buying an oscilloscope

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David,

I agree with whomever wrote about sticking with Tek analog scopes. If you
want your squarewaves to look square though you need a bandwidth 10 times
the signal of interest ( i.e. 20 MHz squarewave 200 MHz scope ). The more
odd harmonics you can push through the more " square " it will be, and you
would like to pass the 3rd, 5th, 7th and 9th harmonics if possible. I still
like my OLD Tek ( 5000 BTU, Ethan could use this in the South Pole ) 535A
with CA plug-in for most old vintage stuff. The display is still as crisp
and bright as the day I bought it ( used at a salvage sale ). I have a high
dollar Tek digital LCD scope but was very disappointed to find out the 2 GS
/ second front end is only 8 bits wide !!  I only use it if I need a
hardcopy for a customer of some signal or to capture a signal that only
happens once. The signal displayed is only as " crisp " as the dots in the
LCD are small. Good luck in your search. Now, if you could find an HP
LogicDart cheap somewhere ......?

Best regards, Steven



> Gerhard wrote about a 100 MHz oscilliscope:
> >    For slow signals usually present in classical hardware, thats no
> > problem.
>
> That's true.
>
> Many people have the mistaken belief that a 'scope with 20 MHz bandwidth
> is adequate for looking at 20 MHz digital signals, but that is not true.
> For digital signals you usually want bandwidth of at least five times the
> peak frequency of the system, and preferably more.  It's hard to
> diagnose problems when fairly square edges on signals look like
> sine waves on the 'scope.
>
> Eric