Tuning the HyGain TH-1 or MFJ-1769

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KI4ZX, Oct 26, 2016.

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  1. KI4ZX

    KI4ZX Ham Member QRZ Page

    The identical HyGain TH-1 and MFJ-1769 each have to be tuned up before use. I recorded the final tubing lengths for my MFJ-1769 and decided to share them based on the assumption that it may save someone time tuning up his rotatable dipole. Otherwise, the iterative process can take a good while to complete. First, there is an ambiguity in the assembly manual. Make sure that the 10 meter trap is installed with the longer tubing facing toward the center of the antenna! Yes, that means only short tubes exist between the two traps. That’s not a problem since very little or no tuning must be performed between the traps.

    The dimensions I’m giving favor the voice portions of 15 and 20 meters and the lower portion of 10 meters. Starting at the middle of the dipole, I will call the first aluminum tubing on the fiberglass rod “Tube 1” and number consecutively going out. When adjusted, the visible portion of Tube 2 is 39.5 inches. Similarly, the visible portion of Tube 3 is 30.25 inches. The visible portion of Tube 4 coming out of the 10 m trap is 4 inches. The length between the traps is minimized (pushed tightly together). The outer-most element on the antenna is 23.75 inches for the voice portion of 20 meters. My antenna has no 6-meter element. Hope this helps someone.
     
    AK5B likes this.
  2. AK5B

    AK5B Ham Member QRZ Page

    While tuning may and often will vary somewhat over different ground your above post surely will get someone installing the same antenna into the ballpark a lot faster than otherwise. Thank you for a nice, helpful idea.

    73, Jeff
     
  3. KI4ZX

    KI4ZX Ham Member QRZ Page

    Jeff -- Yes, I hope you're right! I kept looking for dimensions for the tuned antenna on the web and, not finding any, decided that I would produce them myself and share them.

    Bob
     
  4. KI4ZX

    KI4ZX Ham Member QRZ Page

    Here is a further tweak: The distance between the two traps should be expanded 1/4 inch (from minimum) for a 1:1 match across the voice portion of 15 meters. This change did not affect 10 or 20 meters.
     

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