Follow up on my RFI hunt info
 

I mentioned my noise probes once before.

A friend wanted real measurements instead of the vague discription.
OK.

My first unit is 29 turns of solid PVC insulated wire on a PM-10 (1
3/8"
diameter) pill bottle with a female BNC mounted in the top.

The next unit is 2 turns inside the same sized pill bottle with a BNC
in the cap.

One nice unexpoected aspect is the ability to use another pill bottle
screwed
on the no child proof cap threads, this makes a handy, but bvery cheap
handold for the probe.

The last one came about because I needed to find the noise source
inside a
linear power supply. This is a ferrite core 100uH in a "Sharpie Fine
Point" with
the coil at the blunt end and a BNC female in the open end where the
colored
plastic insert is force fited..This one is great for sniffing for RFI
at the component
level once the offended equipment is located.

There is nothing special about these coils, they where built with what
I had on
hand. Other values would very likely work as well. A 10Uh might well
have been
a better choice for the last probe, but I didn't have one at hand. I
ight build one
with the 10uH to see if there is any significant difference between the
100u and
the 10uH coils.

I tried Telemons suggestions of a simple stub probe, but found the
coils to
be more effective in my searchs.

I use a DX398 with a 6' 3.5mm to BNC coax.

I have found it useful to start at the fuse/breaker box and turn off
every breaker,
then turn them on one at a time, with the 19uH probe held near each
breaker
as I turn it on I can usually locate the noisest soruce. It may, so far
always has,
take several passes to find every on home noise source.

This simple set of tools allows me to verify that my steps at RFI
reduction are
effective. I have mentioned W1HIS Common mode PDF before, but I must
say
Chuck has gone to a lot of trouble to solve "common mode noise". My
simple
probe is usefull to see if I have knocked the noise down enough.
www.yccc.org/Articles/W1HIS/CommonModeChokesW1HIS2006Apr06.pdf


Terry