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Best type of coax?

Discussion in 'General CB Services Discussion' started by Brian G, Feb 26, 2021.

  1. fourstringburn

    fourstringburn W9WDX Amateur Radio Club Member K5KNM

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    Disregard what Freecell says, That's untrue.


     

  2. freecell

    freecell Member

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    rf-9913 and lmr-400 have the least amount of loss due to line attenuation of any of the other feedlines mentioned in this thread coming in @ .65-.67 dB. loss per 100 feet @ 30 mhz..

    @ 100 mhz,
    rg-400 comes in at 4.4 dB. loss
    https://www.pasternack.com/images/ProductPDF/RG400-U.pdf

    rg-213 comes in at 2.2 dB. loss
    rg-214 comes in at 2.2 dB. loss
    rf-9913 comes in at 1.4 dB. loss
    https://www.w4rp.com/ref/coax.html

    lmr400 comes in at 1.2 dB. loss
    http://microwavecomponentsinc.com/data/TIMES/LMR-400-FR DATA SHEET.pdf

    all loss figures are per 100' ft..

    the meaning of the word "best" for my purposes when it comes to selecting feedline is a double shield for an additional 50 dB. + of rf shielding attenuation (from external currents and fields) and the lowest possible amount of line loss due to attenuation, guaranteeing that as much of the transmitter power as possible is delivered to the antenna load and as much of the received signal as possible makes it to the receiver front end, all the while limiting line loss to less than 0.5 dB. for long runs up to 78 feet in and around the 10, 11 & 12 meter bands.

    given a perfectly matching antenna load and a length of feedline with only .456 dB. of line loss, based on 100W. of input power in the citizens band, 10% or 10 watts are gone before the power makes it to the antenna load, leaving 90W. to be radiated. however much of that is actually radiated will depend on the radiation efficiency of the antenna itself. that might be something you want to think about, or not.
     
    #17 freecell, Feb 26, 2021
    Last edited: Feb 27, 2021
  3. fourstringburn

    fourstringburn W9WDX Amateur Radio Club Member K5KNM

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    Once again Freecell uses a dB spec at a very high frequency to make his point look better. LMR is much better at VHF and UHF frequencies because that's what it was designed and intended for. There is still even better cable to use for those frequencies too.

    Once again, at HF and below the losses are minimal between the two and RG213 has the solid copper wire for better voltage transmission power at lower frequencies. That is what RG8 type cable was designed and intended for.

    At 10 MHz, the center of the HF band with 100 watts at 100 ft, simple real world losses in power in the transmission line are as follows:

    Belden 213 losses equal 86.652 watts

    LMR 400 losses s 91.559 watts.

    Wow! we must all replace are crappy RG8 type coax and do what Freecell says and get LMR 400 so we can sleep better at night knowing our new coax gains us 4.9 at 100 watts in the transmission line! Not quite half the power loss as Freecells leads you to think by using a dB factor at a much higher frequency is it?

    But, using Freecell's manipulating way of making a point look better I'll use 1 Mhz at 100 ft and 100 watts.

    Belden 213 = 95.673

    LMR400 = 97.265

    Now we're talking a 1.592 watt difference.

    Freecells figures would be correct at 400 MHz for a near 2 dB loss between the two type coax cables. The losses are significant on both types at UHF frequencies and beyond.

    Belden 213 = 34.177 watts @ 4.663 dB loss

    LMR 400 = 55.891 watts @ 2.527 dB loss




    Next will be velocity factor difference and how 66 percent with 213 will slow your radio signal down. Don't laugh because I actually heard some CB base stations discussing this so it must be true!
     
  4. fourstringburn

    fourstringburn W9WDX Amateur Radio Club Member K5KNM

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    Yeah, if you prefer to make your own and often do, a ratcheting crimper with dies for the coax you is best for a solid and proper crimp on the shield. These can be found for under $60 with dies.

    I couldn't find a single die with both rg8 and rg8x on it so I have 2 dies to cover both types.

    Quality silver teflon connectors with a crimp shield and large hole solder tip as important too. Stay away from those pin hole looking tip connectors. I don't see how these can be properly soldered. The good connectors have a open tip similar to the all solder type.
     
    Slowmover likes this.
  5. Robb

    Robb Yup

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    Least resistance and capacitance are important characteristics to consider. Not to mention center conductor deviation vs bend radius.
    So is running the best antenna you can afford, especially if you need your coax run to be greater than 50 ft..

    But one coax quality is overlooked; its resistance to UV radiation. Also, its shielding. Ever look closely at a piece of Tandy RG-8 coax? Soooo little shielding and UV protection that it loses enough power over enough length to qualify it as a dummy load. Bake it in the sun for a couple of seasons and just see how pliable it is before it cracks open like an egg shell. Then replace it with a good piece of coax and note how much your receive improves, as well as SWR. Been there yet?

    SWR inconsistencies - that I have encountered - were mostly caused by poor or broken solder joints in the connectors that make for an intermittent connection. Mostly in mobile situations; but not limited entirely to it.
     
    Slowmover, HomerBB and freecell like this.
  6. bob85

    bob85 Supporting Member

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    There is no best coax, just the best for what you need it to do, or the best you can afford that will get the job done, they each have pros & cons,

    real rg213 is medium loss & tough as old boots, how i use my 213 it needs to be though,
    bend it tread on it run over it with car throw it around yard while i mow the grass bury it leave it in sun snow year after year at least 18 of them,

    I was going to change it before i checked the match & loss against a new role of 213,
    it still works with good vswr & normal losses, still clean & shiney copper inside,

    I also use coax with half the loss of 213 & better shielding for vhf/uhf but its no good for my 27mhz setup because i can't abuse it like 213,

    I won't use foam coax outside, its far too fragile,
    my buddies mini8 shorted out in the sun due to not having enough support points,
    the cb shop stuff bleaches in sun & goes brittle,

    what's best for you is probably not best for me.
     
  7. guitar_199

    guitar_199 Sr. Member

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    I'm in the gang that says .... no absolute answer.
    When I am looking.....I go for....

    1) lowest loss,
    2) power handling that suits my needs,
    3) endurance that works for what I need,
    4) for a price I am willing to pay.

    You can get incredibly low loss...but you will have to pay more to get it.
    Only you can decide when you are willing to compromise on any of these factors and to what degree you are willing to compromise and how much you are willing to pay.

    If you only shop for the lowest price...and that is all... the other factors will suffer.
     
    Unit 194 and freecell like this.
  8. freecell

    freecell Member

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    i'm not dropping almost 25% of my tx power across a new 100' line of 213. that's not happening.
     
    #23 freecell, Feb 26, 2021
    Last edited: Feb 26, 2021
  9. jkp1

    jkp1 Active Member

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    I just got a new antenna for the CB in my pickup. Belden RG8X seemed like an appropriate coax for that application.
     
    freecell, Slowmover and Dmans like this.
  10. AmericanEagle575

    AmericanEagle575 Sr. Member

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    I use RG 213 hooked up to a antron 99 ,it's only a 30 ft run from the antenna to the radio,and I haven't had a problem yet,flat 1.0 swr on 1 and 40,and it seems to hold up to the weather better then the Rg 8 I used to use!!
     
    Slowmover likes this.
  11. Slowmover

    Slowmover Elmer

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    I’ve just ordered for the Peterbilt a Belden co-phase harness with Amphenol ends from Bobs CB. Hopefully the assembly is up to brand-name type price.

    OTOH, none of it is exposed to the elements and it’ll be fitted inside flame-resistant split-loom tubing for some GP abrasion resistance.

    I sure do favor tough-as-nails for outdoors as any home install of mine is necessarily temporary. Seems the best first requirement.

    .
     
    #26 Slowmover, Feb 26, 2021
    Last edited: Feb 26, 2021
  12. dave457

    dave457 Sr. Member

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    They are plenty of other threads in this forum on this subject... Use the search and make-up your own mind
     
    Unit 194 likes this.
  13. L2

    L2 Well-Known Member

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    My Times Microwave LMR400 is up over ten years now. I'll replace it with the same when the time comes.
     
    freecell and Ranch55 like this.
  14. M0GVZ

    M0GVZ Sr. Member

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    For CB radio unless you're running a ridiculously long feedline or stupid power more than a few hundred watts it doesn't really matter a toss what you use as you'll struggle to notice the difference on the S meter between RG58 and LMR 400 for a typical run in a home installation and in a mobile installation anything above RG58 is just throwing money away. Hell even for amateur radio on the HF bands it's throwing money away if you're not running QRO or high SWR and I say that as a contester.

    The difference in a typical home install where your feedline run is hoing to be under 100ft between those two is fractions of a S point.

    I made the silly mistake of buying into the whole "must have best coax" rubbish myself early on and upgraded a perfectly decent 120ft run of RG213 to Ultraflex 10 which had half the loss. Do you know what I noticed? The Ultraflex was nicer to work with and it could be bent much easier round corners but on the S meter it made absolutely no difference.
     
    #29 M0GVZ, Feb 27, 2021
    Last edited: Feb 27, 2021
    HomerBB likes this.
  15. M0GVZ

    M0GVZ Sr. Member

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    I doubt you'd notice it on the S meter as it's not even half a S point.
     

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