[roberts]

Ok skim look on this tells me that coils are fully resonant.Must be tuned critically.
There are rx and tx parts directly coupled. I have been seen something simillar in the past
only cant remember exactly where?
I guess this part (middle of schematic) is taken from some old md bfo project.Probably from those in patents database.
Should search trough databases to find exact match. Designer, here used simpliest possible bfo approach and
added sort of direct receiver (down part of schematic).
So it seems receiver is able to pick only eventuall differences in balance occured in metal vicinity.
I guess this will somehow "detect" some metal. Logically metal in coil vicinity will slitly disturb
balance. But i still do not see great benefits from this?
This will indeed react only at very short distances. Maybe 10-20cm on larger metal items...maybe.
Why added direct receiver while classic bfo md has already possibility to indicate balance disturbances?
I dont have a clue? I guess designer experimented just to see results, without much of idea.
Also, we have here two "received" signals - two informations (very rough).
The one from RX coil and the one from ferrite rod direct receiver.
Ok principle here is almost understandable. But what benefits from this one?
I dont see quite benefits at all.
I'll repeat, this will "react" only at very short distances.
It is to early to make some conclusions.These were my preliminary observations. I could be wrong.
So for now i will stop saying anything and return to analyze.
I am not bugging myself here with distances. I am sure those are very low. Just want to examine
this design full and decide if it is usefull or not.
So far it looks just as pretty rough and obsolete approach,taken from some old patent from early XX century.
This will continue...