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Author Topic: Coax  (Read 678 times)
KE4IZA
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Posts: 240




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« on: January 24, 2003, 09:11:32 PM »


    I just bought the Icom IC-718.  It will be connected to an MFJ-949E tuner.  I want to know what kind of cable should I use for my antenna feed line?
I see RJ-58, RJ-8U, RJ-8M.

Thanks guys!

Jim Glenn
KE4IZA
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WB2WIK
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Posts: 20559




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« Reply #1 on: January 27, 2003, 12:08:11 PM »

Coaxial cable prefixes are "RG" not "RJ."

RG58 type is very small diameter (.195"), has considerable loss, limited power handling ability, low dielectric breakdown voltage rating, and is mechanically quite weak.  I can hold a 2' length in my bare hands and snap it quickly, and break it in half.  Not my idea of a long-lasting transmission line.  Perfect for temporary installations, short indoor runs, "patch" and "jumper" cables where high power will never be used, stuff like that.

RG8"M" is the same as RG8"X" and is commonly called "mini-8."  It's .242" diameter and a tad stronger than RG58, and has considerably less loss; however it's still mechanically fragile and will only handle high power if perfectly matched.  I use it for similar applications to RG58 types, and never for a permanent, outdoor transmission line.

RG213/U is .405" diameter and much stronger.  You can walk on it, and probably even drive over it, without damaging the cable -- and that can be important in many installations.  It will handle high power, and high voltage (important for mismatch applications), and lasts a long time.  Most recommended for "permanent" installations outdoors, and only costs pennies more per foot than RG8X.  This is pretty much the "minimum" coax I'll ever use outdoors, except temporarily.

WB2WIK/6
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