[TowerTalk] TowerTalk Digest, Vol 203, Issue 6

[Rudy Severns]

GM all,

To build a stable high Q inductor with a predicable value using high
permeability manganese-zinc ferrites, like Fair Rite type 77 for example,
you will need to use an air gap.  Even a small air gap drastically reduces
the effective permeability but in exchange you get value stability.  Gaps of
a few mils are typical.  The design process is a trade-off between gap size
and copper loss, i.e. more gap more predictable the value but less effective
permeability means more turns for a given inductance.  

GL and 73, Rudy N6LF