A thread that will never die

Discussion in 'CB Radio Forum' started by Gadfly, Jan 18, 2019.

  1. Ridgeline

    Ridgeline Road Train Member

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    About 99% of the people - EVEN HAMS WHO HOLD EXTRA TICKETS - DO NOT understand what Standing Wave Ratios (SWR) means or how it is only one measurement in a line of a few to determine antenna performance.

    MOST at best guess what it is and ignore the warning that it isn't always important in an antenna system.

    Coax, aka feed-line has something to do with it, but not a whole lot.

    However I am of the 18 foot crowd not because there is a 'correct' way of determining what is the right or wrong way to create a feed-line for good antenna performance but because it is a simplified way of explaining to people who are not able or want to understand it without getting too complicated - i.e. smith chart and formulas. Hence, they sell it in 18 foot lengths, use that and see where it leads.
     
    Slowmover1 Thanks this.
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  3. rabbiporkchop

    rabbiporkchop Road Train Member

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    True, although if the feedpoint impedance is 47 ohms, this is where the can of worms gets opened. Since the objective is to present a 50 ohm load to the transmitter, and in a mobile installation impedance varies at different points throughout the cable due to the feedpoint never being a purely resistive 50 ohms, this causes some folks to use impedance transformers to fool the transmitter into seeing something that doesn't exist or using impedance repeaters to allow the transmitter to see what is actually real at a single given frequency.
    (They both work to a point)
    Currently I'm using a random length of cable. Probably 195° phase angle.
    If multiple people are talking simultaneously, I hear a heterodyne sound and am unable to hear all the individual voices. With 180°, I'd be able to hear all the separate voices like being in a crowded room. I'll be replacing my new LMR400uf cable soon with another 180° piece so I can restore my receiver to what it once was. Would the average person notice the difference? Not in a lifetime with a stock receiver. When people say it makes no difference, they are telling the truth as they know it to be true based on their personal experience.
    I've got plenty of videos showing my receive with 180° of cable before my antenna broke off. I've got a few since then after replacing the cable with a random length, and the heterodyne effect is only present when I use a random cable.
     
  4. craig_sez

    craig_sez Road Train Member

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    180 deg?? I dont understand that term relateing to coax....I know you dont mean 180 ' of coax..
     
  5. tucker

    tucker Road Train Member

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    Peak an tune it too !
     
  6. craig_sez

    craig_sez Road Train Member

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    Peak n tune dont help sweet eff all when a person has a poor ant set up..
     
    Crude Truckin' and rabbiporkchop Thank this.
  7. rabbiporkchop

    rabbiporkchop Road Train Member

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    Yes I do.
    [​IMG]
     
    Last edited: Jan 19, 2019
  8. craig_sez

    craig_sez Road Train Member

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    Ok..Get me a road map cause im lost..
     
  9. Ridgeline

    Ridgeline Road Train Member

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    You're not the only one.

    It has to do with how the signal travels down the coax and how the phase of the signal gets twisted around and cancels each other.
     
  10. rabbiporkchop

    rabbiporkchop Road Train Member

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  11. craig_sez

    craig_sez Road Train Member

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    I dont think thats in the mfj dorections booklet i got..If i did i dont remember it..
     
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