[Drake] Multimeter Suggestions for Drake Service

[djed1 at aol.com]

 In typical ham fashion, this is what I did to check my $100 Tektronix scope when I got it:  I used a calibrated Fluke to set the DC level out of a power supply, then used those levels to check the scope amplitude in DC mode.  I didn't check the AC mode, because I think it shares all the circuits with the DC mode, but you could use the calibrated AC meter to set a sine wave at a certain level, then check that the peak waveform is 2.828 times the RMS value.  Similarly, I used a frequency counter to set my function generator to an exact frequency, then used that to check the time base on the scope.  Not good to parts per million, but plenty good enough for a 1-2% scope.
Ed  W2EMN

 


 

 

-----Original Message-----
From: Jim Lowman <jmlowman at sbcglobal.net>
To: drake <drake at mailman.qth.net>
Sent: Tue, Dec 7, 2010 6:02 pm
Subject: Re: [Drake] Multimeter Suggestions for Drake Service


Good point about the RF signal generator, Garey.  I remember that, and a 

VTVM, was essential to aligning and troubleshooting Drake gear.



In the years that I was in the Air Force and working on air traffic 

control radar systems, the first thing that I reached for was a scope.

Of course, with radar, you're looking at waveforms in the millisecond 

and microsecond range that would never show up on a meter.

The spectrum analyzer was handy.  Generally an unstable AFC (we called 

it "hunting") was a sign that the magnetron in the transmitter was 

double-moding, and the spectrum analyzer showed it as plain as day.



I wish I still had access to all of that test equipment.  It was all 

top-of-the-line HP and Tektronix and the like.



Can you really calibrate a scope with a DVM?  I always wondered, when 

guys would drag these monsters away from a swapmeet, if they would be 

accurate.

Maybe if all one wants to do is look at waveforms they would be okay.  

But we had to rely not only on the accuracy of the time base, but also 

the ability to measure the amplitude of pulses.

For this reason, all of our test equipment had to go in for calibration 

at regular intervals.



73 de Jim - AD6CW

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