Guy,
No, I don't have a clue what it might be. It's kind of like asking "I've got a
set of four black tires with white sidewalls on one side of them. Will they
work on my car?"
But you can test the coax and get a rough idea about the impedance by putting a
50 ~ 52 Ohm resister at the far end and measuring the VSWR. If it's 1:1 that
would tell you it's a 50 Ohm impedance. If it's 1.5:1 that would suggest a 75
Ohm impedance. Or you could put a 100 Ohm potentiometer at the far end and
adjust it for minimum VSWR, remove the pot, and measure its resistance. That
will be the approximate impedance of the cable.
If you have (or can borrow) an antenna analyzer (MFJ259), you can short the far
end and measure the lowest frequency of the VSWR dip. Then you can calculate
the velocity factor by measuring the physical length compared to the free-space
(calculated) length. This will give you the ratio between the two (i.e., the
velocity factor).
With a couple basic tools, you should be able to determine what you need to
know. It's a good problem to have that will teach you about RF and some basic
measurements. You can Google "measuring unknown cable impedance" and find more
specific details.
73 de Bob - KØRC in MN
Message: 4
Date: Tue, 2 Nov 2010 06:15:28 +0000
From: Guy Molinari<guy_molinari@hotmail.com>
Subject: [TowerTalk] Mystery hardline
To:<towertalk@contesting.com>
Message-ID:<BAY129-W16905245A9B5BD0978CBAE8490@phx.gbl>
Content-Type: text/plain; charset="iso-8859-1"
I picked up some surplus hardline. It has an OD of 5/8" including a 1/16"
plastic jacket. The jacket is black and has a green stipe running up 2 sides
of the cable.
Any idea of what this stuff is? Specs?
73,
Guy, N7ZG
------------------------------
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