HF End-Fed Multiband that works well

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KK4NSF, Aug 12, 2019.

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  1. KK4NSF

    KK4NSF Ham Member QRZ Page

    The other day, one of my Ham buddies asked me how my signal got out as good as it does considering that I've only got 100w, and am using an end-fed random wire antenna. Well..... yes I do only have 100w, and my antenna IS end-fed, but it is NOT a totally random length. It's actually a carefully cut length, based on tests I did a few years ago.

    If you look at the attached sketch, you can see how it's configured. It is VERY similar to the "Magic Antenna" size (84' long w 17' counterpoise), but it does differ a little to accomodate the location. Here are the details:

    Length of radiating element: 72'
    Length of Coaxial feed line: 12'
    Length of Counterpoise: 0'
    Height in center: 25'
    Height at Shack: ~ 8'
    Height at far end: 15'

    Using my SWR meter, it tunes up from 75/80m to 12m at 1.2:1 with no problem, except for 30m and 10m which run about 2:1. That's goo enough for what I do.

    The thing you will notice is the Co-Ax feed line. That was NOT originally done for any RF reason. It was done to help insulate the antenna from curious folks who might accidently touch it, to maybe prevent them getting burned. However, I'm not sure that section of the antenna is actually radiating. The co-ax braid is grounded. Using a small neon bulb, it glows when near the open wire, but doesn't glow when near the coaxial part. What this proves is open for debate. SO..... IF it's radiating, then the antenna length is 84'. If it's NOT radiating, then it's 72' long. I do know that I don't have any RF in The Shack problems.

    The other thing you will see is that there is no counterpoise. Originally, it did have a 17ft counterpoise in addition to the grounding rods. Then one day I accidently cut it with the weed-eater.... and there was no change in how well it worked. So I never put it back on. BUT I must say that our ground here is wet and conductive, and I've got 4 long copper ground rods. I am sure that if I had poor ground, the counterpoise would be needed.

    So there it is: the KK4NSF variation on the HF End-Fed Antenna. It works well.

    (sorry about the rough sketch. It was drawn whilst riding in the car on a road-trip)

    Attached Files:

    KX4O likes this.
  2. KK4NSF

    KK4NSF Ham Member QRZ Page

  3. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    17ft of wire is not much of a radial, as you have proven. If you installed one or more radials of significant length, your efficiency would markedly improve.

    Even wet soil is a poor RF conductor. Copper wire is over 1,000 times more conductive. That is why we use radials.
    AK5B likes this.
  4. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    P.s. radials fanned out under the antenna would work best if you can't lay out a whole pattern.
    AK5B likes this.
  5. AK5B

    AK5B Ham Member QRZ Page

    While many think that RCA stands for Radio Corporation of America I know it actually means Radial Coalition of America...
    K0UO and KK4NSF like this.
  6. KK4NSF

    KK4NSF Ham Member QRZ Page

    We'll have to agree to disagree on that one. A few years ago I ran a whole series of tests on the "counterpoises for random wires" question (see the link above) and also for vertical antennas. From What the real world tests show me, they are VERY important for verticals, but not nearly so much for long random wires.

    Also ref https://udel.edu/~mm/ham/randomWire/ and https://www.nc4fb.org/wordpress/w3edp-multi-band-antenna/

    Building upon those designs, I've come to the conclusion that for this type of antenna, radials are not as beneficial as folks would seem to think.
  7. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Yes I remember the W3EDP hoopla.

    Again, a 17 foot radial will not be very effective with an 84ft antenna. However, that does NOT prove radials are ineffective nor that this is a Special Case" antenna which defies the laws of electricity. Sigh.

    Unfortunately I am unable to model this for you at the moment.
  8. KK4YIV

    KK4YIV Ham Member QRZ Page

    Which MFJ tuner are you using and where is it located?
  9. KK4NSF

    KK4NSF Ham Member QRZ Page

    it's a MFJ-917, located at the transciever end of the coax feed-line.
  10. AI3V

    AI3V Ham Member QRZ Page

    If your wire tunes to 1.2:1 why are you using a tuner?

    Also details of your "neon bulb" test, I have never been able to illuminate a neon bulb at hf.

    Even running 40,000 watts at a navy relay station.


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