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Author Topic: zip wire antenna and feeder line  (Read 7324 times)

AUG4EXAM

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zip wire antenna and feeder line
« on: July 30, 2001, 10:14:03 AM »

I am going to put up a cheap zip wire antenna on my roof, stealth mode, and want to know, why don't I just use the same wire to create an open wire feeder to connect it to my antenna tuner? Antenna is going to be a closed loop, and want to tune it for 40m.

Thanks, Ed
Tech exam on aug 4,  working on code
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WB2WIK

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zip wire antenna and feeder line
« Reply #1 on: July 30, 2001, 11:27:04 AM »

Of course you can.  It's not "open wire," but it is "balanced," and much lower impedance (typically) than open wire or ladder line would be, due to the close conductor spacing.

I've used "zip cord" (lamp cord, typically #18 gauge stranded copper with plastic insulation) lots of time as a transmission line on 40 meters, even on 10 meters, and it's pretty good stuff...around 70 Ohms impedance or so, not much loss -- probably about as good as RG58/U coax on those frequencies.

73 de Steve WB2WIK/6
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AUG4EXAM

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zip wire antenna and feeder line
« Reply #2 on: July 30, 2001, 02:11:42 PM »

I was considering using spreaders in the feed line portion.  Are you suggesting just run it in "un" zipped?  This would have more power loss than if spreaded, right?
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WB2WIK

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zip wire antenna and feeder line
« Reply #3 on: July 30, 2001, 05:48:39 PM »

Yes, I was referring to "unzipped," with the conductors very close and held in place by their original insulation.

On 40m, the difference, if you're feeding a resonant loop, between "unzipped" (70 Ohms) vs. "zipped apart" (450-600 Ohms) should be essentially nothing, because the line loss will be extremely low either way.  However, if you need to feed the 40m loop on other bands where its impedance might swing wildly, e.g., 20m where its impedance can get very high, the "zipped apart" (open wire type) construction will work better.

73 de Steve WB2WIK/6
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AUG4EXAM

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zip wire antenna and feeder line
« Reply #4 on: July 31, 2001, 08:59:58 AM »

Ahh, so if as Tech +, on 15, and 10m I would want spreaders.  Thanks for that insight. Thanks.
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