Adafruit has released a tutorial showing how to build a portable TFT screen based Raspberry Pi RTL-SDR spectrum analyzer that was inspired by the HackRF portapack. Construction of the project is very simple and the “FreqShow” python software is provided a
Let's put together a pixel strip with an an Arduino UNO and the Spectrum Shield to build a seven bands "large" Spectrum Analyzer of simple construction.
This animation shows how the resolution bandwidth of a swept-tuned spectrum analyzer is affected by the IF bandpass filter. Notice that wider bandwidth filters are unable to resolve the two closely space frequencies and the LO feedthrough causes the appearance of a baseband signal.
Making an audio spectrum analyzer with a microcontroller