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Re: [RFI] Noisey PSU (Laptop) on HF Decodeing

To: k0occ@comcast.net, RFI@contesting.com
Subject: Re: [RFI] Noisey PSU (Laptop) on HF Decodeing
From: Fred Stevens K2FRD <k2frd@mac.com>
Date: Tue, 29 May 2007 19:49:44 -0700
List-post: <mailto:rfi@contesting.com>
I absolutely agree that it is seldom a simple issue with RFI. It also occurs to 
me that my newest Mac which causes the most RFI is also equipped with a 
wireless card meaning it also has an antenna (located around the perimeter of 
the lid) which then makes radiation of any RFI which comes into the laptop that 
much more pervasive (all three laptops are located within 6" to 18" of my 
TS-2000 - any computer-generated RFI is almost a hardwired feed). The other 
two, older laptops are not so wi-fi antenna equipped. The old Dell is perfect 
for digital as long as I keep it on battery instead of commercial power (to 
which I have been connected only once in four years as a fulltime RVer; I'm 
usually on generator or solar power, but that's yet another issue: boondocking 
RVs and RFI).

73 de Fred K2FRD

At 8:36 PM -0400 29/5/07, Tom Rauch wrote:
>But of course we all know it takes two to tango!!!
>Not only must the PS make noise, the noise must somehow get into the receiving 
>Every fast efficient switching supply in the world makes noise, but how much 
>it bothers our stations depends on our antennas as much as it does the supply. 
>It depends on how the feedlines are decoupled for common mode, how far the 
>antennas are away, the local noise level, the receiver bandwidth we use, 
>ambient noise levels around the site, and many other things.
>Unless you can refer each PS to a uniform measurement standard of coupled 
>noise into the power mains, what works in one place is largely meaningless 
>somewhere else.
>A big problem when using computers for interfaces with radios is you are just 
>begging for setting up common mode ground loops that aggravate the whole 
>thing, especially when a station has a poor wiring layout for ground loops and 
>common mode on antenna feedlines.
>It is just as important to describe the antenna as it is the computer.
>73 Tom

73 de Fred Stevens K2FRD, VO2FS
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