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Is a Choke Balun Needed Under an AH-4 Antenna Tuner for Inverted "L" Antenna?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by WA3MOJ, Oct 12, 2018.

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  1. WA3MOJ

    WA3MOJ Premium Subscriber QRZ Page

    .
    Progress on the tuner antenna project is being made slowly but surely.
    For those never attempting this sort of project, please bear with me.
    Life's demands seem to keep getting in the way of fun ham radio projects !!

    Terminations have been made on the control cable with a 4-pin Molex connector.
    This is the Icom style that has the same 4-pin configuration as on the back of later
    Icom radios where the AH-4 tuner connection is made.

    The coax was terminated with a PL-259 male connector and a UHF female barrel
    connector attached to the PL-259.

    The purpose of both of these connectors is to facility easy removal of the AH-4 antenna
    tuner, rather than hard wiring-in these into the AH-4. Otherwise the cables would need
    to be cut for removal of the AH-4 from the system.

    Next. . . . we will bolt the AH-4 antenna tuner inside the black enclosure box and then bolt
    the aluminum angle to the bottom of the enclosure box. Holes will be drilled into the
    aluminum angle, which will then act as a connection point for the ground radials.
    .
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    Attached Files:

  2. WA3MOJ

    WA3MOJ Premium Subscriber QRZ Page

    .

    Meantime, I can begin to prepare the ground radials, by cutting the wire to length and soldering several on to a copper grounding lug (ring terminal). Maybe 3 wires per lug. These will then be bolted to the aluminum grounding bus under the black enclosure box, then buried from there.

    Remember, a single ground rod is not enough to be considered a sufficient ground. Even though some other manufacturers of vertical antennas claim it's fine, the fact is the more radials that can be buried the better the antenna will perform.

    For the radial wires I'm using whatever wire I have on hand. In this case I plan to install at least 12-15+ buried radial wires using #14 solid copper wire and #12 stranded, both insulated. We'll see how much room I have and how many will be buried as the installation progresses.

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    Attached Files:

    KD6RF likes this.
  3. WA3MOJ

    WA3MOJ Premium Subscriber QRZ Page

    .
    Several radial wire "bundles" were prepared (soldered), using 3- #12 stranded wires into a single large ring terminal.
    Several more radial wire bundles will also be made using #14 solid copper wire (not shown).
    These ring terminals will then be bolted to the aluminum angle grounding bus.
    As previously mentioned, use whatever wire you have on hand.
    In addition, 2- large lugs were soldered onto heavy #2 copper wire for each of the 2 ground rods.

    .
     

    Attached Files:

  4. AA7QQ

    AA7QQ Ham Member QRZ Page

    I have galvanized 14 Ga. rabbit fence laid under walkways. Provides a good coupling to ground.
    I even have them irrigated with copper clad dripline.

    Ed
     
  5. WA3MOJ

    WA3MOJ Premium Subscriber QRZ Page

    While mounting the AH-4 tuner into the black enclosure box, provisions need to be made for the antenna wire to exit by drilling a hole in the top of the enclosure. The bottom of the tuner has the (negative) grounding terminal for the radial wire connection. For this application, I fabricated a short piece of #8 solid copper wire with a lug (ring terminal) soldered on each end and one in the center. The center lug connects to the tuner grounding terminal, while the two ends are bolted to the aluminum angle bolts.
     

    Attached Files:

  6. WA3MOJ

    WA3MOJ Premium Subscriber QRZ Page

    .
    As I mentioned before, the black First Alert locking security box is a perfect fit for the AH-4 antenna tuner.
    Although it is not exactly weather tight, I have an idea that will keep it completely weather tight.

    In the plastic storage box aisle of your favorite big box store or super-center, I found a 15 quart plastic
    storage box with a latching lid.

    As the AH-4 antenna tuner fit perfectly into the black enclosure box, now the enclosure box fits perfectly
    into this plastic storage box. The latching lid is an added plus, since the cover can be opened or closed at
    will to check on the interior of the grounding and tuner components.

    Ultimately the plan is to mount this assembly to the outside building wall, as was previously shown in a
    proposed pictorial sketch diagram.
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    Attached Files:

  7. WA3MOJ

    WA3MOJ Premium Subscriber QRZ Page

    .
    As previously mentioned, the antenna will be in the configuration of an Inverted "L" with a total wire length of 43 feet. Based on my existing conditions, the approximate vertical length of the wire will be ~ 23' and the remainder traveling horizontally.

    In this situation, the method of mounting the actual antenna wire to the outside building wall at the point where vertical becomes horizontal is shown in the attached photos. First, the antenna tuner will be mounted at the base of the outside building wall. The antenna wire exits the top of the tuner enclosure and up to a wood dowel that is fastened to a 90 degree metal angle bracket. The metal bracket will then be fastened to the outside wall of the building. The dowel will further be glued and encased to the bracket in an exterior grade adhesive. A hole drilled on an angle at the tip of the wood dowel allows the antenna wire to pass through and change to the horizontal direction.

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    Attached Files:

  8. WA7F

    WA7F Premium Subscriber QRZ Page

  9. WA3MOJ

    WA3MOJ Premium Subscriber QRZ Page

    .

    The next step of the AH-4 antenna project is to bury the ground radial wires. However, it's becoming increasingly difficult trying to coordinate a dry day with my available time. I'd like to do this on a day were my shoes do not leave a permanent imprint in the ground. This past summer season has pelted us with an incredible amount of rain. Our area has seen more precipitation than in recent memory and it seems like it's raining almost every other day.

    The project is still a go, but the ground needs to firm up a bit more. Attempting to bury the ground radial wires at this time would create a muddy mess.

    Meantime, the wood dowel and metal angle bracket assembly to be mounted at the vertical most section of the antenna has been treated with several weather resistant coatings and is ready for wall mounting.

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    Attached Files:

  10. PA1ZP

    PA1ZP Ham Member QRZ Page

    Hi

    Yes a RF choke is needed.
    And yes we will be in debt at G3TXQ for ever.
    His list makes things easy and understandable.
    And his list shows that an ugly air core balun can work wonderfully on just 1 or maybe 2 close in frequency bands.

    There is another way that almost nobody mentiones .
    That is burry the coax over 2 feet deep in the ground for over a length of 10 yards or more.
    But then again a good 1 : 1 current balun is always good and willl not hurt a soul.
    I use many of Steves G3TXQ designs at different places on different antennas at my home.

    Far more important is building an antenna with a good design with low losses and good radiation patterns.
    You can always ad a balun, adding a golden balun at a superimposed highly calibrated supercritical carbon enforced titanium platinum infused dummyload will not make this antenna work at all.

    73 Jos
     

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