DB-212 6m Antenna

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KY4TPR, Sep 27, 2017.

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  1. KY4TPR

    KY4TPR Ham Member QRZ Page

    I came across a free antenna. By the looks of my model # (DB-212-2-B) & my research, it looks like another element is meant to accompany this antenna. I've found a helpful website that will allow me to retune it for where I want it: http://www.ccdx.org/zedyx/mods/db212.htm Also, I've found that Andrew bought out the original Decibel Products Inc. company and by the looks of their brochure, they have a single element model: http://www.repeater-builder.com/antenna/db/pdfs/db-212-catalog-sheet-(andrew).pdf

    Can I use this particular model as a standalone element or do I have to find another element to match? Thanks for the help.
     
  2. K2NK

    K2NK Ham Member QRZ Page

    Yes
     
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    It is a standalone; models with additional elements have different model numbers and require a much longer mast (or really a tower). The "B" can be tuned up to 42 MHz normally but with significant mechanical rework can be tuned to 52 MHz for 6m use.

    Each element on its own is 50 Ohms; when you combine two elements, they're combined using a splitter that steps up the impedance of each antenna to about 100 Ohms, them combines the two 100 Ohm loads in parallel to make it 50 Ohms again -- all done with critical lengths of 75 Ohm coax.
     
  4. KY4TPR

    KY4TPR Ham Member QRZ Page

    Awesome. Thanks for the replies. I'm looking forward to working this antenna into the 6m range; it's tuned to 45mhz so it's going to take some reworking. The best part is the antenna is in pristine condition and is from 1980.
     
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    They are surely well made.

    One of my old repeaters using the 2m 4-pole version of the same brand and general design has been up since 1977 and never serviced in any way -- works (and looks) the same as when it was new.
     
  6. K9STH

    K9STH Ham Member QRZ Page

    The actual feed-point impedance is well above 50-ohms, much closer to 300-ohms. Each antenna comes with a specific harness that matches the antenna to 50-ohms.

    The DB-212 series is an adaptation of the DB-201 antenna which has the "loop" plus 4-each tuned radials.

    The story behind the design of the DB-201 and the founding of Decibel Products is interesting. The late Jerry Stover, one of the 2-founders of Decibel Products, was a good friend of mine. Over the years, the tale that he told about why the DB-201 was designed got longer and longer and longer. It also got more humorous every time he told the story.

    In the period after World War II and well into the 1950s, in the Texas oilfields, many of the drilling rigs had a low-band (30 MHz to 50 MHz) ground plane antenna installed for two-way radio communications. Unfortunately, because of the vibrations from the drilling process, these antennas had a bad habit of losing the radials and those radials, of course, would fall to the ground.

    Although Jerry had been one of the design team that perfected both RADAR and radio control, after the war he went into the two-way radio field founding his own service company. As such, he often found himself in the field repairing the radio equipment and installations.

    One day, at a drilling site in east Texas, Jerry got out of his vehicle and a VERY large "roustabout" came up to him. The roustabout asked if he was the radio repairman and Jerry answered to the affirmative. Then, the roustabout physically picked Jerry up and carried him to a point near the drilling rig. Sticking out of the ground was one of the antenna radials. The roustabout held his forefinger and his thumb less than an inch apart and said, "The antenna missed my head by THIS much, FIX IT."

    Coming up with an antenna that could withstand the vibrations of a drilling rig was a daunting task. Finally, Jerry came up with the design of the DB-201 and started manufacturing the antennas in his garage. After installing the antennas on a few drilling rigs, the word spread about how well the antennas worked and were able to not fall apart when installed on the rigs. As orders came in for more, and more, of the DB-201, Decibel Products was formed and additional antenna designs were forthcoming. However, Jerry also enlarged his two-way radio service organization and established a radiotelephone company operating, in quite a number of cities, in the RCC (Radio Common Carrier) services.

    Of course, when Jerry told the tale, he embellished it, making it more, and more, colorful every time.

    Glen, K9STH
     
    AK5B likes this.
  7. WB0EMJ

    WB0EMJ Premium Subscriber QRZ Page

     
  8. WB0EMJ

    WB0EMJ Premium Subscriber QRZ Page

    could you please send me detailed measurements for this element as I want to build 4 of them I need the distance between the element and the mounting point it would be the distance between the tower and the element when mounted.I also need the distance between the folded dipole element , the measurement inside to inside of the U bend at the top or bottom. also need how the mount is attached and feed point a close up picture with notes would be great. hope you can help me out can't find this info any where.
    Thanks Stan
    WB0EMJ
    ssiems@mycns.net
     
  9. KY4TPR

    KY4TPR Ham Member QRZ Page

    Are you wanting the measurements as it is tuned to 45mhz? I haven't had time to change it to the 50mhz range yet.
     
  10. WA4SIX

    WA4SIX Ham Member QRZ Page

    I have a DB-201 in the shed that I should put up. Great antenna.

    Ed
     

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