I have mentioned to a few people that I built the LMS Impedance Bridge published in both QEX and QST by Dr George R. Steber, WB9LVI. The design can be found at http://wb6dhw.com/RLC_Meter/N%20LMS%20Impedance%20Bridge.pdf . Indeed I thought that I had written it up for the CARC blog, but when I went to look for it I remembered that I had delayed writing it up because I got bogged down trying to compare the results of a number of LCR meters at the G3YSX QTH.
The thing that brought this to the top of my mind, was the following design by Rik Strobbe ON7YD http://www.rcl-meter.strobbe.eu/index.html which shows an even simpler version using just two resistors and two capacitors. Rik, ON7YDD is well know for his excellent technical work on LF communications. The only downside with Rik's design, in common with all of these instruments, is that it requires an audio card with line in (i.e. with stereo in), and unfortunately these are only to be found on desktop machines or on the more expensive USB sound "cards".
I have not tried the ON7YD version of the LCR bridge, though I expect that I will, if anyone does build one I would be interested in reports on its performance.
- Stewart/G3YSX
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