What an awesome thread this is and what a find
As a kid I had this expensive handheld scanner (Cobra SR-15) that I remember saving up forever for. It served me well, even after the NiCd became useless. One day after trying to wire it up to my car's audio system I accidentally connected a power supply wire to the audio out and fried it (one of the triacs I think).
I spent ages trying to repair it and learnt a lot in the process, particularly about the discriminator chip that was popular at the time. Alas, the circuit board itself started showing signs of the copper paths detaching and the unit is now destined for the bin (although I still have it for it's clever design).
Enter SDR - I never even knew it existed.
Thank you to those that raised the subject and posted some very insightful information. This is an incredibly cheap way of getting back into my past fun and popular hobby.