Hello, Van--
Keep in mind that the SWR meter is designed to operate with a given
impedance--almost certainly 50 ohms; it will produce erroneous readings when
connected to other impedances (input or output). In other words, you can't
trust the meter readings you obtained; they almost assuredly are incorrect.
Further, even if you could trust the meter, there will be an impedance
transformation caused by the 70 ohm line. I now have to bow to those more
knowledgeable to provide details about that, but I would not expect radical
SWRs to result if those feedlines and the connections are good. My guess is
that the 2:1 readings are more a result of the fact that the meter is
designed for 50 ohms.
Good luck--it'll be interesting to see how this plays out.
vy 73
Jim, W3WV
________________________________
Jim Wilcox
----- Original Message -----
From: "Van Fair" <vfair@innova.net>
To: <towertalk@contesting.com>
Sent: Tuesday, 14 October, 2003 21:46
Subject: [TowerTalk] Question concerning Hard Line
A friend has 60 to 70 feet of hard line (type unknown) buried to his tower
and then RG8 up the tower. On the transmitter end it has 10 feet of RG8
before the hard-line.
He is having a problem with high SWR on his beam. In checking it out I put a
52 ohm dummy load at the end of the hard line at the base of the tower and
found a 1-1 SWR at 12.53, 20.71 and 16.63 MHZ. Over the rest of the freq the
SWR was much higher including 2-1 at 14.2, 1.9-1 at 21.3 and 1.5 -1 at 28.6
MHZ. This seems abnormal and my experience says it should be close to 1-1
on all freq. but I have only used 52 ohm coax. The hard-line may be 72 - 75
ohms. Would this cause the above type of readings or does this indicate some
other problem.? It seems to me that mixing hardline and coax of different
impedance is not good but does it work?? Thanks Van
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
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http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
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