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Re: [RFI] RFI from Apple Airport Extreme

To: John <jonie41@simcoemail.com>
Subject: Re: [RFI] RFI from Apple Airport Extreme
From: "Christopher E. Brown" <cbrown@woods.net>
Date: Thu, 30 Dec 2010 17:01:05 -0600 (CST)
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
On Wed, 29 Dec 2010, John wrote:

> Hi All,
> Have just installed an Apple Airport Extreme wireless router.
> Works like a champ, very happy with the device.
> Till I turned on the rig...birdies all over 20m!!
> Are any of my fellow hams using the same router without the birdie problem?
> Any alternate recommendations for a dual band wireless N router?
> I must add that I did do a bit of investigation and noticed that when I
> removed the feed from the broadband unit (on the roof, 900MHz transceiver)
> to the Apple unit, the majority of the interference decreased markedly but
> was still there.just.
> Any ideas?
> Thanks and Happy New Year to all...
> John, VE3KKQ

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, 

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 

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.
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