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Re: [RFI] Fan Noise on Repeater

To: "Jim Brown" <jim@audiosystemsgroup.com>, <rfi@contesting.com>
Subject: Re: [RFI] Fan Noise on Repeater
From: "Tom Rauch" <w8ji@contesting.com>
Reply-to: Tom Rauch <w8ji@contesting.com>
Date: Tue, 9 May 2006 09:01:04 -0400
List-post: <mailto:rfi@contesting.com>
> These are questions for YOU to think about -- they focus 
> on the
> possible mechanisms whereby the noise could be getting 
> into your
> system. It could be RF, coupling into the antenna or 
> feedline, or it
> could be baseband noise coupling into the repeater through 
> its audio
> and power supply circuitry. It could be the fan generating 
> the
> noise, its power supply, or its controller.

Most common and forgotten is the noise is most often caused 
by the fan shaking something that is loose.

A loose connector, a loose connection, a pressure fit 
connection, a bad metal to metal contact on a cover, case, 
or cabinet, and so on. The fan could also be shaking an 
inductor and phase modulating the rig.

It very rarely is an actual RF noise generated by the fan. 
ESPECIALLY in a repeater.

The repeater, if constructed properly, should be VERY immune 
to RF sources from around the equipment. The RF input system 
in particular has to be very well shielded.

Although possible, it is actually unlikely to actually be RF 
radiation from the fan.

73 Tom 

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