[Elecraft] OT: Maytag Bravos RFI

W0SD Ed Gray w0sd at triotel.net
Thu Sep 24 12:51:44 EDT 2009


I would consider this a whole lot less OT than a lot of things I read. 
I found it very valuable. There seems to be a site for nearly everything 
on the internet anymore.  A valuable site would be one that hams would 
participate in and list items that are clean and don't interfere with 
the radio spectrum.  The switching supplies seem to be a major culprit 
and it is just going to get worse.  Even those that meet the FCC Part 15 
Class B standards can be a real problem with our amateur equipment.  In 
roughly the last year I have had switching power supply noise from my 
new computer which made DXing on the low bands impossible until I solved 
with filtering on the AC line.  I had router noise across all the bands 
which made many, many frequenies un-useable some of which were places I 
operate a lot which I could not anymore.  Fortunately I pretty well 
cured this by slowing the speed. Both of those answers came from this 
reflector so I would not call help permitting me to use my K3's OT. My 
latest problem which I have not been able to solve is 24 khz switching 
noise from my Outback MPPT solar controller.  The harmonics from it make 
it all the way up to two meters. It is S-9+15 db on 160M.

This switching noise is a tough one as IMHO it should be cured at the 
source rather than the output where instead of stopping the switching 
frequency you have the whole spectrum of interference to deal with.  Of 
course if you start modifying internally you are going to void the warranty.

At this point based on my last years experience before I buy anything 
different I am going to do my very best to try and find out about radio 
noise and if I can not then be sure I can return it without a penalty. 
Where possible one may have to bring a K3 with a gel battery to the 
store and check things out. The thing is there are a lot of things now 
that are noise sources that I for one would not expect as almost 
everything is going to switching supplies.

Ed W0SD


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