Re: Twisted Pair Wiring and RFI Rejection
Posted by
Jim Brown-10 on
Aug 31, 2010; 4:50pm
URL: http://elecraft.85.s1.nabble.com/Twisted-Pair-Wiring-and-RFI-Rejection-tp5481570p5483536.html
On Mon, 30 Aug 2010 23:08:34 -0800, Edward R. Cole wrote:
>I believe Cat-5e is isolated up to 100-KHz.
In essence, the ability of twisted pair to reject HF noise is directly
related to the number of twists per inch, and the uniformity of the
twist. The close spacing of the twist also helps. High quality twisted
pair like any of the CAT5/6/7 cables continues to reject noise well into
the VHF range, although the degree of rejection degrades with increasing
frequency. Noise rejection is also a function of the balance of the
receiver, and to some extent, the balance of the output stage that
drives the line.
CAT5/6/7 cables as a group are constant impedance (100 ohms) and have
relatively good bandwidth (well into the tens of MHz). Like any
transmission line, loss increases with frequency.
73, Jim K9YC
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