Need some info on antennas

Discussion in 'Survival Communications' started by SB21, May 12, 2017.


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  1. SB21

    SB21 Monkey+++

    1st off, I have no experience on short wave radios. But I'm going to put up an antenna for one for an older fella at my local Legion post. This antenna is just a coated wire that extends about 100 feet one way from the the co-ax connection point, and about 50 feet the other way. The directions for this is not very detailed and informative. But it does state that it is not to be coming into contact with any metal, or at least that's my understanding from what the guy is telling me. The man is wanting me to stretch this thing from the ridge of his roof, we're I've previously mounted a metal piped tripod for an antenna , extending out to a tree in the front yard, and one in the back yard. He bought some para chord along with this antenna. I don't know if I'm supposed to stretch the para chord out and wrap the antenna around the chord or what .i wouldn't think para cord would last to awful long exposed to continuous weather .I was thinking of mounting a spring at each tree to attach the ends to, to maybe give a little flex in the wire in case of wind. My question here is , how do I attach this thing if it's not to have any contact with any metal ? Will the antenna still work if say one tree is only 80 feet away, and the other is only 40 feet away ? Do I just let the excess wire hang down, or roll it up ? I'm going to try and get by the guys house tomorrow , so if need be, I will try and get the model number and name of the antenna. Thanks for any help you can give me, I don't want to do a half assed job for the man.
     
  2. ghrit

    ghrit Bad company Administrator Founding Member

    It's an off center fed dipole. The feed point should be supported, and both ends (obviously) need support as well. It is desirable, but not critical, that the wire be straight when viewed from above, but some deviation can be tolerated. It would be nice if both ends were at the same elevation, but that isn't too critical either. What is critical is the entire wire be extended, you cannot coil it in the least. The ends of the wire should have insulators supplied, and if so it's an easy matter to put a paracord end on them and toss 'em up a tree. Tie them off loosely, because you'll be taking the ends up and down during the tuning process. There's more, uv cuss, but the directions should not be too messed up. If you have the brand and model, we might come up with more. First, for you, is relax. Antennas are very difficult to screw up, and are (usually) quite tolerant.
     
    Oltymer likes this.
  3. azrancher

    azrancher Monkey +++

    I agree with ghrit, if it's a pre-cut off center fed dipole, and it sounds like it is, then it must be extended to it's full length. If it can't be, he bought the wrong antenna.. if you can extend it fully, throw the para cord over a limb and weight it down, the best way is to attach a pulley at the proper height and feed the cord thru that with a weight on it to pull the ends tight as possible, a support for the feed point is nice but sometimes hard to do, pvc pipe works, but antennas in trees are not permanent so work with it until you get a good signal out, receiving is no problem at all with a long wire antenna.

    Rancher
     
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  4. ghrit

    ghrit Bad company Administrator Founding Member

    To add (this morning, last night's note was a bit incomplete): Using the distances between trees you've mentioned, it is possible to make the wire work if you let the excess length hang straight down. There are two problems, first being how to attach the wire to the 550 cord to keep the wire out of the branches. Second is that tuning will be seriously affected. It will still work, just not as well as might be wished.
     
  5. Oltymer

    Oltymer Monkey++

    If attaching to a tree trunk or large limb then a spring from the tree to the insulator is a good idea as the tree will be moving with the wind. I have used a screen door spring in the past, but have swapped over to using a strip cut from bicycle inner tube that is 3/4 - 1" in width.
     
    3M-TA3 likes this.
  6. SB21

    SB21 Monkey+++

    Thanks for the help, feel free to revise this if you like. I'll try and get the model info. I have a feeling the guy really doesn't know much about all this, he does have his license but very little experience in this end of it. I think he's just got recommendations to get the best reception for his radio, but they don't know his house is on a small lot and not to many options for mounting this thing. If there's a website that may have some sketches for possible mounting scenarios, it might help me in mounting this so he can get maximum output and reception. I'm one of them guys that look at the pictures in the directions. Maybe that's why I took up residential contracting, just look at the blueprint. Thanks again.
    Also, where could I buy the insulators ? What type of store might have them, Radio Shack ? If I can find one open around here.
     
  7. DKR

    DKR Raconteur of the first stripe

    [​IMG]
    Windom = off-center fed antenna. More than one way to hang 'em.

    [​IMG]

    Best of luck helping your buddy
     
    sec_monkey likes this.
  8. ghrit

    ghrit Bad company Administrator Founding Member

    If this wire was bought as a kit, it should have end insulators in the bag. If not, RS may have something like these.
    Ham Radio Outlet Search Results
    Ye locale Hardewarry shoppe might have something similar too.
     
    sec_monkey likes this.
  9. ghrit

    ghrit Bad company Administrator Founding Member

    More than you'll ever want to know about wire antennas, including OCF. Not much in the way of practical info, but --
    Wire Antennas

    If the wire came in a kit, there should be end insulators included (AND a BALUN, a must have thing, that.). If not, these are similar to what you'll be looking for -
    Ham Radio Outlet Search Results
    They come in all flavors, and yes, Radio Shack might have some. So also might your locale hardee-wary shoppe. Or, just make some loops of paracord and tie the wire on just like with insulators. (Leave loose-ish until trimming/tuning is complete!!)

    I've been looking for some hints and tips on how to let the too long wires droop to fit the lot, but so far to no luck out side of antenna manuals that aren't (that I know of) available on line.
     
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  10. Brokor

    Brokor Live Free or Cry Moderator Site Supporter+++ Founding Member

    Radio Shack, going out of business/closing sales may still be going on. Great time to stock up on...stuff.
     
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  11. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    If it is just for Receiving, then it really doesn't matter much if you bend it, direction of installation, or much else.... Just do NOT get it within a foot of anything that might be considered Grounded... Heck, I have stretched 500' of stranded House Wire thru a bunch of trees, and had it work, just fine... If it is for Transmitting, then the above information should be used during the installation.
     
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  12. SB21

    SB21 Monkey+++

    Thanks for all the info. I definetly know more now than when I first posted . It will be for transmitting as well. I'll be seeing him tomorrow and I'll talk with him and see if he has any info on the tuning process. And I'll probably be trying to install on Monday . Thanks again guys, great info from all of you.
     
  13. Homer Simpson

    Homer Simpson Monkey++

    I have made "insulators" from plexiglass before. 1/4" thick rectangles 5" long by 1.5"wide. I drilled 1/4" holes 1" in from each end. It worked for my 11 meter dipole. Could make some out of wood also. Paracord would work but I don't know how long it would last.
     
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  14. azrancher

    azrancher Monkey +++

    A common insulator that most of us have around the house is PVC pipe, cut off 6", drill holes in both ends, and instant insulator.

    Rancher
     
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  15. WastedDaze

    WastedDaze Monkey+

    Para cord is an insulator too.
    Like Bruce said, if it's just for receiving then it's not that critical.
    On my portable 40mtr dipole I just have loops tied in the ends of the wire. Then I use nylon cord tied to the loops to tie off on a tree or what ever is available. Doesn't have to be tight, a little droop won't be noticed on the air and actually helps in NVIS config.
     
  16. SB21

    SB21 Monkey+++

    Just an update. Thanks for all of y'all's help. I think I finally got the man transmitting . Had to go back a few times and reposition one of his other antennas that was causing some interference , and make a few adjustments to the Dipole , but he's happy so far. Thanks again guys.
     
    Idahoser likes this.
  17. Idahoser

    Idahoser Monkey+++ Founding Member

    I realize this is too late to help you, but for anybody following along, I found this to be a helpful discussion
    $4 SPECIAL
     
    Dont and ghrit like this.
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