600 ohm open wire (ladderline) construction

Discussion in 'General Technical Questions and Answers' started by VA3GRV, Oct 5, 2006.

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  1. K8JD

    K8JD Ham Member QRZ Page

    Looked at the homebrew ladderline & Eyeball calculating looks like higher Z than 600 ohms.
    Someone I contacted on the air the other night told me he had a "homebrew dipole" ..Made me wonder if he made his own wire and insulated it with strips of silk torn from his wife's discarded petticoats??? Braided his own shield for the coax??
     
  2. N0WVA

    N0WVA Ham Member QRZ Page

    Ive just been through all this ladder line construction stuff. I spaced #14 at 5" with lightweight water supply line, the stuff they use under the sink. Cuts easy and is light. I drilled a hole in each end, then used zip ties to tie the wire to it. Well, After about 75 foot of messing with it, I siad to heck with it and bought some high power 300 ohm ladder line from the wireman. Its sooo cheap, its really not worth the hassle of making the open wire stuff, unless you are overly concerned about operation in wet weather. Open wire will work fantastic when wet, window line will have quite a bit of loss.

    So I used 200 ft of 300 ohm ladder line, then used what I had built of the open wire line to make a nice 5" spaced folded dipole for 40. And man is it broad banded. I would also guess that it is a pretty good match for the feedline, the only weak link in the system would have to be the Dentron super tuner. From what I hear its not truly balanced like a Johnson Matchbox, but at any rate, the whole lashup beats the pants off a coax system.
     
  3. W8JI

    W8JI Ham Member QRZ Page

    Let me toss this into the mix.

    The BEST impedance for the line is actually lower than 600 ohms. As a matter of fact if you plan the line length and antenna length correctly the best feedline impedance is down around 300 ohms.

    If you don't plan anything then it makes very little difference what you use.

    In a world where we assume your tuner handles a very wide range of impedances, any feedline impedance between a few hundred and several hundred ohms would be OK. It doesn't make much sense to plan line impedance when nothing else is planned.

    I would not bet your feedline would have much less loss than window line. Really low loss open wire line has very low loss insulators and bare solid conductors that are pretty heavy gauge. You have PVC insulation right around the conductor, right where the electric field is highest.

    The real important thing is you are BUILDING the line. That is what matters. That is what is really important!

    73 Tom
     
  4. N9FE

    N9FE Ham Member QRZ Page

    very simple, about 30 dollars total
     
  5. AG3Y

    AG3Y Guest

    Shellack indeed ! ! ! Whoooh "Senior Moment" ! Sorry, of course I was thinking of more modern clear varnish !

    73, Jim
     
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