Hello Sat-Fans !
Update : After some requests, I offer some semiprofessional, homemade PCBs for this Konverter now on ebay.
After my converter "oldschool style" I developed and build another simple, more up-to-date converter 739 MHz to 145 MHz with just 3 active RF-components. I named it "NB-Converter tiny".
It works excellent for receiving Oscar100 NB transponder with a 2m RX.
I wrote a complete report and building instruction for it.
You can find it at : https://elektronik-muenster.de/viewtopic.php?f=17&t=34
Sorry, german language only.
But there are lots of pictures an shematics also for download so everyone should it find interesting.
In other case "deepl" helps