A thread that will never die

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

  1. craig_sez

    craig_sez Road Train Member

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    Gotta watch that vid..I tried a version of that on youtube but they all made so techy and i couldnt grasp it..Ill try with that bid.....
    My rig expert has that smith chart option in it now that i think of it..
     
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  3. rabbiporkchop

    rabbiporkchop Road Train Member

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    You might find this interesting.
    LC circuits 101
     
  4. Ridgeline

    Ridgeline Road Train Member

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    yeah, thats good but there is one measurement used to determine the condition of the coax which is the most important test and no aa can do.
     
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  5. craig_sez

    craig_sez Road Train Member

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  6. Ridgeline

    Ridgeline Road Train Member

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    you need a signal source on one end and something to measure it at the other.

    It is a bit more complicated to figure out how well the coax is working, so I won't post the details.
     
  7. jammer910Z

    jammer910Z Road Train Member

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    18ft of coax is commonly used because it was the length from the dashboard of a 4wheeler to the metal bumper where they mounted that big antenna with the tennis ball and had it strapped down to the roof in the 70s.

    18foot.

    It's a D A M N SCAM

    4ft works if it's all you need.
    Good post
     
  8. Gadfly

    Gadfly Medium Load Member

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    Jammer's got it down! Strip away all the hype and pseudo-technical "experts", and coax is merely ONE thing: a means of getting your signal from point A to point B (antenna) where it can be distributed out to the world!;) Tha's ALL! And that little tidbit is where the "coax length" thing started...simply because it was what mfr's included in the package when 4-wheeler Cadillacs and Chevys were the rulers of the road. Big sedans. Because *most* users of CB were not technically inclined, they simply followed the instructions given in the package and use the parts therein--including the coax. Along the way, it was assumed that the included 18 feet was necessary for the system to work. IOW, it became "Bible truth" SFA CB was concerned! The only time a *certain* length became important was with phased or phased array beams or the popular CB co-phased antennas on big trucks.

    It makes it seem very technical, or very important to those who want to pretend they are much more knowledgable than the rest of us to spend time fiddling with velocity factor and just the "right" length of coax to get that O-n-n-n-n-n-n-e eensy extra watt out when that one eeensy little bit of RF will be undetectable on the other end. ---And that's fine if one want to do that. But, IMHO, and my experience shows me its a waste of time.

    I recently (and finally after the WX improved) got my 80-10M HF system in my pickup. From the bumper into the cab where the radio is remoted behind the back seat, its about....oh, 6-7 feet to the radio. The coax length is not related to ANYTHING. I'm making contacts on 75 and 40 Meters on a regular basis. We don't need no "stinkin'" ;) 60, or 30, or 14 feet of coax. It works fine on ALL bands with 6 feet!:D:D
     
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  9. Timin770

    Timin770 Road Train Member

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    On the other hand it's not a big challenge to do 30 seconds of math, cut 3 feet off and refit the connector. 5 minutes tops
     
  10. Gadfly

    Gadfly Medium Load Member

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    That's what I do!:)I measure out what I need to get to the radio and cut it to that length. In my case, it takes 6 feet--maybe 7--to get from the antenna to the radio. If standard antenna theory says one *must* have a certain length, then I'd have to have 60 feet to operate on 3923 KHZ. There's not ROOM in an S10 to "hide" all that!:D
     
  11. Slowmover1

    Slowmover1 Road Train Member

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    So, since length doesn’t much matter, the only REAL criterion is coax and connector quality.

    A few feet more than necessary — and AMPHENOL connectors — majes for those of us who order online an easy job.
     
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