Inspiration – or how to cheap RX for band 3 cm?

It's going surprisingly well very easily, but let's start from the beginning…

I received a gift from an older Alcoma MW line, originally used in our Inet network. Pavel OK1VEI directed me to Aleš OK1FPC, which quickly led me astray – these devices for X-band, they are designed for broadband transmissions and cannot really be used for narrowband communication needs. But he drew my attention to the new commercial SAT LNB, which already have phase lock instead of DRO – But, thanks a lot for this tip!

The others would then, according to my first thoughts, in conjunction with the RTL-SDR USB stick should have been relatively simple. A few questions to Uncle Google and YouTube supported this idea.
Evidently, I am far from alone who was interested in such a combination of two available technologies. I found several interesting videos of successful attempts, e.g. these: 1 2 3

And what is the practical use of this gadget? Outside of YouTube demos, one use is easy – even in the case of