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Adjustable Gamma match for mobile antennas

Discussion in 'CB Radio Forum' started by rabbiporkchop, Jun 27, 2016.

Page 3 of 7
  1. Jan 23, 2018 #21
    rabbiporkchop

    rabbiporkchop Road Train Member

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    If you have a bad ground it could explain some things and in that case the shunt coil wouldn't help.
    If you put a small value inductor in parallel with an inductive antenna or even a resonant one you're going to be disappointed... it'll make the match worse. To do the shunt coil thing you need to detune the antenna a bit higher than the desired frequency. Since it's so often used on screwdrivers, etc., people sometimes say that you should "resonate the antenna first and then install a shunt coil" but really you need to resonate it up the band a bit so that it's capacitive. The antenna element has got to be CLOSE to resonance... but not quite there.
     
    rabbiporkchop, Jan 23, 2018
    rabbiporkchop, Jan 23, 2018
    #21
    handlebar Thanks this.
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  3. Jan 23, 2018 #22
    craig_sez

    craig_sez Road Train Member

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    So i awag wire same as copper wire to try a shunt??
    Im thinkin my issue is ground but my.#'s have changed so its confused me seeing all my.trk connections were cleaned except my braided straps on my door hinge..Lately its either cold as duck or partly rain and part snow....
     
    craig_sez, Jan 23, 2018
    craig_sez, Jan 23, 2018
    #22
  4. Jan 23, 2018 #23
    rabbiporkchop

    rabbiporkchop Road Train Member

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    If X=0 somewhere in the ballpark, ground should be good.
    If X= can't even be close, it's probably a ground issue.
     
    rabbiporkchop, Jan 23, 2018
    rabbiporkchop, Jan 23, 2018
    #23
    skellr Thanks this.
  5. Jan 23, 2018 #24
    craig_sez

    craig_sez Road Train Member

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    Ground is pretty good then..Im in mid /low single digits..Im tryin to go mid way between 1 and 19 cause thats the 2 ch used the most in canada and usa..But i can get in low low singles on a ch if need be..
    Just trying to figure out if copper wire is all copper or your basic awag wire..
     
    craig_sez, Jan 23, 2018
    craig_sez, Jan 23, 2018
    #24
  7. Jan 23, 2018 #25
    rabbiporkchop

    rabbiporkchop Road Train Member

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    Coil won't work if tuned for 19
     
    rabbiporkchop, Jan 23, 2018
    rabbiporkchop, Jan 23, 2018
    #25
  8. Jan 24, 2018 #26
    craig_sez

    craig_sez Road Train Member

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    Never said im tuned for 19..Said im tuned between 1-19..
     
    craig_sez, Jan 24, 2018
    craig_sez, Jan 24, 2018
    #26
  9. Jan 24, 2018 #27
    Ridgeline

    Ridgeline Road Train Member

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    Just get 14 gauge wire, with a thin plastic coat on it, or bare, make the coil then spray it with some clear paint with it spear a part a little bit.

    You guys do know that the shunt does not need to be precise?
     
    Ridgeline, Jan 24, 2018
    Ridgeline, Jan 24, 2018
    #27
    rabbiporkchop Thanks this.
  10. Jan 24, 2018 #28
    craig_sez

    craig_sez Road Train Member

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    If i can get in a 45-55 ohm range i might be happy.I am a bit anal anout it now though..#### analyzers..
     
    craig_sez, Jan 24, 2018
    craig_sez, Jan 24, 2018
    #28
  11. Jan 24, 2018 #29
    rabbiporkchop

    rabbiporkchop Road Train Member

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    That's the whole problem. When it's inductive you need a magical capacitor which doesn't exist at a specific value but when it's capacitive then a simple piece of wire will work.
    If x=0 at a frequency lower than one that you plan on using then the shunt match coil will not work at that channel.
    X=0 needs to happen at a frequency higher than you plan on using in order for the shunt coil to be of any use.
     
    Last edited: Jan 24, 2018
    rabbiporkchop, Jan 24, 2018
    rabbiporkchop, Jan 24, 2018
    #29
  12. Jan 24, 2018 #30
    craig_sez

    craig_sez Road Train Member

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    In theory..Lets say im resonate at ch 17(what ever the freq is)but i should be fine with 19 or 1 with a shunt correct?...As tuned right now ch 1 is about 57 ohm and 19 is about 62ish..40 i think is at 67 ohms..I jjst wanna get it down so it doesnt affect my radios output or rec ....
     
    craig_sez, Jan 24, 2018
    craig_sez, Jan 24, 2018
    #30
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