[Elecraft] Computer Noise ruining 20 & 30m

[Ed Gray W0SD]

I realize this is not a specific Elecraft topic but it is in response to 
a request and it is on a radio subject.  It would be interesting on 
reports on what the K3 noise blankers do on this type of noise.

First of all I am no engineer but I have had some experience with this 
problem.

I got the top of the line Carcom line filter based on suggestions on the 
160 reflector and installed it right to the PC with about 1 inch of line 
cord and I put ferrite on that 1 inch.  I knocked the noise down a 
bunch,  I have to do some testing on a dead band to see if it is all 
gone but it made a huge improvement.  I have to suspect your AC line 
filter is not a very good one OR the case is leaking.  I say this 
because using the AC line filter seems to be the common cure that works. 
  Fortunately my case was metal but on a lot of the new computers there 
is a lot of the case that is plastic.   For me the problem was the worst 
on 160 meters.  From my tests the noise was coming in over the antenna

I was going to switch computer power supplies but my old ones did not 
provide the extra voltage line that most of the newer supplies do and 
that my mother board required.  If I remember correctly the extra line 
had to do with the dual processor.  It is kind of a catch 22 as the 
newer supplies that plug into the newer computers just are not built 
like they were for filtering.  I am hoping someone can suggest a power 
supply that work with the newer computers that can be bought from places 
like Tiger direct etc. that is well built and quiet.  One hates to buy a 
new supply and have the same problem and from what I can tell the odds 
of that happening are pretty high..  One could try and determine the 
noise level on a broadcast receiver and then go to a friendly computer 
shop and try some supplies until you found a quiet one on the broadcast 
receiver.  That might not be all that cheap if you have to try several 
and take up a lot of time.  It seems to me buying one that is of good 
design that others have not had problems with would make the most sense 
if one knew which one to buy. .  Another approach is if someone would 
buy a supply and fix it and then document what supply it was and how 
they fixed it with filtering and toroids it would be a great service as 
this problem is going to be  become very common as us hams update our 
computers.  Actually I suspect they are all built about the same so what 
worked on one would work on all of them.  A good article for one of the 
ham magazine but for now it could be on a web site.

I will be interested in what others say.

Another common problem is birdies from the Router and CAT5E cable.  I am 
digging into that,  here they seem to be on all the bands spread out.  
One can work around them but I want to get rid of them.  Toroids seem to 
be one answer as a lot of routers have this problem.  Again if someone 
knows of a router that is clean that would be an easier fix as some of 
the big toroids are not cheap.  I guess one could buy various routers 
and take them back within the 30 day return period until you found a 
clean one but it sure would save a lot of hams a lot of trouble to know 
of one that is clean.  I would be interested in what others say on this 
subject.

Thanks

Ed W0SD


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