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

To: topband@contesting.com
Subject: Re: Topband: 1000 feet 5/8" hardline or 600ohm True Ladder lin
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Tue, 29 Apr 2014 09:22:03 -0700
List-post: <topband@contesting.com">mailto:topband@contesting.com>
On 4/29/2014 8:00 AM, Kenneth Silverman wrote:
We lost the data but I seem to remember the total loss on 80/160 with 1000' of 
line was negligible.  Maybe in the 2 dB range on 10m with 1000' of ladder line.

I suspect few here would consider 2dB negligible. i don't. N6BT says 2dB is a lot.

On 4/29/2014 8:32 AM, Shoppa, Tim wrote:
Really, for decades I did not understand why ladder line had so much less loss 
than comparable-copper coax.

It's because ladder line is used at 450 or 600 ohm impedance, so it of course 
has one tenth the resistive losses of 50 ohm coax built with similar amount of 
copper.

Exactly right -- it's because the current is much smaller for the same power.

On 4/29/2014 8:49 AM, Milt -- N5IA wrote:
For my 160 Meter, 1/4 WL vertical, which is more than 400 feet from my operating position, I use 1/2" CATV hardline X 2.

Since the feed point impedance of the vertical measures ~ 39 Ohms, I parallel two of the 75 Ohm cables for a near perfect match to the antenna.

The 420 foot long run of paralleled cables dampens the slight mismatch between the presented impedance of 37.5 Ohms and the desired 50 Ohms for the amplifier such that the Alpha does not light a single reflected power segment from 1.800 to 1.880.

Exactlly right again.

Many of the "best" solutions for antenna problems depend on which of them are readily available to us. If you have that CATV hard line, it's a great solution once you know how to use it.

Another great way to use 75 ohm cable in a 50 ohm system is to use some multiple of half waves of it, coiling up any excess, or using 50 ohm coax to add length.

None of these solutions are "new" or particularly innovative. All have been used since the earliest days of radio.

73, Jim K9YC
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