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Open Wire Line

Discussion in 'Amplitude Modulation - AM Fans' started by W2NBC, Sep 8, 2017.

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  1. WD4IGX

    WD4IGX Premium Subscriber QRZ Page

    Eh, well, I'm not going to be heard far on the air on AM at this point with just an FT-990. Maybe in the right conditions. But I wager it would work fine for, say, a DX-100 and be indistinguishable on the air from "true" ladder line. If I were running QRO, at whatever that level might be considered (375 watts carrier for 1500 PEP legal limit now?) I might arc the stuff or something. But I don't plan to do that, not with this, and while I may well go with the "true ladder line" when I re-run to a higher apex I don't really expect any difference. Other than, of course, people not calling my feedline crappy. ;)
     
  2. K4KYV

    K4KYV Subscriber QRZ Page

    I'm not the only one; here's an excerpt from an e-mail I coincidentally received this morning, not related to this forum.

     
  3. K4KYV

    K4KYV Subscriber QRZ Page

    I don't think ham use had anything to do with it, since hams were likely an extremely small percentage of the people who purchased it. It was primarily sold as low-loss TV antenna lead-in, unless someone manufactured a heavier version specifically for hams. With the advent of cable TV and more TV stations coming on the air after the FCC-imposed "freeze" in the 1950s, fewer people were in fringe areas and didn't need the low-loss stuff, so demand finally trickled off to the point that they quit making it. It was far more of a hassle to install than regular 300-ohm TV ribbon.

    To me, open-wire line is any parallel-wire line separated by individual insulators, whether traditional "spreaders" or ceramic stand-offs on posts and cross-arms. My line running from shack to tower is a combination of both. I use posts, cross-arms and standoff insulators, with spreaders spaced at regular intervals in between to maintain proper spacing in wind, ice accumulation, etc.

    It wouldn't surprise me if bare open-wire line were against some local building codes. I vaguely recall reading somewhere that NEC mandates that bare antenna wire and transmission lines be a certain minimum height off the ground out of reach from people touching it, and they have very specific specications for feedlines exiting buildings. I have several copies of NEC over the years, but I'll have to look that up and none of mine are very recent. But I doubt the electrical inspector goes round checking very many ham radio antenna installations, and he would likely be totally baffled by many if not most. Typical stations with vintage homebrew equipment are undoubtedly full of electrical code violations, e.g. transmitters built in open racks, breadboard construction, unenclosed knife switches, easily accessible high voltage, no interlocks, etc.

    There is nothing magical about 600 ohms. For example, mine is 440 ohms, #8 at 2½ inch spacing and #10 at 2" spacing. 6" spacing wouldn't have been practical to run up through the interior of Rohn 25, plus I had a large box of 2" EFJ ceramic spreaders. Even at only 2" spacing and running 10:1 SWR or more, it would unlikely arc over with several kilowatts of fully modulated AM.
     
    WD4IGX likes this.
  4. WA3QGD

    WA3QGD Ham Member QRZ Page

    You are correct as to adherence to the over 600 volt restriction's a layman's guide is just outside up on a pole for all to behold,as to the arcing flashing component of any line insulated or not when one exceeds the dry air flashover point of your spacing only the magnitude and duration count,once breakdown occurs it either progressively degrades or becomes self diagnostic and falls back to the ground,just because your unaware of any flashover does not mean it's not occurring .evidence of degradation on my scd 40 gray spreaders at the 1/4 points on the line at 100 watt carrier level with the usual wet or algae growing on the surface have me replacing them about once a year.Meggering the line has revealed just how the elements all conspire to keep fire out of the wire.To the guy bemoaning the "Crappy window line" works fine for what it is in a windy place not so great,put some scrote behind it on a wet day with wind and sway big voice peaks and bloviation,going to show up the weak areas.Learned a few things i couldnt reconcile with some of the "Books" got to studying the military TM's saw some proven ideas that could be expanded upon,Would think one might want to hear weaker station's better and work them with less watts because it's more fun.So DON ever Megger your line? 73'es
     
  5. W1VT

    W1VT Ham Member QRZ Page

  6. WB5HAK

    WB5HAK Ham Member QRZ Page

    I found this link with a great pictorial discussion of building the OWL with 4" spacers of the type W1VT mentioned. VERY well done tutorial.
    http://www.w1aex.com/owl/owl.html

    Don, WB5HAK
     
    N2EY likes this.
  7. WD4IGX

    WD4IGX Premium Subscriber QRZ Page

    Maybe an environment thing (is he in a coastal area maybe?) or maybe just the fact I've never left the stuff up long enough to have it rust.

    Again, I never said it was great or even as good, just that it's worked ok in my experience.
     
  8. K4KYV

    K4KYV Subscriber QRZ Page

    YMMV. Sure beats coax feeding an 18' high dipole on 160 or 75m. The stuff probably works satisfactorily for most cases, but there are better options out there, as I was thinking when I was running the KW through fret-line.
     
  9. WD4IGX

    WD4IGX Premium Subscriber QRZ Page

    Yup. Right now I have the apex of my antenna as high above the deck as my step ladder allowed without using the top step which is never steady enough for my nerves. The bottom of the deck itself is about 15' off the ground and I reached over my head so that does put it about 20-25' - house is on a side hill. I well know that's not good, but it's better than NO antenna and I wanted to finally get the thing up. Works well enough on 80 and 40 for east coast to middle NA, and I've been heard in Spain well enough for a partial exchange on 40 and to know someone was calling on 80, which given summer noise levels and barefoot rig and a total of maybe three hours listening when I get a chance isn't that bad. It will be moved up soon. The deck needs a lot of refinishing, boards replaced and such, and when my friend does that he will bring a better ladder. I can add at least 10-15' to that. Still not ideal but it's what I get on this little 1/4 acre lot with a house on that. It'll do for now. I'll change to W7FG feedline at that time and report back, but any improvement would be more likely due to the change in height. I'm not knocking it, I'm sure it's better. But when you start out this low the extra height is "mo better." :)

    I also may add an amplifier in the semi-near future, and I'd love to get some boat anchors and get on AM "properly" and for higher power especially for continuous carrier I'm sure it's a far better choice.
     
  10. N1CZ

    N1CZ Ham Member QRZ Page

    My loop antenna w/ integral balanced line has been up for only 5 years with no issues. It took a lot of initial f@rtin' around to finally make it right. Most of that is fighting with & climbing trees. This is a loop antenna with about 270' +- 20' wire in the air. I use Google maps to measure and I never tried to include droop. It's only ham radio, but obviously I thought about it.

    I never paid attention to manufactured "balanced line". Obviously I was aware of the various versions, but just because I could ... I tried various spreader lengths just to find out. To be clear, this antenna is no sweet heart. It does benefit greatly with an autotuner between the balun & the xcvr which is only 6" == two 3" jumpers. Without the autotuner there are many high impedance spikes between 80M & 6M that makes working the wider bands to dramatic. With the autotuner, most spikes are contained. It is not usable below ~3.6MHz. There is a story behind that. (Contrary renter behind me that no longer lives there. Yaay!)

    You are not going to see this antenna written in detail in the near future. But, it might be adaptable to many locales. I only studied/modeled mine. Although there really isn't much detail that could help. The way I did it, was not cheap. I thought a wire antenna would be cheap. I did buy a balun good for a few kW. And, you are restricted to buying the next length of wire and rope needed for the antenna (500' each I think). Then there are numerous pulleys (sheaves) plus surplus antenna support poles. But, if you can find the space ...

    There are also the options of a drop at the opposite side of the feed for trying out different terminations. If only there were more hours in the day.

    Yes, I am an occasional AM-er. Yaay to the sound of the Voice of America, thinking about 50 years ago.
     

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