Topband: 160m noise

[BobK8IA at aol.com]

In a message dated 11/9/04 5:16:40 AM US Mountain Standard Time, 
btippett at alum.mit.edu writes:
To make a long story short, the problem was a switching power 
supply in
a new white box computer 
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I just recently had a similar experience with two present day computer power 
supplies, both of "Made in China" variety. It wasnt just birdies on 160 but 
actual "hash": that occupied approx 50 khz bandwidth and the center of that hash 
moved from about 1790 to about 1815khz, depending on how long the computer 
was operational. Until I recently erected a pair of K9AY loops, the noise was 
not even evident on my normal 160m antennas, a Inv V and an In L. No other 
significant noises on any other band, btw. 

I found the source by pure desperation. After unsuccessfully investigating 
other possible sources here at home, I powered down the desktop computer that 
runs all my ham stuff and, voila, the noise disappeared, dead quiet! What is 
interesting is that I have 3 other computers here in my hamshack/office that are 
dead quiet. One of them, that runs my business software etc, is a 6 yr old 
Gateway P3-450, across the room,  that has only been turned off maybe 4 times in 
its entire life. The other two are laptops, one a very new IBM P4-2100 Think 
Pad, also across the room, and the other a 8 yr old Compaq P2-240 laptop that 
sits right at the operating desk as my ham backup. Agn, all these are dead 
quiet. The culprit computer is one I assembled from a "kit". Humm.....

Anyhow, I had a spare power supply, also of the "Made in China" variety. I 
swapped this out with the "noisy" one and guess what? This one was even noisier. 
What a racket and all over the spectrum. 

This all happened this past wekend, so my next task is to research some of 
the EMI products that can attenuate this headache. I see that Corcom and others 
have slick "entry modules", essentially an AC receptacle with a filter 
enclosed, to replace the one on the power supply. These are gernerally cost effective 
from what I quickly saw in a Google search. A quieter supply would be a 
solution as well, of course. The W3NQN AC Filter looks inviting, but, frankly, not 
at $100. 

Any suggestions?


73, Bob K8IA