up for 5 years before it blew down. Never had a lightning arrestor, never had a problem. And we have LOTS of lightning. Also have coax-fed dipoles/verticals. No arrestors. No problems.

    paul
     
  11. AD7N

    AD7N Ham Member

    It is my understanding Lightning Arrestors only protect your equipment from near-by lightning strikes, not direct hits.

    A direct hit will vaporize the ladder line and any simple "lightning arrestors" you have in line with it. All that's left is a small stream of ionized plasma where the ladder line used to be. This stream of plasma acts as a conduit for the rest of the lightning to ground into your radios. Trying to protect your radios from a direct strike with a simple lightning arrestor is like relying on a sheet of bubble wrap around your car to be your only protection in a head-on freeway crash. :D

    Lightning arrestors do work very well in keeping stray voltage from nearby strikes from getting to your equipment. If a small, tiny fraction of nearby lightning strike finds your antenna, the arrestor will keep it at bay.
     
    Last edited: Mar 12, 2010
  12. AD7N

    AD7N Ham Member

    The easiest, cheapest solution to deal with direct lightning strikes is to have a way to physically disconnect the feedline and have a "pigtail" you can throw out in the grass. For me, I installed coaxial "bulkhead" through my wall. This allows me to easily unscrew the coax and throw it out into the yard when a lightning storm is nearby. For a twinlead, two wingnuts for a quick disconnect would do the job. Note, this doesn't ensure anything. It simply minimizes the chance that the direct strike will get to your radio. If you're really concerned, disconnect the radio and put it in a metal filing cabinet.

    It is interesting to learn how the pros deal with direct strikes, like to a cell tower or AM/FM broadcast antenna. Here is a good paper on the subject:

    http://awapps.commscope.com/search/docviewer.aspx?docid=7882
     
  13. K9KJM

    K9KJM Ham Member

    Please be aware that the actual "device" used, (Lightning arrestor, Switch, spark plug gap, Etc) Is close to the LEAST important part of any lightning protection system.

    MUCH more important is the proper grounding and bonding of all ground systems. (Decent grounding is LOTS more than just running a skinny wire out to a single ground rod)

    If you "disconnect" wires (A very dangerous practice when a storm is nearby)
    Be SURE to either properly ground those disconnected lines OR remove them far from the building! To simply leave a disconnected line laying about on the floor is about like leaving a stick of dynamite on the floor!

    I much prefer some type of grounding switch if you do not plan to operate while the storm is overhead, Or if you do plan to operate during storms like many of us do, I.C.E. (Industrial Communications Engineers) has good products at a reasonable price:

    http://www.iceradioproducts.com/impulse1.html#2


    For some tips on lightning protection on a budget:

    http://www.scribd.com/doc/14868226/lightning-protectiontaming-thors-thunderon-a-budget
     
  14. VK6ZGO

    VK6ZGO Ham Member

    Two thoughts;-

    Back in the earlier days of Radio,many thousands of outside antennas were

    used by the general public,without any thought of lightning protection.

    OK, these were Tube Receivers,& you could buy knife switches with built-in

    spark gaps & other such junk,but a farmer in the backblocks of Western

    Australia, (Or Kansas for that matter),was usually more concerned with

    getting as much wire in the air as he could,to receive Radio Broadcasts

    from,usually a fair distance away.

    Lightning protection was rarely thought about.

    Even Hams,who might well have had higher antenna structures,didn't worry

    that much.

    Obviously, Solid State equipment is more fragile,but lightning damage is

    relatively rare.


    Secondly,twin feeders normally feed an antenna which is at least nominally

    balanced to earth,so the possibility of doing something along the lines of a

    earth for lightning induced transients is there.

    A large Inductor from each leg to earth is a possibility.

    The problem would probably be getting enough reactance to not affect the

    wanted signal,& not have too much reactance & resistance to be a good

    earth.

    Of course,a folded dipole could in theory be earthed at its centre,without

    affecting the balance.


    Now,as I've disagreed with the general consensus,I'll put on my fireproof

    suit!:D


    73, VK6ZGO
     
    Last edited: Mar 16, 2010
  15. AJ8MH

    AJ8MH XML Subscriber

  16. K9STH

    K9STH Ham Member

    Even if the idea was patented, using spark plugs for "lightning protection" has been around since at least the late 1920s and since the "olde tyme" length of a patent was 14 years (now 20 years) the patent would have long expired.

    One thing that you can do to prevent the effects of static electricity "build up" is to put non inductive resistors to ground from each side of the feedline. Values between 47K and 100K are very common and the effect on the feedline cannot really be measured without some very accurate test equipment.

    Glen, K9STH
     
  17. NJ1T

    NJ1T Premium Subscriber

    I.C.E. Makes arrestors for open-wire/ladder line

    http://www.iceradioproducts.com/impulse1.html

    I have used their coaxial arrestors for some years now. Very well
    constructed.
    You might want to look into Their Open wire Arrestor.
    73
    NJ1T (The deaf DXer)
     
  18. W8JI

    W8JI Ham Member

    There are inherent design problems with ladder line lightning arrestors.

    Pay attention to what KJM posted. The lightning arrestor is one of the least important parts of the system!!!

    On bands where the doublet antenna reaches the highest impedance, ladder line voltage might be 2000 volts or more to ground at a kilowatt. At 100 watts plan on 650 volts or so.

    Any lightning gap that will pass that voltage OUT will pass that voltage in. That won't be much protection for a solid state rig or a tuner.


    Best idea with ladder line is clearly to disconnect if you can get a big enough gap and ground the line to a good panel ground. My choice would be a knife switch on a good entrance panel like coax would normally use, or to disconnect and throw it outside away from the house.

    I think anything else is mostly kidding yourself.

    73 Tom
     
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