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Not to start an arguement just some thin s Ive learned over time.

Discussion in 'CB Antennas' started by Grim Reaper, Sep 29, 2011.

  1. Needle Bender

    Needle Bender ...he thinks it's funny that I stepped in it

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    Closer would be 70.7ohm coax (squared) = 4998.5 / 50 = about 100ohms, but it seems like I recall reading that 75ohm coax is actually closer to 72ohms.


     

  2. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    I see your point NB, thanks.
     
  3. bob85

    bob85 Supporting Member

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    eddie,
    it would be unusual if the display did not sit on conductive rubber strips, most lcd displays work that way,
    over time they get contaminated from airborn crud,
    all it takes is a slight bit of resistance and the polarising angle of the segment changes, sometime the bad segments can look ok when you tilt the display to a different angle,

    if you can get at the screen look to see if its sat on rubber,
    if it is, clean both edges of the rubber, the glass where the rubber makes contact and the contacts on the board with alcohol, then reassemble without touching the contact parts with your fingers,

    if its not sat on rubber strips you are unlucky,

    doc correct? surely not, let me go look at this, i don't believe it lolol
    good luck.
     
  4. Navionic

    Navionic Member

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    Were this argument to be true, all military applications would co-phase their antennas. You'd see antennas on towers on either side, or better yet, quad phasing on all four sides. Your cell phones would have dual internal antennas. Radio stations would place two antennas, etc... I worked on the antennas and arrays on aircraft carriers on top of the towers along with the radios on the birds and there is no way dividing the wave across two antennas would provide a benefit. The only benefit on a vehicle is due to placement on certain applications, due to the available ground plane. One 102" whip on the front lip of a bed on a truck will outperform any two antenna setup. May not look as cool, but it will work better. Lockheed Martin and Motorola equipment all seem to disagree with your premise.
     
  5. triple nickel

    triple nickel Active Member

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    Ok Sonny Boy, Hand me my Screwdriver.
    What ya need that for Pa ??
    I need to fix this Antenna Problem.
    See Sonny Boy, Everything works better
    When you put a Screwdriver to it !!!
     
  6. ghz24

    ghz24 Member

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    Faulty logic

    The military,commercial radio towers and cell phone makers want omnidirectional reception not directionality.
    For these applications the user would have to face the tower, ship or plane to benefit from the higher gain. And radio towers would leave half the audience in a null and out of luck.
    Two antennas co-phased can and do outperform a single antenna, it's called a phased array.
    Co-phased antennas are by nature directional because signals that arrive at both antennas at the same time(broadside or forward and backward if the antennas are mounted on the mirrors) are added together and signals that arrive at different times/angles are not added because the peaks arrive at different times
    If they arrive far enough out of phase/time they subtract and cancel each other out.
    At ~18 feet apart (for CB frequencies) the signals that arrive from side to side cancel out and leave a deep null


    [​IMG]

    This is the pattern as twin dipoles are separated from 2 feet to 22 feet.
    the value of "sep" is the distance of both dipoles from the center point in inches. So sep = 12 is 2 feet apart.

    The dipoles are at 0 and 180 degrees (12 and 6 o-clock)
     

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