Hi @M0GLO
Thank you for sharing the link, I will certainly have a look.
I’m always looking around for cheaper alternatives and I’ve collected a small set of circuit diagrams from various sources/books.
All of them actually need calibration.
This is one from the book “Elementi di tecnica radioastronomica”, 1977, by Gianfranco Sinigaglia I4BBE:
This one is by N5ESE, 2006:
…and this one has no reference:
mario