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Question about tuning a 'MyAntenna' EFHW

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KI5PPQ, Jun 30, 2021.

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  1. KI5PPQ

    KI5PPQ XML Subscriber QRZ Page

    The MyAntenna brand is well established with many proponents. I have never seen instructions on how to tune the antenna, however. In the event that it matters, I am interested in the EFHW-4010-2K-Plus. Is there a pdf or other resource to which I may refer?
  2. WA7ARK

    WA7ARK Ham Member QRZ Page

    The relationship between an 40m EFHW's fundamental resonance and its three harmonics is complicated. You might learn something by reading what I just posted here:

    or by viewing the slide show linked to at the bottom of my QRZ page.

    The 4010 is already "compensated", so you should not have to do much. Before you do anything, put it up, and measure what frequencies all four of its Swr50 minimums land on at 40, 20, 15, and 10m. Only after seeing those numbers, could I suggest what to do to the main wire.

    Who knows, after reading the linked article about the ARRL kit, you might decide to save $$$ and build one from scratch ;)
    Last edited: Jun 30, 2021
  3. KI5WW

    KI5WW Ham Member QRZ Page

    There are no instructions. They are closed now, but when they were open they would correspond via email only which actually worked. Just shorten or lengthen on the far end away from the transformer by checking SWR. Careful not to loose hardware in the grass. I used plastic bowls and was very careful not to loose any parts or tools in the grass. Three adjustments of 6 inches is what mine needed. 100 feet of coax seemed to help tame things down a bit.
    This was for the 7510 model not the 4010. Mine is the 2k plus. I’m very satisfied with it. When they reopen I’m going to order the 4010 2k to run opposite direction of the 7510 up now.
  4. KI5PPQ

    KI5PPQ XML Subscriber QRZ Page

    Thanks for the replies.

    So, simply stated, it is my understanding that, to start, the antenna I referenced would be adjusted in length (probably, shortened) to bring the SWR down to the lowest possible on the target frequency on the 40m band. How then does one go about tuning the antenna to the target frequency on the other 3 bands without having a negative effect on 40m?

    It would seem to me that a compromise would be required. That is, for example, the operator would have to choose his primary band and adjust the length of the wire to accommodate the target frequency on that particular band and then have to settle for how the SWR shakes out on the other bands. Is this pretty much how it works?
  5. KI5WW

    KI5WW Ham Member QRZ Page

    You adjust one it adjust all of them. Mine just fell in line after making the three adjustments mentioned. But during that process I emailed them and the quickly responded. Adding 50 feet of coax helped out a lot. I had to shorten mine and add coax. They do not like short runs of coax. Shipping was 2 weeks. I was and still am satisfied. Setting up an account is a must. I think they are reopening July 24. Remember I am referring to the 7510 2k. But I think they all pretty much the same.
  6. KI5WW

    KI5WW Ham Member QRZ Page

    Oh forgot to mention. Mine is installed as an inv V. Had to bend one leg about 80 degrees.
  7. WA7ARK

    WA7ARK Ham Member QRZ Page

    If you are designing the antenna from scratch, there are four "variables"; the length of wire from the transformer to the compensating network, the inductance/capacitance in the network, and length of wire from the network to the end. When optimizing the 40-10m antenna I linked to, I let the antenna simulator's optimizer play with all of those variables at the same time.

    If you are tweaking a store-bought antenna with a pre-installed compenstation network, chances are that everything you need to do will happen just by tweaking the wire beyond the network...
  8. KI5WW

    KI5WW Ham Member QRZ Page

    When I said I had to bend one leg I mean the last 15 feet of the end that is adjustable.
  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I guess since the advent of solid state transceivers, people are consumed with SWR and matching.:)
    W4HWD likes this.
  10. WA7ARK

    WA7ARK Ham Member QRZ Page

    I haven't found it particularly consuming... You just have to think about what you are doing a bit more. If you cant think, you can always build a "doublet" and spend the rest of your life twiddling knobs. :D
    KI5OMM and K1LH like this.

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