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loop antenna feedline

Discussion in 'General Technical Questions and Answers' started by KB3SJQ, Mar 13, 2010.

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  1. KB3SJQ

    KB3SJQ Ham Member QRZ Page

    I am building a 160 meter (520 foot) horizontal loop antenna and I am wondering how to feed it. I have the option of feeding it with 450 ohm window line but I already have a 1:1 balun with 50 ohm coax hung at the intended feed point from a previous antenna. If I were to feed the loop with the balun instead of the 450 ohm window line would it still work well or at least half decently as a multiband antenna compared to feeding it with window line?
    Thanks in advance!
    73s de
  2. W8ZNX

    W8ZNX Ham Member QRZ Page


    a full wave loop cut to freq fed with coax
    is for the most part a mono band antenna

    if you want to use it as a multi band antenna
    feed it with open wire

    save the coax and balun for some other project

    yours truly
    mac dit dit
  3. K8MCN

    K8MCN XML Subscriber QRZ Page

    Feed it with the 450 ohm ladder line!
    here is how i feed mine--ladder line to the shack entrance exterior wall---female banana plug termination---two lengths of 75 ohm coax--male banana plugs on each center conductor. I tie the grounds shields together on each end and tie them to ground.........male banana plug to the ladder line termination and the other end of the 75 ohm to my Palstar tuner.
    In my experience, keeps the majority of the Rf out of the shack and the AT1KP has no trouble with the loop.
    Your mileage may vary, but this works for me.
  4. KA4DPO

    KA4DPO Premium Subscriber QRZ Page

    The feed point impedance is probably in the neighborhood of 100 to 200 ohms so the 1:1 Balun and coax will have some loss. I would use the balanced feed line and a tuner to keep the losses to a minimum.
  5. W2BBQ

    W2BBQ Ham Member QRZ Page

    Not true.

    I use one today and have had others in the past. Loop with 4:1 coaxial balun at feedpoint and coax works all bands, with resonance, up to 6 meters. First time every time.
  6. K8MCN

    K8MCN XML Subscriber QRZ Page

    with resonance??how?? and at what length? with no tuner? i dont see how-convince me please
  7. K0RGR

    K0RGR Premium Subscriber QRZ Page

    A full-wave loop will present a reasonable match to coax at the resonant frequency and all harmonics. 1.8, 3.6, 5.4, 7.2, 9.0, 10.8, 12.6, 14.4, etc..

    As you can see, if you cut it for 1.8 Mhz., it will probably give you a good match on 80, 60, and 40, too. If you cut it a bit long for 160, say for 1.75 Mhz., it should provide a decent match for 50 ohms in or very near all of the HF ham bands.

    The typical impedance of a loop in free space is 100 ohms. But, unless your loop is going to be at least a half-wavelength off the ground, the impedance will be lower, probably closer to 50 ohms. So, you can probably get by with a 1:1 balun or a simple choke balun at the feedpoint.

    Feeding it with open feeders will allow you to operate it at any frequency above the design frequency, and possibly a little more efficiently. However, your 160 meter loop may not be a great performer on the higher bands, anyway, because the radiation pattern breaks up into a set of lobes, which become sharper as the frequency increases.

    On 160, the loop will be a quiet receive antenna, but unless it is quite high, it will be an NVIS delight. You may want to consider a vertical for transmitting on 160 and 80, and using the loop for receiving.
  8. N0AZZ

    N0AZZ Premium Subscriber QRZ Page

    I use one with a 4-1 balun w/tuner amd it works fb on all bands. On the low bands for NA it is the best antenna I've used quiet but NVIS for transmit I use a vertical a HyTower w/160m kit top mount.
  9. A22EW

    A22EW Ham Member QRZ Page

    i concur with 4:1 balun and feed with 50ohm coax; i did not have the luxury of 450 ohm feed line.
    Build your own aircore 4:1 balun. It is very straightforward. I can send you the schematic - it will cost around 3$ to put one together as long as you can get hold of 2" wide white pvc pipe - 5" in length to wrap the coil.
    Send me an email with tel. no i can give you a call to guide you through. zs735 at
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