LTspice - modelling a typical MW radio mixer (converter).
Let's have a MW radio input frequency fi=540kHz and oscillator of fo=1000 kHz.
In transistor collector is a filter to get out the intermediate frequency fm=fo-fi = 460kHz.
As a template (not in all details) was taken Siemens RT711A from
Measuring voltage out(green) and mix (blue):