> ANY scope is better than no scope.

> but if you don't have any scope at all, and have no money, a really cheap
> used student model from 1960 will be a great addition to your lab, and
won't
> set you back much more than a week's worth of  big macs.


I agree with the above

BUT !!!

There really is a minimum level below which you have to work hard to make
your tool help you.
The really cheap 60's model student type instruments (eg some bottom end
Heathkit scopes etc) didn't have a triggered sweep that understood the
meaning of the word trigger, had no time base calibration, no vertical
amplitude calibration and more (or, rather, less).

While such scopes DO have a useful place when there is absolutely nothing
else you really really really should try and rise above this level if you
can. I would venture to suggest that an old valve scope with a decent
timebase and y amplifier with calibration would be more useful than a newer
bottom end largely solid state scope. (I've used both). I suspect you could
often do this for only tens of dollars in the US.

As noted before - more is always better but useful entry level is one
beam/trace, proper triggered sweep, calibrated sweep speeds, multi range
calibrated voltage input, 5 MHz bandwidth. After that a second trace is
pretty useful, more bandwidth is always nice, various sync modes, beam
add/subtract etc. Delayed sweep is very useful but usually comes after quite
a jump in other specs. Storage is nice but dearer. Old analog storage scopes
tend to be very dim, very dead, hard to use and cranky. The tube is a very
very major part of the system and they degrade terminally with age and are
cost far more than the scope is worth to replace. (Note that most scopes
have a single beam which is chopped or alternated to make two traces. True
dual beam scopes are rare - the feature is useful to have but only if
everything else meets your spec).

Probably un-useful thought - a modern PC would make an interesting high
speed scope using eg a Sigma Delta A2D if you could burrow under the
operating system and timers etc. You might be able to get many 10's of MHz
of analog bandwidth using a now entry level Celeron/AMD/xxx 850/1000 MHz cpu
and a parallel port.




        Russell McMahon

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