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Re: Topband: 1000 feet 5/8" hardline or 600ohm True Ladder line.

To: topband@contesting.com
Subject: Re: Topband: 1000 feet 5/8" hardline or 600ohm True Ladder line.
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Tue, 29 Apr 2014 11:28:42 -0700
List-post: <topband@contesting.com">mailto:topband@contesting.com>
On 4/29/2014 10:08 AM, Richard (Rick) Karlquist wrote:
The ARRL Antenna Handbook shows about 0.4 dB for 420
feet of 75 ohm 1/2 inch hardline.

I suspect they are talking about 75 ohm heliax, not the typical CATV hard line. The CATV hard line I've seen has an Al shield, so I would expect loss to be a bit greater than heliax, which has a much heavier copper shield.

Paralleling two
runs of line does not decrease the insertion loss.

That depends. Given the same source and load Z as with the single run, it does decrease the loss, because the current divides between the two lines. The condition that does not reduce the loss is the use of two runs of coax wired in series to raise their impedance, so that the center conductors are parallel wire line.

73, Jim K9YC


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