On 8/8/2012 2:13 PM, Mel Crichton wrote:
> Any help out there? The warranty isn't expired yet, but I will be removing
> screws in the next few days. I may get lucky with some simple shielding
> (Already wrapped the AC cord in ferrites)
What do you mean "wrapped the AC cord?" Do you mean that you clamped a
bunch of them onto the AC cord, or that you wound multiple turns of the
cord through a big ferrite core? The former is unlikely to solve
anything. The latter COULD make a big dent in the part of the noise that
is conducted onto the AC cable. Study my RFI tutorial for detailed
recommendations.
http://audiosystemsgroup.com/RFI-Ham.pdf
Another important thing to check is where the green wire in the power
cord goes inside box. Make sure that it goes directly to the metal
chassis, and that paint is not interfering with that connection. Also
make sure that tall metal parts of the body and chassis are making good
contact with each other, including the paint issue.
The trash is very likely to be generated by a variable speed motor,
which is essentially DC chopped into pulses of varying width. If the
layout of that wiring is poor it becomes an efficient antenna and also
generates a strong magnetic field. Good shielding can confine this
shield inside the box, but poor shielding will result in a lot of noise.
It could be a MAJOR project to fix the part of the problem generated by
internal wiring.
Frankly, I think you're making a HUGE mistake by waiting until it's out
of warranty. I would INSIST, VERY LOUDLY, and VERY PUBLICLY, that they
fix it as a defective product. It is defective because, according to
Part 15, any customer MUST cease operating it if it interferes with
licensed radio communications.
If you don't do this, you've just gotten screwed out of whatever you
paid for it. And the only way this stuff gets changed is when customers
make it sufficiently unpleasant or unprofitable for the company. When
we run into problems like this we owe it to our fellow hams to take
serious action. As we learned years ago in the civil rights movement,
if you're not part of the solution, you're part of the problem.
73, Jim K9YC
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