[sdiy] Poor man's EMC testing?

[cheater cheater]

On Sat, Mar 20, 2010 at 00:09, Barry Klein <Barry.L.Klein at wdc.com> wrote:
> Am I wrong or am I sensing a bit of email hostility in this topic?
> I don't really understand it, and maybe fingers are pointing at what I
> suggested and I just don't get it..
>
> My suggestions were pointed at someone with the inability to borrow/use a
> spectrum analyzer or perhaps not knowing that one can be had for under a
> grand.
>
> While my management hum hawwed about getting our group a spectrum analyzer
> I got the sniffer probe set and preamp and used it with my LeCroy.  True, my
> LeCroy was probably a 30 grand scope in its day, but now is likely an under
> 1 grand scope.  It worked fine for finding fundamental freq. issues - those
> under the 330Mhz that someone mentioned.  Knock down the fundamental the
> harmonics usually follow.  Thing is if you have never done this sort of work
> you are on your own doing DIY experiments, reading a ton about it on the
> net, and just continually trying things to reduce the emissions.  Components
> used, layout, pc grounding, enclosure grounding, bypassing, clock series and
> termination resistors... all comes into play.  EMI tape helps but
> management usually hates it.
>
> Now if you don't have a scope even capable of the FFT mode and you still
> want to do something... but not pay someone, and not buy a spectrum analyzer
> but maybe find critical areas try making a sniffer probe off what you'll
> find on a google search and build a preamp like I did using a mini-circuits
> amplifier, feed it in to your scope and just probe around looking for signal
> sources.  Some will make sense and others may surprise you.  Try fixes
> mentioned above and maybe you'll have less test time at the "real" lab.

So if I understand correctly, that + maybe a band-limiter + frequency
shifter could be enough to jury-rig something to help find *some*
problems? That takes us far away from the world of scientific
measurement, since we can't actually tell the magnitude of the
measurement, but it can give us some idea - right?

--------

Magnus and Grant:
what set me off was the form, not the content. I did not appreciate
the information conveyed in such manner just like I wouldn't eat a
good dinner off a toilet seat. I'm sure you'll find others who have
similar ways of thinking. We were always taught at university that
hostility makes it impossible for students to learn what we want to
teach them.

I guess you can call me a monster for not liking to be mocked or
looked down upon, but whether someone wants to see me this way is
everyone's personal choice.

Best regards
D.