[Amps] Line Isolators for RF feedback

[peter.chadwick at Zarlink.Com]

Hal said:

>quickly saturated the cores, heated things up and made for squirrely 
tuning, 

The cores can get hot before they saturate, just by virtue of the energy 
used moving the domains around the B-H curve.

I suspect that because of their permittivity, a high voltage on them can 
lead to a capacitive displacement current through the ferrite, leading to 
heating, too.  Some of the 'lower loss' ferrites, meant for VHF 
applications (e.g. ferrite rod antennas in pagers) can be very susceptible 
to magnetic fields, driving them to a point on the B-H curve where they 
lose properties. One place I worked about the time the Weller irons with 
Curie point temperature control came in ruined a batch of 200 expensive LC 
filters because of the magentic field of the newly provided Weller irons 
on the production line affecting the ferrite!

Of cousre, the production people blamed engineering, and tried to charge 
it against our budget!

73

Peter SM/G3RZP