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Re: [RFI] Common Mode Noise?

To: rfi@contesting.com
Subject: Re: [RFI] Common Mode Noise?
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Wed, 22 Jan 2025 11:09:00 -0800
List-post: <mailto:rfi@contesting.com>
On 1/22/2025 10:43 AM, K9MA wrote:
The whole point of using coax is to prevent radiation until the RF gets to the antenna. There's no need to further complicate the issue.

There is no more or less radiation from a 2-wire line than from coax. What causes radiation is common mode current, and 2-wire can carry just as much common mode as coax of the total antenna system is unbalanced. Just as in coax, common mode current in 2-wire line shows up as a difference between current in the two wires, taking both magnitude and phase into account.

Antennas can be unbalanced by their surroundings, like variable height, sloping ground, nearby conductive objects, imbalance in the termination of 2-wire line in the shack, including a poorly balanced tuner or matching network.

73, Jim K9YC

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