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Re: [RFI] RFI from Apple Airport Extreme

To: "Christopher E. Brown" <cbrown@woods.net>
Subject: Re: [RFI] RFI from Apple Airport Extreme
From: "doc@kd4e.com" <doc@kd4e.com>
Reply-to: doc@kd4e.com
Date: Thu, 30 Dec 2010 18:11:38 -0500
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
Different suggestion ... replace the noisy wall-warts with
analog ac-dc power supplies.

> I have 3 Airport Extremes, 2 of the second gen (2.4 or 5 Ghz,
> 10/100Mbit ether, draft 802.11n) and 1 of the newest (2.4 and 5 Ghz,
> 10/100/1000 ether, 802.11n).
> All three use the same power supply, and all three supplies are
> noisy, dumping common mode noise out both the AC and device sides.
> Noise is classic switcher hash, repeating all the way up past 10m.
> On 2 of the 3 I have a 2.4in type 31 toroid with 10turns on the AC
> side (max turns I could fit with a neat winding), and 14turns on
> another toroid on the output to the AP.
> This is enough to silence them on 40M and up, on 80M I can still
> detect, but only when band is totally closed, normal noise floor band
> open covers them.
> The third is closer to the antenna (35 feet instead of 60ish for the
> other 2), and the AC power feed is in a much better position to act
> as an antenna.  This one has 2 toroids on each side of the PS, and
> 14turns through a toroid on the ethernet cable leaving the unit.
> Some folks plug these in and never have an issue, depends on the
> cabling they connect to.  I happen to have a small space, with the
> antenna ~ 35 feet from the rear wall of the house, and AC wireing in
> a great position to play antenna.
> I would suggest starting by choking both AC and device sides of the
> PS, and the ethernet run to the broadband unit where it leaves the
> airport.


A blessed New Year & 73, doc, KD4E
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