Mine came fully calibrated and remains calibrated after 6 years. There
was no real manual with it.

Why do you think it yours needs recalibration.

Deacon Dave, W1MCE

Zeca wrote:

Hi all,

Picked up a 2nd hand Daiwa CN-410m crossed needle SWR
meter the other day.
I want to re-calabrate it and check it out.
Can anyone help with a circuit diagram or know where I
can get one from?
Maybe the original manual had it in?

Tnx and 73

CMP