SV: Re: SV: Re: [sdiy] ARGHHH - PIC detunes VCOs depending onRFI *only* if USB cable plugged in

[harrybissell]

AMEN !

(note, ascii text. please read the above in the 72pt. font of your
choice...
bold, underlined :^)

I have hybrid digital scopes. They can have the digital mode turned off
at will.

I remember a young tech working on an A/D problem. He announced he had
"found the problem"... noise from the switching power supply. I said
"show me"... and he did. HUGE noise spike every five divisions.

 I asked him what the frequency was (he did not know how to calculate
that...
1/period ). Switching noise should be related to the switching
frequency, na ?

When I moved the timebase... the noise stayed at five divisions
(impossible)
Switched to analog mode, the noise was wideband and the 'spike' as an
aliasing
artifact.

Sadly, the tech's education came to a sudden halt when he tried to take
a trunkful
of equipment across the Canadian border. When caught, he said "my
employer TOLD me
to just sneak it across...."   (not true).   If he had played dume they
might have
hassled and forgiven him...   :^P

H^) harry  (going to Canada tomorrow, NOT taking anything !!!)



Eric Brombaugh wrote:
> 
> And on top of that, be very cautious about digital 'scopes. Aliasing,
> undersampling, display modes, etc can all wreak havoc on your
> measurements. Analog 'scopes may not be as snazzy, but they are a lot
> friendlier.
> 
> Eric
> 
> harrybissell wrote:
> > Karl Ekdahl wrote:
> >
> >
> >> Unfortunley i don't have a HF oscilloscope (this is
> >> where my soundcard-scope is biting me in the ass) so i
> >> can't see any >44khz interference...
> >>
> >
> > Yeah. I consider PC cards "data acquisition"  and not
> > "instrumentation"... I never trust "DA" unless it agrees
> > with an independant authority (scope)
> >
> > H^) harry
> >
> >