My thoughts on MF and LF.

Discussion in 'The Low Bands - 630/2200 Meters - VLF' started by WA4ILH, Nov 9, 2017.

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  1. AA5BK

    AA5BK Platinum Subscriber Platinum Subscriber QRZ Page


    "a "football" and a floating wire. " I recently saw one of these for sale somewhere. Its odd to find this post. A synchronicity...
     
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  2. WA4ILH

    WA4ILH Subscriber QRZ Page

    I was never “ship’s company” on a sub but, as an E.T. stationed at SUBASE Pearl in the 80s, I helped (support) on the AN/BRA-16 VLF receiver system. It had a floating wire and a “whip.” I never saw the football but they also had a ELF system (now decommissioned) which may have had a football. I was talking to one of the Warrant Officers at SUBASE Pearl (who had a Master’s Degree in Electrical Engineering (MsEE?) about the ELF system and he claimed that ELF was not radio but simply “induction.”

    Tom WA4ILH
     
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  3. K1LKP

    K1LKP Platinum Subscriber Platinum Subscriber QRZ Page

    BRUCE,

    THIS PAGE HAS SOME GOOD SCOOP ON THE BUOY AND FLOATING WIRE.

    https://en.wikipedia.org/wiki/Communication_with_submarines

    73 ES MAY U ALWAYS BE BLESSED WID POSITIVE BUOYANCY.

    73 - K1LKP
     
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  4. AA5BK

    AA5BK Platinum Subscriber Platinum Subscriber QRZ Page

    Thanks! I see it but did not know what it was. Now I do lol and thanks so much!!
     
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  5. KC7JNJ

    KC7JNJ Ham Member QRZ Page

    East of me about an hour is miles of very old telephone wires still on the poles and glass insulators. Must be from around ww2 or before. (I know what your thinking) But I have followed the wires for miles, you can can see where the wires have been cut and left hanging down. They are all owned by the farmers now. I got permission from one of farmers to hook up to them. We did we could hear air port beacons from BC and Washington. But if any you get going on these bands I will have to see if I can hear you.
     
  6. W9XMT

    W9XMT Ham Member QRZ Page

    As maybe a data point on this topic, below is a rough analysis of an electrically short vertical monopole on 136 kHz when driven against a set of 24 x 10m-long radial wires buried in 5 mS/m, dc 13 Earth (average soil) — from a spreadsheet using equations found in antenna engineering textbooks.

    I added a blue rectangle around some rather eye-opening operating values that might be present in such antenna systems. The very narrow r-f bandwidth for an acceptable load match would be difficult to find and center on the operating frequency; also to maintain there once it was.

    [​IMG]
     
  7. DF2JP

    DF2JP Ham Member QRZ Page

    Hello friends of the really long waves ;o)

    But to ground conductivity you should note that the maps show only the natural conductivity of the region. But there are local factors that influence the conductivity.

    I lived in a valley surrounded by fields. These fields were diligently cultivated and fertilized accordingly. Every time it rained, this fertilizer washed into the swale at my place, which showed up in monster plants...12 ft tall nettles, brome thickets 2.5" in diameter. But the soil conductivity was tremendous. I didn't need any radials for my MF/LF antenna, just a 3m ground. I then buried additional radials (8x 400m) and compared the antenna current. Without radials the antenna current was 5,5 A with the 8 radials 5,8A, that was not worth the effort of digging.
    What I mean is, the map only shows the natural ground conductivity for a large area.... But locally it can look quite different.

    73 Joe
     
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