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Re: [loopantennas] Replicating the ALA330s

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  • Don
    Wrought iron is not a very good conductor, not to mention the rust. But a 10 4 x 1/2 thick iron loop would be very heavy to support and keep from blowing
    Message 1 of 3 , Mar 31, 2010
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      Wrought iron is not a very good conductor, not to mention the rust. But
      a 10' 4" x 1/2" thick iron loop would be very heavy to support and keep
      from blowing over. I would assume you already have this material laying
      around, but aluminum tube is a much better idea. I would use a wood
      dowel or PVC pipe for a stub mast then whatever below that, even if you
      don't use a rotator. Works for me. Just about any coax will work
      especially if there is an amp at the antenna. RG8 or LMR400 is probably
      overkill. Google Burhans loop amp for a start. Wellbrook has a patent so
      you probably won't find that.

      Don
      Upland, CA
      LFL1010



      On 31-Mar-10 12:10, inacit wrote:
      > Hello everyone,
      >
      > I would like replicate the welbrook ALA330s and have a few questions;
      >
      > - I'm thinking of using 1/2 inch solid wrought iron to build the 1
      > metre diameter loop instead coppper or aluminum, any downside to
      > this? hollow, solid?
      >
      > - Are there any schematics or photos for the electronics available
      > online? I found a few posts stating there were pictures posted in
      > this group but I have not been able to find them.
      >
      > - Mast material, should I use an non conductive/ferrous antenna mast
      > to hold the loop? does it matter?
      >
      > - RG8x coax ok or LMR400 for a 20 foot lead in?
      >
      > Thank You all for any advice you can provice..
      >
      > Cheers,
      > JM
      >
      >
      >
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    • Chris Harris
      poor conductivity, weight, rust, difficult to work, magnetic interaction ... From: loopantennas@yahoogroups.com [mailto:loopantennas@yahoogroups.com] On Behalf
      Message 2 of 3 , Mar 31, 2010
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        poor conductivity, weight, rust, difficult to work, magnetic interaction


        -----Original Message-----
        From: loopantennas@yahoogroups.com [mailto:loopantennas@yahoogroups.com]
        On Behalf Of inacit
        Sent: Thursday, 1 April 2010 7:10 a.m.
        To: loopantennas@yahoogroups.com
        Subject: [loopantennas] Replicating the ALA330s




        Hello everyone,

        I would like replicate the welbrook ALA330s and have a few questions;

        - I'm thinking of using 1/2 inch solid wrought iron to build the 1
        metre diameter loop instead coppper or aluminum, any downside to
        this? hollow, solid?

        - Are there any schematics or photos for the electronics available
        online? I found a few posts stating there were pictures posted in
        this group but I have not been able to find them.

        - Mast material, should I use an non conductive/ferrous antenna mast
        to hold the loop? does it matter?

        - RG8x coax ok or LMR400 for a 20 foot lead in?

        Thank You all for any advice you can provice..

        Cheers,
        JM







        [Non-text portions of this message have been removed]
      • gmcjetpilot
        First if this is to learn, great. If this is to save money, bad idea, cheaper to buy it. You will still need a rotor, controller, coaxial and mast to mount any
        Message 3 of 3 , Apr 1, 2010
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          First if this is to learn, great.
          If this is to save money, bad idea, cheaper to buy it.
          You will still need a rotor, controller, coaxial and mast to mount any directional loop....

          It is an active or amplified magnetic loop. There are many circuits on the web. The "trick" is they run the DC voltage down the coaxial with the signal.... that is not hard to do, but I am making my own and will have dedicated power to the active circuit at the base of the loop. I just run a phone-line sized two conductor cable next to and with the coaxial. You are running coax, what is two more small gauge wire cable. We are talking about very small current at low voltage.

          One trick Wellbrook does, is wide band, with no tuning! How they do that, I don't know. I think it's cool but can cause some issues the wellbrook is known for, and that is bleed from high powered MW (AM BCB stations) into the SW. They make some versions that attenuate MW altogether to concentrate on the upper band. I am making mine tunable. It is a simple controller that varies power to the active electronics at the base of the loop. It tunes a Vari-capacitor, varactor, a solid state version of an air-capacitor.

          The loop should be non-ferrite (not iron), copper best, aluminum good. What I am doing is using PVC and running some Litz wire inside it. Done and done, very small loss in bandwidth v copper pipe. Another cheap and good option is make a square loop out of copper water pipe. A loop does not have to be a hoop, although a hoop is cool looking. I would use a 1 meter dia Hoop-loop like wellbrook if I could find one. The best I found was an aluminum hula hoop, used by professional performers. They are about $60 bucks each. A plastic hula hoop with wire in it would be good for indoors, but I think they are too light duty. You can make a wood frame like hub and (8) spokes (octagon) and run a wire around it. This might be good for a BIG 2 meter loop. You get into big loops with copper water pipe it will get too big to handle. If you have room and no neighbors to complain, make it bigger.

          By the time you track down all the parts, buy them (with shipping since Radio Shack has nothing anymore and they charge silly prices for parts), it will cost you almost as much as if you bought the Wellbrook to start with. You know the wellbrook will work. If the goal is to save money forget it. If you want the challenge and willing to accept it will not be as good as the store bought, go for it.

          To out perform the Wellbrook you need a BIGGER loop.... and that can be done, but than it gets to be something you will mount from and near the ground in a back yard, preferably with out obstacles nearby. This large "sculpture" will be pretty obvious to look at. My home owner by-laws only allow a 1 meter antenna dish.... so a 1 meter loop will do the trick. I am sure they might still complain.

          Cheers

          RG-58 or LM195 is fine for SWL receiver antenna ... 50 ohms.


          --- In loopantennas@yahoogroups.com, "inacit" <inaciot@...> wrote:
          >
          > Hello everyone,
          >
          > I would like replicate the welbrook ALA330s and have a few questions;
          >
          > - I'm thinking of using 1/2 inch solid wrought iron to build the 1
          > metre diameter loop instead coppper or aluminum, any downside to
          > this? hollow, solid?
          >
          > - Are there any schematics or photos for the electronics available
          > online? I found a few posts stating there were pictures posted in
          > this group but I have not been able to find them.
          >
          > - Mast material, should I use an non conductive/ferrous antenna mast
          > to hold the loop? does it matter?
          >
          > - RG8x coax ok or LMR400 for a 20 foot lead in?
          >
          > Thank You all for any advice you can provice..
          >
          > Cheers,
          > JM
          >
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