How does one explain why one is a test equipment fanatic? Is is the idea of measuring quantities that are so small that it boggles the mind? Or is it the idea that you're able to see the trace of electrons behaving strangely? For whatever the reason, I'm passionate about old test equipment, particularly of the late 1960s to the late 1970s. Basically, post tube (valve) and pre- and early computer. In this era, both Hewlett-Packard (now Agilent ) (sigh, why didn't the test and instrumentation company keep the historical name? Answer: branding) and Tektronix produced large volumes of interesting and (now) affordable test equipment. I'm referring specifically to the HP 8410 network analyzer and the Tek 7000 oscilloscope series . The Tektronix TM500 series is also extremely useful and affordable. Another reason this era is golden is the quality of the manuals; you can learn a lot of design from reading the schematics. Right now, the manuals from HP and Tek are vapid. If you want to use the instrument, you'll survive, but if you want to know how it works, forget it .

Sampling techniques

The idea of stroboscopic analysis of waveforms dates back to the beginning of the century. Sampling forms the basis of DSP and also microwave test equipment and has been used extensively in network analyzers. The HP 8410 is an example of such an instrument (technically, the HP 8405 Vector Voltmeter preceded the 8410 in its use of sampling for magnitude and phase measurements).

Sampling has also been used in oscilloscopes. The first successful commercial sampling 'scope was the HP 180 series. This was superceded by the still incredible 1430 sampler. Tektronix followed HP by introducing the 661 and then sampling plugins, beginning with the 4S series and then the 1S series, 3S and finally 7S. More recently, both Tek and HP have eliminated the use of general purpose 'scopes as the base for sampling oscilloscopes. Furthermore, the manuals are just appalling.

Annotated bibliographies

I have collected a number of papers on LF and VLF and have put together two annotated bibliographies: one on general LF and VLF techniques and the other on LF and VLF antennas.

For further information on long wave phenomena, see the Longwave Club of America .

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