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The Not So Simple Dipole

Discussion in 'Amateur Radio News' started by M1MRB, Apr 25, 2021.

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  1. M1MRB

    M1MRB Ham Member QRZ Page

    ICQPodcast Episode 349 -

    In this episode, Martin (M1MRB) is joined by Chris Howard M0TCH, Dan Romanchik KB6NU and Edmund Spicer M0MNG to discuss the latest Amateur / Ham Radio news. Colin (M6BOY) rounds up the news in brief and in this episode we feature The not so simple Dipole

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    News stories include: -
    • Updated Radio Frequency Exposure Rules Become Effective on 3rd May 2021
    • New 122GHz DX Record
    • Amateur Radio has a New Census
    • Radio Amateur Helps Rescuers to Locate Lost Hiker
    • YOTA Summer Camp Croatia Postponed to 2022
    • GB5UTA Active in June for U3A Event
    • 60 Metres in New Zealand
    The ICQPodcast can be downloaded from http://www.icqpodcast.com

    upload_2021-4-25_20-22-4.png
     
  2. IU3EGK

    IU3EGK Ham Member QRZ Page

  3. W7EED

    W7EED Premium Subscriber QRZ Page

    Did I hear the speaker say that a folded dipole is one half of the length of a conventional λ/2 dipole? Oops ...
    --
    73,
    Jim W7EED
     
    CE3AV, W1YW, K2XT and 1 other person like this.
  4. KD5PUR

    KD5PUR Ham Member QRZ Page

    You did, the overall length is the same but since it folded it's shorter than it's full length.
     
  5. W7EED

    W7EED Premium Subscriber QRZ Page

    Actually a half wave folded dipole is the same length as a conventional dipole; λ/2. The impedance is higher but the length is the same. From the ARRL Handbook 2017:
    Folded Dipole.JPG
    --
    73,
    Jim W7EED
     
    WA5VGO, K4FMH, W1LJ and 1 other person like this.
  6. W1YW

    W1YW Ham Member QRZ Page

    Jim is correct.

    A folded dipole is 1 wavelength in perimeter (as he showed). It has a higher drive impedance and a wider bandwidth than a 1/2 wave dipole.
     
    W1LJ likes this.
  7. W1YW

    W1YW Ham Member QRZ Page

    If you closely bend back a 1/2 wavelength-length dipole to 1/4 wave, you will get phase cancellation and a funky impedance. IOW the performance goes kaput.
     
  8. KB9SIR

    KB9SIR Ham Member QRZ Page

    I inherited one of these of something similar and would like to know more about it. It is about 18" separation speed with pic spreaders. What con you tell me about it? It tunes on about every HF band. I'm old but young in ham experience.
    KB9SIR. John
     
  9. W1YW

    W1YW Ham Member QRZ Page

    That 'skinny loop' in the picture is a folded dipole, and has 1 wavelength perimeter. Its used because it has a moderate--not narrow--bandwidth.
     
  10. W1YW

    W1YW Ham Member QRZ Page

    Maybe this will help. The red arrows are the currents, which are in phase. The currents go to zero and then reverse phase , every 1/2 wave. That's why the arrows are in the same direction on top and bottom.

    [​IMG]
     
    NU4R likes this.

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