----- Original Message -----
From: "Jim Brown" <jim@audiosystemsgroup.com>
To: <topband@contesting.com>
Sent: Tuesday, April 29, 2014 2:28 PM
Subject: Re: Topband: 1000 feet 5/8" hardline or 600ohm True Ladder line.
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
1/2" CATV hardline is about .085 dB/100' at 2 MHz and increasing to a hair
under .4dB at 30 MHz.
The 3/4" chart is well below .1 dB at 2 mHz and doesnt show on the chart
until 5MHz at .11dB/100' and .26dB at 30 MHz.
Carl
KM1H
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