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Advice for Wire Reciving SWL Antenna

Discussion in 'Amateur Radio Antennas' started by bludytiger, Nov 12, 2010.

  1. bludytiger

    bludytiger Member

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    I am planing on putting up an outdoor wire antenna, but I am a little undecided on what antenna I should make. Normally I would try experimenting with a few and choose the best, however I am running out of good weather and would like to get one up before snowfall.

    I am planing on using it for receive only on shortwave bands. I live out of town and have a fair amount of space to put one up. I don't have a tower yet and am planing on using trees. I have one really big tree that is taller then anything around that I can use. Most other trees are not taller then the house.

    At first I was going to put up a 100' long wire, but I would have to put it lower on my big tree in order to keep it horizontal to the ground. I thought however that maybe I should do an inverted V since I have one very high point but I don't know if they are better then long wire or not. I also noticed that there are multi-band long wire and multi-band inverted V. Do these really help over single wire?



    Building them isn't much of a problem for me since I enjoy building my own stuff. I currently have 100' of shielded 12 gauge wire, PVC conduit for insulators, and TV coax for feed line. The only materials I really can't change is my feed line since I don't have access to 60ohm coax right now. Will the outer layer of the coax diminish performance on a dipole? If that is the case, should I go with a single wire fed long wire?
     
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  2. office888

    office888 Active Member

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    Make a beverage antenna if you've got a lot of space.
     
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  3. bludytiger

    bludytiger Member

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    I never herd of a beverage antenna before but just looked it up. That is a really nice idea, however might be a bit bigger then I want to build at the moment. That and I don't know if my trees are up to supporting that amount of wire. That is possibly a good project for me in spring.
     
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  4. TonyV225

    TonyV225 Supporting Member

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    a simple 80 mmeter dipole would work you can save room and use it in an inverted V configuration. I use my for transmit and then at night use it on shortwave once and a while on AM 1100 for Coast To Coast Radio. It works just fine ;)
     
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  5. sp5it

    sp5it Master of puppets

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    Shortwave you mean BC or amateur bands?
    I would recommend a loop antenna, K9AY.
    Take a look at this site: Antenna Special -- on hard-core-dx.com
    it can give some ideas.
    Mike
     
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  6. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    As stated before it all depends what you are wanting to listen to.

    If it is going to be an all around BC and SW amateur bands then by all means run you a BIG dipole as long as you can get it on each side.

    If you want to go even further attach a small antenna coupler to the antenna in the shack and then turn your reciever on to whatever frequency you want to tune the antenna coupler for the strongest receive signal, you will get some good weak signal reception this way.

    Loop antennas work good, they have their drawbacks with nulls, as do dipoles if erected at a halfwave length in height, if you are targeting BC stations you will not have that problem.
     
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  7. TonyV225

    TonyV225 Supporting Member

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    So all in all it boils down to what you are going to do with this antenna once you know that then building or buying one should be the easy part.
     
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  8. bioman

    bioman Active Member

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    BIG di-pole if you have the room as stated a "coupler" or "trimmer" will work wonders.....

    if you dont have enough room to put up 250+ feet of wire a G5RV works SURPRISINGLY well for SWL
     
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  9. bludytiger

    bludytiger Member

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    I was planing on building this one as somewhat of a temporary antenna until i have some more money and more time to get the best I can for my area. I think I'm either going to do the long wire or an inverted V dipole since I have most the materials. I know the inverted V is supposed to be more omnidirectional then a normal 180 degree dipole, but what about long wire? Are long wire best in certain directions.

    I'm somewhat new to the hobby as I'm sure you can tell. My radio is a Realistic DX-160 so it does support a balanced antenna. It also has an antenna trimmer dial on it. Is this what you were talking about?
     
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  10. W5LZ

    W5LZ Crotchety Old Bastard

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    From what you've described, and all things considered, a simple random or long wire would be the simplest antenna under the circumstances. That tall tree makes for a very nice antenna support structure as well as those other trees.
    It doesn't have to be in any particular shape, and isn't going to make a huge difference if it's horizontal, vertical, or a combination of both. A good length is the longest one that's practical for you. So, how good is your throwing arm? Do you have something like a large wrench/spanner, rock, or whatever that you can tie a cord to and throw over those trees, then use that cord to pull a wire over them? Higher is usually better than lower. An antenna is too low when you have to duck to get under it, or have to step over it.
    Receivers re not as 'picky' about what kind of antenna you feed them with (don't have to worry about impedances so such like with transmitters), almost anything will work. As the length of the antenna increases, the frequencies it will 'hear' get lower.
    A random or long-wire antenna doe require a fairly good RF ground to work well. That can mean the electrical ground system for your house's wiring, metal water pipes, or wire on or slightly under ground. Depth isn't important, but it shouldn't cause you to trip over it if walking around it. A feed line is also unnecessary. If you can string that wire down, and directly to your receiver, the whole thing is then an antenna.
    If you should have lots of wire in the air and want to see what a shorter length would act like as an antenna, give it a pull and shorten it (if the 'other' end is tied off, untie it first). If attach a cord to the 'other' end you can always pull it back to the length it was to start with. You have an adjustable length antenna!
    There are precautions you should take with long antennas like this. They tend to pick up fairly strong static charges from high winds or nasty weather. Disconnecting the antenna in nasty weather, and dropping the end out of the window (or however you got the thing inside the house) is a wise thing to do. It can bite you, like shuffling your feet on carpet then 'sparking'/shocking someone someone by touching them (static discharge). If that static electricity get's strong enough it can damage electronic equipment.
    That 'trimmer' on the radio will typically handle various length/sizes of antennas. Shouldn't be very difficult to 'hear' the change it can make, go for the strongest resulting signal when adjusting it.
    Lots of possibilities as to size and shape with receiving antennas, longer ones are typically 'better' than shorter ones. Do whatever is most practical for you.
    Have fun.
    - 'Doc

    A couple of definitions:
    A 'random' wire antenna is usually one that's shorter than a full wave length for the frequency(s) of use.
    A 'long-wire' antenna is one that is at least two wave lengths in length at the frequency of use.
    That 'frequency of use' is commonly taken as the lowest frequency you will try to receive.
     
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  11. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    Many good suggestions.

    I gave up trying to throw a line over a tree years ago. Fishing poles and 20lb test line is cheap. Old lug nut or any thing the right weight tied on to the fishing string and cast that thing over the tree, then tie/tape your wire or rope to the fishing line and pull it up over the tree. Saves the arm and gets some practice on casting when you are on the lake fishing.:D
     
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  12. bludytiger

    bludytiger Member

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    In that case, I will probably continue with plan A and go with the long wire. Ill use the 100' length I have right now. So far for RF ground, I have been using what I have left of 1/2 copper pipe from making my Super-J. It is about 4 feet long and I have it pounded down into the ground, somewhat under a bush so it is out of the way. I don't want to use the antenna wire itself to connect to my receiver because the the distance from the tree to the receiver is a little long for that and I would probably loose at least half of my antenna.

    I will use the TV coax to feed the antenna since I just got a large amount of it still on spool unused from a salvage place near by. I know to attach the braid to ground. And I wont need a choke on this one since it's not a balanced antenna, correct?
     
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  13. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    Sounds like a good plan and should work. Half the fun is experimenting.

    The choke question? Been a topic of debate for a long time on receiving antennas. Some say it lowers the noise level and allows better copy of weak signals. Others say it doe snot help any at all.

    Try the antenna without a choke and then if you happen to run across one later on put it in the antenna system and compare it.

    Comparison of Beverage antenna,magnetic loop antenna,and phased vertical receiving antennas

    good link for different type of receiving antennas.

    Have fun
     
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  14. bludytiger

    bludytiger Member

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    Well from what I understood, a choke will only benefit on a tuned antenna. A long wire shouldn't be effected as much from the feed cable since the feed is from the center copper wire, and the shield is HF grounded. Having the shield HF grounded seems to me like the equivalent of having your radio itself shielded and grounded properly. It should keep all the noise out. I'm still new to this, but that seems like the situation to me, so long as the braid on the coax is good and thick.
     
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  15. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    Try it and find out. The antenna can be discussed and debated all day long but until you actually build it and try it you will never know.
     
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