[Top] [All Lists]

Re: [TenTec] OT: Scopes

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] OT: Scopes
From: "Charles P. Steinmetz" <charles_steinmetz@lavabit.com>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Mon, 20 Feb 2012 06:03:27 -0500
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
Richards wrote:

>What can one do to avoid getting a lemon or broken
>or poorly calibrated,  or whatever broken,  oscilloscope
>at the local hamfest ?

As others have suggested, a seller who is willing to give you a 
money-back guarantee is one possibility.  Expect to pay for this privelege.

Otherwise, Be Prepared.  If you are planning to look for a scope, 
bring enough stuff with you to test one -- a signal generator of some 
sort with at least semi-accurate amplitude and frequency, a 10x scope 
probe, and a BNC cable (for direct 1x input).

The signal generator need not be a commercial item, and its frequency 
and amplitude need not even be variable.  A 1 kHz square wave at TTL 
level (5 V p-p) is enough to get a good idea of the basic functioning 
of most any scope, and can be built with almost nothing in a small 
box that runs on batteries.  Note that most scopes have such a signal 
available for adjusting probe compensation, so you may need only a 
probe and a power outlet.

If you want to get really fancy, build a little box with a 1 MHz CMOS 
crystal-controlled clock generator and some decade dividers and 
attenuators to generate signals from 1 MHz down as far as you want to 
go at levels from 5 V p-p down to however low you want to go.  Or 
bring your choice of commercial signal generators (for example, a Tek 
TM-50x cabinet with most any FG5xx, PG5xx, or SG5xx module).

All of this assumes that a power outlet is available, as one almost 
always is somewhere at a hamfest.  If your signal generator requires 
AC power, bring a cube tap in case there is only one outlet.  Bring a 
"ground adapter" in case the outlet you find is not three-prong.

However: If you are not confident of your ability to tell whether a 
scope is working satisfactorily given such a tool, then you need your Elmer.

Best regards,


TenTec mailing list

<Prev in Thread] Current Thread [Next in Thread>