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Log-Periodic Antenna Design

Discussion in 'Electronic Design' started by Rich Grise, Nov 19, 2008.

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  1. Cecil Moore

    Cecil Moore Guest

    My Webster's unabridged dictionary gives the following
    examples of the correct way to pluralize numbers.

    "figure 8's", "the 1890's", "the 20's"

    73 is a number that stands for "Best Regards"

    73's would be "Lots of Best Regards".
  2. Cecil Moore

    Cecil Moore Guest

    If you are a member of IEEE, you can access this paper:

    Multiband behavior of wideband Sierpinski fractal bow-tie antenna
    Yamini, A.H.; Soleimani, M.
    Microwave Conference, 2005 European
    Volume 3, Issue , 4-6 Oct. 2005 Page(s): 4 pp. -
    Digital Object Identifier 10.1109/EUMC.2005.1610336
  3. Cecil Moore

    Cecil Moore Guest

    I've not had any problems with the UHF circular loop
    that comes with standard rabbit ears. The only problem
    I've had is with VHF channels on the dipole. I need
    a weatherproof version of my RS rabbit ears.
    Unfortunately, ABC is Channel 7 here in Tyler, TX.
  4. Dave

    Dave Guest

    I don't have time to search for it, but there's also a dual quad UHF TV
    antenna that's easy to build with the same kind of materials. I prefer
    steel tie wire to coat hangers because it's easier to work with.
  5. mpm

    mpm Guest

    Now that the FCC has given a green light to whitespace device
    deployments (particularly those that rely solely on spectrum-sensing
    technology), you may find you need a better antenna than a simple
    loop, bowtie or coat hanger.

    For those of you who are not following the issue, a quote in this
    week's TV Technology pretty much sums it up:

    "MSTV (Maximum Service Television) told the Commission Oct 31 that the
    least the FCC could do is subject the devices to rigorous testing
    beforehand and ensure fair and reliable tests to prevent interference
    to DTV. In a filing, MSTV also attacked the FCC proposal that a
    device should be able to detect signals as low as -114 dBm, a level
    MSTV equated with setting a smoke detector to only be able to detect a
    raging fire."

    Whitespace devices will also cause great harm to wireless microphones,
    particularly older models.

  6. GregS

    GregS Guest

    I don't have data. I think the home made TV antenna in the video, is very much like a bow tie,
    and could have better bandwidth by making the elements different lengths. The gain factor
    is going to be narrow band since the feed length is constant. I would have also used 12ga
    copperweld or solid copper. You can also get closer to fractal by using many more different
    sized elements.

  7. Charlie E.

    Charlie E. Guest

    Well, they work if you have a good, strong, signal, but if you don't

    Here in the desert, all the stations are co-located only about 6 miles
    from here, but there are two little problems. One, 80% of the valley
    population is located to the south, so they have configured the
    antennas with their major lobes that direction, and second, there is a
    Edmom Hill between us and the antennas! You can't even get analog
    broadcasts here, much less digital!

  8. JB

    JB Guest

    If you are a member of IEEE, you can access this paper:
    And if you aren't a member, you aren't in on the joke?

    With all the added capacitance to the elements, I have little doubt that
    there would be lots of resonance's, and it would be cool to choose the
    geometry to bring about the proper feed point impedances, but these things
    can never be gainful with all the losses introduced.

    Neat idea for specific applications like little pocket toys, but certainly
    not the answer to everything.

    I wonder how the Limo's will deal with DTV in motion.
  9. JB

    JB Guest

    I don't have data. I think the home made TV antenna in the video, is very
    much like a bow tie,

    Comparable to a 4 bay bowtie. Maybe 6db gain. Brazing rod would be a
    little lighter and wouldn't rust. Would work much with a reflecting plane
    and above the house clutter.

    Twin lead could make a comeback since there won't be such a worry about the
    low band interference issue. Actually much less loss than coax. I may yet
    change over to 300 ohm window line on my bigazz deep fringe at 40ft and
    switch it to the ham shack for 6/2m SSB work and DTV DX. TV DX won't be
    dead, you will just have to know where to find it
  10. GregS

    GregS Guest

    Last time I used twinlead, except for fiddling around, was on the family
    TV antenna installation using an Allied Radio Corodized VHF antenna,
    with Beldon Super Permaohm 300 ohm shielded twinlead. Good stuff.

  11. Rich Grise

    Rich Grise Guest

    The only "evidence" I have is a "testimonial" by the guy who invented it,
    on some PBS show. And they claimed that that's how they pack so much
    antenna into a box the size of your thumb. ;-)

    And, having a passing familiarity with fractals, it just sounds eminently
    plausible to me. :)

  12. Art Unwin

    Art Unwin Guest

    Their advertising budget suggest that they are getting sales and they
    do radiate
    to the satisfaction of their users They don't have lumped loads so
    where ';s the beef?
  13. Rich Grise

    Rich Grise Guest

    Where I'm sitting here in Whittier, KABC 7 is so strong I can get it
    without even a cable plugged in!

    It's 50, 56, and 58 I worry about; 2-13 and 28 are covered; I'm looking
    forward to seeing if my new bowtie (from that youtube video, but with
    ER708-2 x 1/16 filler rod) will pick up PAX on 30. They have some nice
    oldies sometimes. (I also have some of the ER708-2 in 0.045".)

    I'm gonna solder it together and hold it to the board with brass thumb-
    tacks. ;-)

    Just for reference:

  14. mpm

    mpm Guest

    It's a folded, folded, folded, folded, folded,... n(folded) unipole
    antenna!! ;-)
  15. mpm

    mpm Guest

    Decent power, line of sight (18.2 miles @ 172.2 deg true) will do
    Check your email....

  16. John Smith

    John Smith Guest


    I am ready to bend over backwards, until I can say different ...

    However, how much you wanna' pay me for one of these?

    | <<-- telescoping whip
    |--------------------- <<---
    / |-------------- coax
    \ |_______________ <<--
    / <<----- 50 ohm, five-watt or better non-inductive
    \ |
    / |
    | |
    ----- ---
    --- - <<-- ground

    Lifetime antenna, virtually perfect SWR, no moving parts, guaranteed a
    lifetime, etc., etc.

    AND! I bet I can find some to give testimonials to it being an
    "excellent antenna." You know the game ... idiots are easily taken
    advantage of ... :-(

    .... come on, argue something real ...

  17. Ahah! Presently they don't. A big issue for opponents of 8VSB modulation
    was poor performance in mobile/handheld (M/H) applications. Straight 8VSB
    does not handle "dynamic multipath" well.

    However ...

    Development of the ATSC-M/H Standard for mobile
    and handheld applications is moving forward at a
    rapid pace. A critical element of that effort is the
    Independent Demonstration of Viability (IDOV).
    The goal of IDOV is to ensure that the technical
    proposals under consideration can meet the goal
    of enabling mobile and handheld services in early

    per -

    I read some news accounts of supposed successful tests (the "IDOV" ?) this
    past spring. We'll see.

    BTW, newsgroup is doing a good job with the TV
    transition. Also, has news, like
  18. Dave

    Dave Guest

    The FCC and the TV broadcasters looked the other way because there is no
    evidence that such activity has ever caused any interference. I can get
    6 microphones to work in an occupied analog TV channel and neither
    notices the other.

    The TV Band Devices the FCC has recently begun the process of
    authorizing are way more damaging than a 50 mW 65 kHz deviation FM signal.

    Luckily, these devices will not be allowed anywhere near where I work.
    The FCC has banned them from the 13 biggest cities, and from within a
    kilometer of a venue or stadium using wireless microphones. The
    proposed rules do not require a Part 74 license for these protections.
  19. Dave

    Dave Guest

    Ion TV 30 is in Claremont and has a 3.8 Megawatt Signal (elliptically
    polarized no less). It should give you a tan in Whittier.
  20. Jim Lux

    Jim Lux Guest

    interesting paper..

    The big benefit (from a cursory reading).. is that you have a more
    consistent antenna pattern over the frequency range, which the vanilla
    bowtie does not. And a somewhat wider match bandwidth. (mostly extending
    it to higher frequencies)

    Nothing magic, though.
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