Hans, the VF of coax or any cable is greatly depends on what is in contact
with the skin of the conductor. Air, semi air, foam, solid dielectrics, will
each will have a different effect on the skin.
73 & DX,
Gary - AB9M
-----Original Message-----
From: Hans Hammarquist via TowerTalk
Sent: Wednesday, October 08, 2014 12:19 PM
To: towertalk@contesting.com
Subject: [TowerTalk] velocity factor?
Dear Ham Friends,
Recently I checked my feed lines to my tower. I have 1" hardlines, each 88
feet long. I checked the loss by measuring the SWR at various frequencies.
(~0.8dB @150MHz)
I decided to also check the velocity factor. I was a little puzzled to get a
factor of 0.8. Does that make sense? It's a foam filled coax. I expected
something around 0.9.
My resonances were 2.2, 6.767, 11.228, 15.673, 19.945, 24.335, resp. 28.53
MHz indication an electric 1/4 length of 33.73 meter or 110.67 feet.
88/110.67=0.795.
Any comments? Did I do anything wrong? The coax were open in the other end.
Does that give me the wrong value?
73 de,
Hans - N2JFS
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