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Thread: 20M HOME MADE DIPOLE(no atu)

  1. #1
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    Default 20M HOME MADE DIPOLE(no atu)

    As i had no aerial at all for hf,I made a half wave dipole today for 20m from a design i saw on a website,hung it in an inverted v from the bedroom to the ground,trimmed it once with a pair of cutters.tuning around the band i heard a station calling from dublin ireland.Imagine my surprise when i replied and got back to him using only 5w of power from leicester uk! now thats qrp. 5 and 5 signals were reported. quite impressed with the aerial,swr is low(tested with fm)and I'm not using any antenna tuner at all,just the aerial straight into the back of the radio :mrgreen:

  2. #2
    Code Monkey 2e0sql's Avatar
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    Default Re: 20M HOME MADE DIPOLE(no atu)

    Well done, you cannot beat a cut dipole for a certain band unless you can put up a massive beam which most of us are unable to do :roll:
    Peter, 2E0SQL - http://www.2e0sql.co.uk

  3. #3
    Super Moderator 5B4AJB's Avatar
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    Default Re: 20M HOME MADE DIPOLE(no atu)

    Good job! - now you can make a super-deluxe ATU like this one...



    All components were gleaned from rallies for less than £5

    The only problem with this kind of tuner is you have to swap the antenna & radio coax connections around depending whether the load is high or low impedance. Oh, and that it's all live when transmitting - bazZing!

  4. #4
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    Default Re: 20M HOME MADE DIPOLE(no atu)

    nice construction job.I'm trying not to use one.I have a yeasu fc-30 i just purchased,and it's on it's way back to the shop for a refund(useless).won't tune unless the swr is already more or less ok.I though i may as well make an antenna that is resonant and do away with the tuner.I'm using the swr meter in the radio(yeasu ft897).I may cut a bit more away from the antenna.as it's tuned for about 14.000 to 14.150 and i really want it higher up in the band.

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    Administrator M0TZO's Avatar
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    Default Re: 20M HOME MADE DIPOLE(no atu)

    Quote Originally Posted by alvin 1230_0
    nice construction job.I'm trying not to use one.I have a yeasu fc-30 i just purchased,and it's on it's way back to the shop for a refund(useless).won't tune unless the swr is already more or less ok.I though i may as well make an antenna that is resonant and do away with the tuner.I'm using the swr meter in the radio(yeasu ft897).I may cut a bit more away from the antenna.as it's tuned for about 14.000 to 14.150 and i really want it higher up in the band.
    Get yourself the LDG AT-897 ATU. It's a much better ATU.

    LDG AT-897 on LDG website.

    I did and don't regret it. OK, it's a bit less well designed on the outside, but it's a much better unit on the inside where it counts.
    Paul, MØTZO - my websites
    Please PM me if you wish to change your username to your callsign

  6. #6
    Super Moderator 5B4AJB's Avatar
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    Default Re: 20M HOME MADE DIPOLE(no atu)

    Quote Originally Posted by alvin 1230_0
    I'm trying not to use...
    Well, you're on the right track, efficiency goes up logarithmically as you near resonance.

    An ATU will enable you to use it on other bands, with reduced efficiency, that's all...

  7. #7

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    Default Re: 20M HOME MADE DIPOLE(no atu)

    Quote Originally Posted by M0TZO
    Quote Originally Posted by alvin 1230_0
    nice construction job.I'm trying not to use one.I have a yeasu fc-30 i just purchased,and it's on it's way back to the shop for a refund(useless).won't tune unless the swr is already more or less ok.I though i may as well make an antenna that is resonant and do away with the tuner.I'm using the swr meter in the radio(yeasu ft897).I may cut a bit more away from the antenna.as it's tuned for about 14.000 to 14.150 and i really want it higher up in the band.
    Get yourself the LDG AT-897 ATU. It's a much better ATU.

    LDG AT-897 on LDG website.

    I did and don't regret it. OK, it's a bit less well designed on the outside, but it's a much better unit on the inside where it counts.
    I had a LDG auto tuner on my Icom 718. Now I liked how simple it was to tune a G5RV with that tuner.

    The problem I had was whenever it rained the tuner would not bring down the SWR to an acceptable level.

    Remember, the LDG tuners have memories. You tune an antenna on a dry day and the tuner remembers the settings.

    Now you try to operate on a day when it is raining and the tuner doesn't realize there is moisture on the antenna, or the feedline if you are running open wire feeders.

    However, the tuner remembers the original settings for 3.755 or whatever frequency you are on. But it doesn't know that antenna is wet!

    I sold mine, went back to using my little Dentron JR Monitor. Now I have a Dentron MT-2000A which is good for 2 KW. I have a trap dipole for 40/75 meters. I know where the resonate points are for each band. However I can also quickly tune that antenna on other frequencies I go to. I made a chart with the Transmitter, Inductance and Antenna settings marked down. So I can go from 3.668 which is the resonate point of the antenna to 3.755 and tune the swr down is less than 15 seconds.

    Nothing wrong with the auto tuners, but I think a good manual tuner can not be beat. JMO

  8. #8
    K7KBN's Avatar
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    Default Re: 20M HOME MADE DIPOLE(no atu)

    A properly-made coaxial-fed dipole for ANY band will work fine without the need for any tuner at all - as you have discovered. And in some cases, such an antenna will work well on more than one band: a 40 meter coax-fed dipole will generally work quite well on 15 meters.
    73
    Pat K7KBN
    Semper ubi sub ubi.

  9. #9

    Default Re: 20M HOME MADE DIPOLE(no atu)

    Keep in mind that a coaxial feed is extremely inefficient for feeding a non-resonant antenna via an atu. Where the antenna feedpoint impedance deviates greatly from the coaxial line impedance, the coaxial cable ceases to be coax any more, and becomes a lossy , partially grounded part of the antenna, giving you 'rf all over the shack' and a grotty signal. Open-wire balanced feedline is best for a random-length doublet (dipole) or loop, and is easily constructed. Each line should be roughly 3 inches apart. If getting open-wire line from the shack to the antenna is a problem, you can strap two equal lengths of coax side-by-side, the centre conductors going to each leg of the dipole one end, balanced output of atu at the other, the braids strapped together and earthed at the atu casing. This gives you 100 ohm screened feeder, which is several degrees of magnitude better than a single coaxial feed.

    As the original poster has found, a resonant antenna always performs well. An atu doesn't make a bad antenna good.

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