On 2/4/10 13:30 , matt weber wrote:
On Wed, 3 Feb 2010 16:21:54 -0600,
wrote:

I'm running a 6v 300ma adapter to run my Sangean ATS800 radio. I was
wondering if applying a couple of ferrite chocks like this to the DC power
cord would eliminate any humming noise created by the adapter.

http://www.piurl.com/p/22mW


The humm is not very loud, but it's noticeable. I know batteries are the
best solution, but in this case it's more convenient to use the adapter.


I doubt it. The ferrite cores act as the core of a choke. If the AC
adapter used a switching supply, perhaps, but most wall warts are very
simple linear supplies (keeps the cost down0, so the hum is at 60Hz.
You are going to need a lot more inductance than a couple of ferrite
cores to keep it out.

That depends on whether the hum is simple ripple, or if it's an
artifact of rf mix products from local sources coming in on the DC
line from the adaptor. That's actually fairly common if there's a
local radio source. This type of hum may be distinguished from
simple ripple by the fact that it shows up at odd places across the
dial, and changes as the DC cord is moved. It shows up on stronger
stations than weaker, and generally isn't present during
interstation noise.

Usually, cores at the wall wart and cores at the DC connector
will, for all intents and purposes, eliminate this type of hum. In
sever cases, other types of filtration and a grounded wall wart will
be necessary.