Common mode choke selection beginners question

[ku637]

Hi,

While searching for common mode choke in AC line applications, found two types of description for the devices..

Some manufacturers list

1) Impedance versus Frequency (in Ohms)

some others

2) Insertion loss versus Frequency. ( in dB)

How do i convert the Impedance into dB??

Thanks for any help

 

[erikl]

I'd think a factor of 10 at impedance corresponds to 20 dB insertion loss.

 

[crutschow]

Insertion loss assumes some particular line impedance load (often 50 ohms). Using that you can convert impedance into insertion loss.