[RFI] Oscilloscopes

[Jim P]

Good summary of uses for an o-scope, Ford.

Add to that list these two 'uncommon' (but
valuable) applications:

- - - - - -

- Measure RF Impedances Using an O-Scope

  http://www.dallas.net/~jvpoll/tech/ph_mag.html

I came up with this methodology when faced with the
prospect of not having a commercial impedance bridge
available for use on 'a job' during an ATU change-out
years ago at a commercial AM broadcast site - it works
well and one can dynamically 'sweep' a network and
easily find resonance by observing for a null phase
difference between scope channels as well as the
amplitude 'peak' on the test port.

- - - - - -

- W8WWV - Hex Array - Using the Oscilloscope to
  Make Phased Array Measurements - by Greg Ordy

http://www.seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/HexAr
ray/UsingScope.htm

Measurements on phased antenna arrays using an o-scope.

- - - - - -

Jim P  /  WB5WPA  /




----- Original Message -----
From: "Ford Peterson" <ford at cmgate.com>
To: "john heinrich" <nd6h at sbcglobal.net>; <rfi at contesting.com>
Sent: Friday, March 04, 2005 12:41 PM
Subject: Re: [RFI] Oscilloscopes


>
> > What specs should I look for when purchasing an oscilloscope for general
use including Amateur radio?
>
> "General use" is a broad concept.  The natural response is "What do you
want to do with it?"
>
> I use an o'scope for many things.  I tune my RTTY signals using the X-Y
function on the scope.  I look at signal levels of audio.  I look at RF
signals at IF frequencies.  I check P-P output and convert to RMS using the
scope.  I inject time delays to zero in on a waveform that is delayed from
the trigger waveform.  Looking at binary signal timing is beneficial in many
circumstances, so more than two inputs may be important to you.  You can
check keying waveforms of CW.  Use it as a DC voltmeter if you want.  In all
these functions, bandwidth is important to what you intend to do.  If it's
audio, you can use some pretty simple scopes.  If you are looking at RF,
obviously the bandwidth has to be sufficient to have a calibrated output on
the screen.
>
> If you want to just look at waveforms, and not absolute timing of same, a
pretty simple indicator may be sufficient.  Likewise, if you need to look at
logic levels and determine accurate time periods, you will need a calibrated
scope with sufficient accuracy to do what you want to do.  By calibrated,
the gradients on the screen are calibrated to the settings of the horizontal
and vertical amplifiers in the scope.  Looking at wave form edges down to 1
ns or 2 ns is no real trick with a decent scope.  Doing it accurately takes
proper probes and proper setup of the test.
>
> A 100mHz scope can be usable beyond 100mhz, but the gradients will no
longer be calibrated.  In fact, without proper probes, terminations, and
test configuration, the results will be wildly out-of-line with reality.
One can be had for a couple hundred bucks on the used market.
>
> If you want to automate your tests, and convert time to frequency, P-P to
RMS, and digitally display the results, you spend more money.  If you want
to connect your scope to a computer, you will spend more yet.  Screen
capture, displaying the setup parameters and such, all are extra money and
extra nice.  Bang for the buck as they say.
>
> My 4 bay Tech 7704A scope frame actually has a handle on the top of it,
but I would hardly call it a portable.  Plug-ins are pretty reasonable at
maybe $50 to $150 each, depending on function.  Plug-ins can include
spectrum analyzers too.  So one frame can serve multi-purposes.  (time
domain vs frequency domain)
>
> Digital vs analog is another option that can prove very valuable.  Wave
form filtering may be important to you.  Selectable bandwidths can be handy.
>
> Form a budget for what it's worth to you, and go buy one.  There are
hundreds of styles and functions.  But they all display in the time domain.
So it really depends on what you intend to do with it.  If you want one that
does everything, plan on $10K or more, and even then there will always be
better available.
>
> Ford-N0FP
> ford at cmgate.com
>
>