[TowerTalk] Coax Loss -- RG-Numbers Don't Tell us Much

[Michael Goins]

Good information, but I need some suggestions.

I will have a run of about 100 feet station to to the tower and then
up 75 or so feet. I operate at 1 watt much of the time and need
suggestions regarding coax and some possibility of economy. Will be
feeding a 2-el quad via a remote switch, and will also be feeding
(independently, seperate runs) a gain vertical for 2 meters and also a
commercial vertical for 30/40.

What would be relatively cost-effective? Does 75 ohm cable end make
sense? LMR? I do have to cross a road (on our property) so it will
likely run overhead (the ground is rock - all rock).

Michael Goins, k5wmg
Pipe Creek, Texas
former editor, qrp quarterly
Fast cars, slow boats, big dogs, and summers off to write




On Thu, Feb 4, 2010 at 3:03 PM, Rick Karlquist <richard at karlquist.com> wrote:
> Jim Brown wrote:
>> On Thu, 4 Feb 2010 10:38:19 -0800, Rick Karlquist wrote:
>>
>> Rick,
>>
>> My point is that virtually all transmission line losses at HF are I
>> squared R
>
> That is not in dispute, but what is in dispute is the
> assumed proportionality of R to the square root of frequency.
> A copper plated aluminum cable that is better than an all
> copper cable at 50 MHz may not be better at 1.8 MHz.
> But the DC resistances will be yet another set of numbers.
> Hard to generalize.
>
> Look at some examples in the Belden catalog:
>
> 7977A and 8214 have the same DC resistance but 2:1 RF loss ratio
> 8237 and 7809 have the same RF loss but 1.5:1 DC resistance ratio
> (RF loss at 50 MHz).
>
> Rick N6RK
>
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