I'd say this is just aggressive SEO, with you looking for a specific digital “product” of schematics. I get similar experience in regular search when looking fo

I'd say this is just aggressive SEO, with you looking for a specific digital “product” of schematics. I get similar experience in regular search when looking for manuals for appliances and such. As for ‘spectrum analyzer’ instead of ‘network analyzer’, it's probably Google's wonderful synonym substitution, which considers ‘music’ and ‘noise’ interchangeable, or similarly with ‘Saint Petersburg’ and ‘Moscow.’