Tag Archives: noise floor

Measurement of Harmonics using Spectrum Analyzers

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Occasionally I get into one of my more “techie” moods, and I feel I have to share with you an application note or white paper written by an engineer from one of the three or four big test and measurement equipment manufacturers. They really know their stuff and I think it’s worth sharing even if you don’t intend to own any of their equipment. (And maybe you do!)

In an application note (1EF78) on the measurement of harmonics, Rohde and Schwarz’ Dr. Florian Ramian discusses the theory of harmonics, problems in measuring the non-linear components of a circuit, and the advantages of the R&S®FSW signal/spectrum analyzer’s high pass filter for harmonic measurements.

R&S FSW Signal/Spectrum Analyzers

R&S FSW Series

He explains the need to isolate the harmonics generated by the measurement instrument from the harmonics of the device under test (DUT). Typically a spectrum analyzer is the measuring instrument of choice because of its ability to simultaneously display both the actual signal, and the harmonics of the signal. He describes how the high pass filters of the FSW preclude the need for further RF attenuation to the signal to reduce harmonic distortion, thus keeping the noise floor low, and increasing the sensitivity of the measurements.

That’s all I’m going to say about it. Take a look at Dr. Ramian’s discussion yourself in the Rohde & Schwarz application note (in PDF format).

If you want to take a look at the features and specs of one of the FSW’s, here’s the FSW43 on Used-Line.com.

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On Toy Telephones and Digital Test Sets

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Have you ever wondered why the ubiquitous toy telephone a toddler usually receives as a gift on his first birthday has a rotary dial and is shaped exactly like the communication device only his great-grandmother remembers using? Is there something about “ye olde” equipment that reminds us of the days when things consistently worked well?


author (Photo credit: Wikipedia)

The hardy rotary telephone rang bells in my mind recently when I read a reprinting of Benoit Leveille’s gripping 2009 tale about the effectiveness of state-of-the-art equipment versus the old tried-and-true, in EDN Network’s Tales from the Cube. In this story, the “ugly” sister, an old analog HP spectrum analyzer (could it have been the 8551A, which was introduced in 1964?) is the heroine of the story.

Leveille creates a tension-building saga that blends a repair technician’s worst nightmare—finding nothing wrong with the instrument—with a classic story-telling theme, the pauper’s triumph over the prince.

To discover how a $50,000 digital test set could not pick up a noise floor problem, which, while troubleshooting with the old “frequency-domain oscilloscope”, was found to be caused by a mere transistor gone wrong, visit the EDN Network and read “Hawk eyes, analog equipment trump expensive digital test set“.

Now I’m wondering why those toy telephones are usually painted in primary colors instead of black, but that’s a tale for another day.

See Also:
Spectrum Analyzers on Used-Line.com
Test Sets on Used-Line.com

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