I have been using my Tek T935A (35 Mhz or thereabouts bandwidth) for all of
my design and troubleshooting and have never found it lacking. I have not
yet needed it to analyse a 35 Mhz squarewave where much higher bandwidth
would be needed to analyse waveshape. I have used it a lot on all kinds of
boatanchor and modern digital projects (HF interest only, not VHF) and for
casual use it is all I need.
As an electronics engineer my career included a lot of lab time where high
speed digital circuits required high bandwidth "glitch-catchers" as well as
sophisticated triggering systems and storage capabilities that showed you
what had been happening *before* the triggering. However, my ham radio
interests have never demanded anything more than what I have.
My experience is that reliable and *stable* triggering is just as important
as bandwidth.
Don K7FJ
----- Original Message -----
From: "Tom McCulloch" <[EMAIL PROTECTED]>
To: "Ron D'Eau Claire" <[EMAIL PROTECTED]>; "'Jack Regan'"
<[EMAIL PROTECTED]>; <elecraft@mailman.qth.net>
Sent: Sunday, June 25, 2006 10:40 AM
Subject: Re: [Elecraft] Scopes
I'll follow this thread with interest, as I too am considering a scope
purchase.
I've heard comments such as Ron's before. I'm wondering if anyone has any
thoughts on what bandwidth would be appropriate for "casual" use and what
someone might expect to pay for a use one?
Thanks in advance
Tom
wb2qdg
k2 1103
----------------------------------------------
Teamwork is a lot of people doing what I say.
----- Original Message -----
From: "Ron D'Eau Claire" <[EMAIL PROTECTED]>
To: "'Jack Regan'" <[EMAIL PROTECTED]>; <elecraft@mailman.qth.net>
Sent: Friday, June 23, 2006 8:39 PM
Subject: RE: [Elecraft] Scopes
Jack, A36GC asked:
I am thinking of getting a scope to better build and repair Elecraft
radios.
I have a line on a Tektronix 2336YA 100 MHz 2 Chl. Oscilloscope that is
calibrated! It is about $200. Is this a good deal? Is this a good
scope?
-----------------------------------
Teks are excellent scopes, overall. That's a very low price. The only
caution I'll offer (and probably the reason for the low price) is the
limited bandwidth. To observe signals accurately, a good rule is to have a
'scope that has a vertical bandwidth at least 10 times the highest
frequency
waveform you will be observing. That puts an upper useful frequency limit
of
about 10 MHz on that scope.
It'll certainly show waveforms up to (and beyond) it's rated 100 MHz, but
the amplifiers in the 'scope will "clean up" any aberrations in the
waveform
so you can't see what it really looks like. For example, if you put a
square
wave into the scope at 100 MHz, expect to see a nice, clean sine wave on
the
display! That's because a square wave has harmonics going up to at least
10
times the signal frequency, and unless your scope can faithfully reproduce
those harmonics it won't show a very true representation of your signal. A
10 MHz square wave will look pretty accurate on the display since the 100
MHz bandwidth will handle all the harmonic energy needed to reproduce the
signal.
In the real world of working on HF gear, what such a scope will tend to do
is to fail to display many high-frequency aberrations or parasitic riding
on
a lower-frequency signal, when those things are at or above the upper
bandwidth limit.
Also, the accuracy of the vertical amplifier "gain" (and so the accuracy
of
the amplitude of the trace on the display) suffers as you approach the
veridical amplifier bandwidth specification.
All that said, most adjustments needed on Amateur HF gear can be carried
out
at frequencies below 10 MHz, so that scope would find plenty of use on a
Ham's workbench. I have a 200 MHz scope and only occasionally have to
think
about the bandwidth issue working on HF gear. Like any tool, understanding
its limitations is as important as understanding its features.
My 'scope is an HP, so I'll leave any suggestions about the value of that
particular model to those here who follow the Tek scope line.
Ron AC7AC
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