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[TowerTalk] isolation and SWR

To: TowerTalk <>
Subject: [TowerTalk] isolation and SWR
From: Pete Smith N4ZR <>
Date: Mon, 10 Sep 2012 11:03:04 -0400
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Just now, I was fiddling with my homebrew 80m array switchbox. I have only two dipoles on it at the moment, both reasonably well matched. Accidentally I switched to one of the unterminated positions, and got an SWR on the order of 4.5:1 (feeding the dipole switchbox through my Ameritron RCS-10. By comparison, if I disconnect the feedline inside the shack, the SWR is in excess of 25:1, and if I switch the RCS-10 to an unused position, I get 4.5:1.

Is there even an approximate relationship between these various SWR numbers and the degree of isolation afforded by the two switchboxes? And probably an even dumber question. If you have two devices in line and each has (say) 30 dB isolation between a line in use and an unused one, both of which pass through them both, is the resulting isolation 27 Db? Some other number?

Be gentle - I was a liberal arts major.

73, Pete N4ZR
The World Contest Station Database, at
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