Just wanted to share my experience with the NB in one of my boat anchors,
the yaesu FT-401B (tube rig) from the 70's.
This NB works almost as good as the best ones I have tried, it does not
introduce any distortion in even the strongest signals and has only an
on-off switch. (no level adjustment from the rig's front panel even though
it does have an internal one via a pot seen at the schematic).
This is a NB working at the 3.180Mhz IF of the rig, and the only ill effect
I have noticed when turning it on is a reduction of the IF gain which has
never made any weak signal unreadable, and of course could be potentially
compensated by one subsequent amplification stage anyway. It does though
work VERY well for any type of pulse noise.
Just with 2 "prehistoric" FETs and 2 transistors, it has to be the most
basic NB design in any rig...
Just some food for thought about future improvements in the KNB2 which may
not necessarily have to be too complicated.
For anyone interested, I have scanned a picture of the NB schematic at the
following link:
http://photothru.com/share_photoalbum.asp?aid=xA2EF4B&apwd=marko45966&guest=sv9dru@...If you have any trouble accessing it, I can email individual copie to anyone
interested.
73,
Marinos, ki4gin
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