Video: https://youtu.be/dkxOwAX-kz8 Simple yet fairly performant analog spectrum analyzer built using fairly easy to get parts. Input voltage sweep should be a Sawtooth with adjustable offset (center frequency) and amplitude (sweep width). Input voltage sweep is connected to the X deflection input of an oscilloscope. Output of this circuit can be amplified and peak video detected or simply connected directly to the Y deflection input of an oscilloscope. Peak output amplitude with 20 Vpp input signal is around 1,4 Vpp. This design is more of a curiosity than a useful instrument although it may prove useful in emergency situations. I personally wanted to try to design and build an analog spectrum analyser without any ICs as a proof of concept. I would reccomend to wait for the version 2 where I want to use OPamps for LO VCO and precise sweep control, LM1496 double balanced mixer, a lot narrower crystal filter as well as a logamp detection for at least 40 dB.