Posted on Feb 5, 2014

The information here is primarily intended for home brewers that want to build the analyzer or want to design their own based on the principles of the design. It is not intended for use in commercial applications ! If you want to build the analyser a warning is in order: First make sure you can get hold of all the components. One of the de

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sign objectives was to use easily obtainable components. Well I must admit I failed miserably because I used components I had in stock and did not check for their availability. It turns out that some of the key components are obsolete and hard to get. The table below may help you find equivalents and/or possible sources. The VCO is a Hartley oscillator tuned by a BB212 varicap. Its frequency is controlled by a MC145170 synthesizer. The clock frequency of the synthesizer is 10. 240 MHz. It is divided by 1024 to produce a 10 kHz reference frequency. So the VCO is tuned in increments of 10 kHz. The controller software allows you to select the actual step size from a 10, 20, 100, 200, 500, 1000 kHz sequence. The VCO signal is fed to two NE602 mixers. The LO signal for the mixers is generated by a Colpitts X-tal oscillator at 48 MHz. Two RC combinations of 100 © \ 33pF provide the +45 ° and -45 ° phase shift. The output of each mixer is buffered by an emitter follower. The second mixer also provides the measurement signal. (the NE602 outputs are used as single ended outputs) Either I or Q is selected by a diode switch and fed to a fifth order LPF at the LO input of the synchronous detector. This is also a NE602. Another diode switch selects either Voltage or Current to be connected to the input of the detector. The differential output of the detector is fed to a differential amplifier on the controller board. The output is...

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