ad: UR5CDX-1

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

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

ad: L-HROutlet
ad: l-rl
ad: L-MFJ
ad: Left-3
ad: Subscribe
ad: Left-2
ad: MessiPaoloni-1
ad: l-assoc
  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.

    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
    KC8VWM likes this.
  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.

    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.

    Barry, KU3X
    N8AFT and KC8VWM like this.
  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

Share This Page