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Old 5-Mar-2011, 5:04 PM   #2
GroundUrMast
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Join Date: Oct 2010
Location: Greater Seattle Area
Posts: 4,773
Those numbers sound right...

Coax is preferred these days because it is able to be mounted directly to metal objects like masts or towers. Coax shielding is excellent at keeping the signal inside separate from the signals and noise outside. With coax, I can drill a 3/8" hole, pass the coax through, caulk it, and I'm on to stapling down the rest of the run.. With paired lines, I could have have dozens of standoffs and through-wall tubes to install.

Unshielded paired wire must be supported every so many inches or feet to keep it from coming close to materials that would affect its' characteristic impedance. Also, unshielded paired line is more prone to act as an unintended antenna, receiving or radiating signals that should not have been. The signal loss per unit length increases more rapidly with increased frequency as well.

Paired lines have their place, look at any of the 2, 4 and 8 bay panel antennas for example; You will see the elements connected to the feed point via paired line. This is to match the impedance of the individual antenna elements with as little loss as possible. As you have already mentioned, HAMs are probably using more ladder line these days than any other single group, given it's power handling and low loss in the HF bands.
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Last edited by GroundUrMast; 5-Mar-2011 at 11:32 PM.
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