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questions: long line antenna

Discussion in 'Home Brew' started by RustDemon, Nov 10, 2011.

  1. RustDemon

    RustDemon Active Member

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    been doing a bit of reading and I was considering the various antenna types as well as their ease to DIY, and figured the long line would probably be the easiest place to start. Like any7 project IME its a good idea to get some experienced help BEFORE starting. so here are a few questions.

    1: is thicker wire better than thinner wire for receive and broadcast? min guage?
    2: what is the minimum length I should consider?
    3: is aluminum better than copper wire or vice versa?
    4:would doubling the wire help or hurt AKA a U turn at the end all the way back to point of origin?
    5: can I make my long line in a L shape horizontally to eliminate the semi-directional nature?



    I think thats about it for now.
     

  2. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    RD, how about details 4ur your idea?
     
  3. RustDemon

    RustDemon Active Member

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    basicly. I am going to run a wire from the peak of my roof over to the peak of my garage both are solid so a simple spring and insulator at each end can compensate for heating cooling contaraction and expansion. then down in the window to my device I have all kinds of different wires I can use from 8 gauge copper to 14 as well as some 10 gauge aluminum. all of them are insulated. one hook on the garage one hook on the peak of the house. it will run from 12 feet to about 35 feet. higher if I put a mast up and attach it to the top of the mast.

    I also considered just running a long wire around the circufrence of my roofline, cornering off near the power lines come in so as not to get too close.

    the theory seems simple just use one long wire.

    running it in the path I have picked will give me an southeast northeast broadcast rx pattern.
     
  4. Black_Bart

    Black_Bart Member

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    a thicker wire will be more broadbanded.

    a thin wire will tune to a narrower piece of radio spectrum.
     
  5. Moleculo

    Moleculo Administrator
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    How long is the wire run you're considering? What bands are planning on using?
     
  6. Beetle

    Beetle Sr. Member

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    I don't know where you've been studying about Long Wire antennas, but they're pretty effective when installed properly. Their radiation pattern has lots of lobes, which will change direction and number as frequency is changed (or antenna length is changed). Feedpoint impedance will vary over a wide range, so a very good matching network is a must.
     
  7. W5LZ

    W5LZ Crotchety Old Bastard

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    First, give this some thought. Most 'end-fed' antennas require a ground system to work well. That ground system is basically the 'other half' of the antenna, and the better that ground system the better the possible performance of the antenna.

    1: is thicker wire better than thinner wire for receive and broadcast? min guage?
    The wire should be large enough to hold up it's own weight and then a little bit more just for general prevention of it falling down. After that, the 'size' of the wire makes no appreciable difference.

    2: what is the minimum length I should consider?
    The length is one of those things that varies quite a bit. A general 'rule of thumb' is a quarter wave length at whatever the lowest frequency of use will be. Longer is better till you run out of room to hang the thing, or wire, whichever comes first?

    3: is aluminum better than copper wire or vice versa?
    There are differences in the 'conductance' of different metals. Those differences make no differences at HF radio frequencies. Use whatever you happen to have the most of, or can find for a reasonable price. If that wire happens to be insulated, it'll work just fine. Same for bare wire. It just doesn't matter. One thing about that is that aluminum is kind'a hard to solder to, so up to you.
    4:would doubling the wire help or hurt AKA a U turn at the end all the way back to point of origin?
    Maybe, but not really. 'Folding' wire, making a 'folded' antenna, does affect the impedance of that antenna. Using twice the amount of wire in such a folded antenna doesn't increase the amount of signal radiated or received. It also depends on how much distance is between the folded conductor. Small distance is the equivalent of a single wire. A large distance makes the thing into a sort of 'loop'ish thing which can change it's radiation characteristics. That can be either good or bad, depends on the particular shape and what your purpose is.

    5: can I make my long line in a L shape horizontally to eliminate the semi-directional nature?
    That's a good question, and I won't predict it helping or not. It'll be sort of directional no matter what you do unless you stick it straight up. The reason most people use an 'L' antenna is lack of room to make it straight. But they do work, so if you want to try it, do so. But try it another way too so you'll have something to comparir it to.
    Have fun.
    - 'Doc

    One last thing. The impedance of a 'long wire' antenna can be almost anything, so a way of matching that impedance is a very good idea. A tuner is one way of doing that.
     
  8. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    What Beetle and doc,W5LZ, have said sums it up pretty well. I used to have a 600 foot longwire antenna and it worked great in the line of orientation which was to the north-west. On 20m it had about 8 or 9 dB gain theoretically and worked very well into Japan.

    Just a note about longwire antennas versus long wire antennas. Did you catch the difference there? Note in one case it is one word and in the other case it is two words. That subtle difference makes all the difference in the world in what type of antenna you are talking about. A long wire antenna is simply a wire antenna that is relatively long. It can be any length as long as it is lengthy. A longwire antenna by definition must be at least one full wavelength long at the lowest frequency of operation and is often several wavelengths long on the higher frequencies. My longwire antenna was about ten wavelengths long on 20m and over 20 wavelengths on 10m. Most people erroneously call any long piece of wire a longwire antenna.
     
  9. RustDemon

    RustDemon Active Member

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    ok that helps a lot guys.

    first I want to clarify, I have been doing a lot of reading studying on HAM which has a million subjects and have just barely scratched the surface of a lot of them. I havent "studied long wire antennas" persay, more like glanced at them. and looked at a couple designs. I figured it would be one of the easiest to build and went from there to here to ask about them. I came with no more than a vague idea on the subject.

    so What I am gathering is:

    12 gauge insulated wire should be fine.

    the relative height of my buildings and the fact I am completely surrounded by powerlines makes it almost pointless to build one running from the roof of one of my buildings to the next, I seem to be too low using this method. I'm going to have to take a close look at the trees in my area.

    since I was planning on using it at 10-12 meters a 100 foot piece would work for 10 but not 12

    a u turn is pointless.

    More questions:

    Does a Long Wire have to be horizontal or can I run it vertical?

    how on earth would I tune it?
     
  10. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    N4UJW ANTENNA DESIGN LAB - Ham Radio Antennas - Design 0r Build Your own Ham Radio Antenna

    Some more reading for your pleasure.

    A lot of questions in your post.

    Most non resonant antennas are either using a matching device at the feed point or a tuner in the shack. Since you want to multi band this antenna a antenna coupler ( antenna tuner) would be recommended and ladder line to feed the antenna.

    the bands you are wanting to work can be worked using an IMAX2000, no tuner required as it has a good VSWR input on those bands.

    The more vertical your antenna is the more vertical properties it tends to have IE inverted L type of antenna.

    Or you could build a fan dipole for your needs, all type of options that will work, just depends on what you want to try and use.

    for DX limited space it is hard to beat a vertical for cheap down and easy.
     
  11. RatsoW8

    RatsoW8 Supporting Member, W9WDX ARC Member - WD8T

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    For a new ham going with a 10/12 meter antenna; start reading about dipole construction. Resonant dipoles are the very best antenna for a new ham to become familiar with and very easy to build and tune. Down the road, when you gain some experiance and antenna knowledge, you can venture into the world of longwire antennas.

    Start by building and tuning a resonant dipole for 10 meters first since you'll have 10 meter phone priveledges with a Technician license (when you are licensed).

    Just keep it simple to begin and youl'll learn more and be less frustrated.

    Good luck and 73'
     
  12. RustDemon

    RustDemon Active Member

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    That seems to be sound advice. the resonant dipole doesn't look much more complicated than the long wire.

    the antenna tuner is probably the hardest thing for me to come up with. I know they are relatively inexpensive but finding one local is going to be a PITA
     
  13. RustDemon

    RustDemon Active Member

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    so, for a 1/2 wave length dipole I need 196 inches of wire split in the middle, sperated by an insulator each half of the wire connected seperately to the inner and outer conductors of a piece of coax. prefferably a full wavelength off the ground which I think I can get if I run an inverted v. and use my roof line with stand offs at the peak and eaves to form the v.

    should my wire be solid or can I use braided wire?
     
  14. W5LZ

    W5LZ Crotchety Old Bastard

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    Some advice about tuners.
    First, think large, or maybe very large. Not the power handling ability so much, but in size. That's because the size of the coil and capacitors determine the tuner's abilities. And that's because there are some very large voltages which can be present and the need for separation between the plates of those capacitors and coil windings to keep from arcing. Those voltages are normal for impedance transformations.
    New tuners are very nice to have. But, there are quite a few of the older tuners that will do just fine, if/when you can find them. They may not look very nice, but it they work, who cares? Auto-tuners are also nice. But just how hard is it to learn to twiddle a few knobs? The biggest 'trick' with manual tuners is writing down the settings for a particular band/frequency! Saves a lot of twiddling if you can go 'back' to a previous setting, you know? The more preparation you do the easier it is. Take some time and find those 'sweet spots' before you really need to.
    - 'Doc

    finding things locally isn't the easiest thing to do with a lot of things. So, order one. Just know (or have a good idea what you think you want) what you want before doing so.
     
  15. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    468/freq is the formula for any half wave dipole
    234/freq will give you a quarter wl.

    It is possible to make a 10/11/12 meter fan dipole, one coax feeding it and three bands.

    I do not know how it will work with the frequencies being so close to each other.

    Solid or braided wire or whatever you have laying around will work, electric fence wire is cheap and works well. PITA to solder
     

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