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QRP 1:1 Balun for Dipoles: Which toroid should I use?

Discussion in 'QRP Corner' started by KK6WPX, Jul 5, 2018.

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  1. KK6WPX

    KK6WPX Ham Member QRZ Page

    I have a couple ft50-43 and ft82-43 cores lying around and I want to build a 1:1 balun for dipoles. Mainly 40m and 20m. Would any of these cores be enough?

    My idea is to be as lightweight as possible. I want to avoid the larger cores.
     
  2. N8AFT

    N8AFT Subscriber QRZ Page

    Balun is really not needed for a dipole. Straight coax to wires works fine just as it has since coax was invented.
    RG-174 is ultra light and small. Great for QRP work.
     
  3. US7IGN

    US7IGN Ham Member QRZ Page

  4. KU3X

    KU3X Ham Member QRZ Page

    Feed 6 or more turns through either core and you will have a perfect balun.
    It is always a good engineering practice to use a good current balun.

    Barry
     
    KK6WPX likes this.
  5. AF7XT

    AF7XT Ham Member QRZ Page

    Last edited: Jul 11, 2018
    N8AFT likes this.
  6. K8JD

    K8JD Ham Member QRZ Page

    BalUn For Your Dipole
    Adding a BalUn to a coax fed dipole is done, usually, only if there is a RFI-in-the-house problem. (or because Elmer told you it was a necessity :rolleyes:)
    I added the MFJ 1:1 BalUn center device, in my 160 and 80M dipoles just to see if it made any difference, It has a handy eye bolt on top to hoist and hang the center of the antenna up, and a female UHF connector on the bottom to connect your coax. That was the main attraction and the $24 price is why I got those items.
    ELectrically, NOTHING is any different now ! :eek:
    PS; I have been feeding dipoles with directly connected coax feedlines since 1960 and never had a problem.
     
    Last edited: Jul 11, 2018
    N8AFT likes this.
  7. KC8VWM

    KC8VWM Moderator Volunteer Moderator QRZ Page

    RG-316 is similar in physical characteristics, but has less attenuation loss than RG-174.
     
  8. N8AFT

    N8AFT Subscriber QRZ Page

    RG-174 seems to be more available though, may be something to consider.
    The two major ham equipment suppliers I checked do not stock the item.
    My very first HF antenna was made by Hy-Power. It was 20m and came sans balun.
    I worked the world with it despite its lacking a balun transformer. ;)
    K8JD is absolutely right.
    Those "Old Fashioned Ways" still work remarkably well in this present day es age.

    Learn Morse
    Do CW
    73
     
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  9. KU3X

    KU3X Ham Member QRZ Page

    When I set up portable and my coax runs are 35 feet or less, all I ever use anymore is RG 174. I use to always use RG 8X, but the difference is losses between the two was not worth the added weight and storage size. I either use a QRP OCF40 or one of my HWEF40's. I can put either antenna in my pants pocket. The same goes for the RG 174, fits in my pants pocket.
    When I use a dipole, for a balun, I use three turns of RG 174 around a #43 clip on ferrite bead.
    Don't want to put connectors on RG 174? Go to cables on demand.

    http://www.cablesondemand.com/produ...rs/Items/Library/InfoManage/CO-058BNCX200.htm


    I know you said you have a ferrite core, but if the connectors are already on the coax, you won't get it through the core. So a clip on is cheap and easy to use anywhere.

    http://www.mpja.com/025in-ID-Ferrite-Clamshell-EMI-Filter/productinfo/18466+FL

    Barry, KU3X

    http://www.ku3x.net/portable-qrp/elecraft-kx3
     
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  10. W4OP

    W4OP Ham Member QRZ Page

    RG-316 has more loss than Belden 7805 RG-174. At HF we are talking about hundredths of a dB. 316 is easier to work with because of the PTFE dielectric and jacket.
    Dale W4OP
     

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