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Ladder line Vs. Coax
Sonny Hood wrote in
: I have an efficiency question concerning feed lines. My present system is RG-8X to my 75 meter inverted vee which is about 85 feet away from the shack. I propose to replace some 88 feet of coax with 300 ohm window ladder line that is inserted into the coax run with 4:1 baluns to match the coax on each end. Also at the feed point of the antenna switch from a voltage balun to a current balun (ferrite chock type). By my calculations with a 98 watt generator I will increase the power to the load by about 11-20 watts and with a 985 watt generator, 117-210 more watts will reach the load. Figuring theoretical total system (A) against total System (B) or by just the difference in the 88 feet of ladder line versus coax. What do you think the increase will be? One of the numbers that is hard to come up with is the loss through a balun. The only number I could find for a voltage balun is a matched loss of 0.075db, this would be times 2 in your setup. So there is loss, and it's well known that the loss goes up with miss match. I think you are neglecting the loss through the baluns and the miss match loss. Remember your antenna will not be 50 ohms over a very wide frequency range. Going open wire line all the way or changing to RG8 size coax will likely work just as well and be simpler to do. John W3JXP |
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