I'm trying to build the current transformer pickup that i discussed about here(http://www.8052.com/forum/thr...ead=99362) a little before,but searching the electronic market here i was Unable to find suitable sized C like ferrites,there are only little ones available ,so i am thinking of some ways around :

1- take an EI ferrite ,then cut the middle section of the E and convert it to C ,(Don't laught at me if this is so foolish!! ;) )

2- buy some EI ferrites and use the I section to build a box around the wire.

3- use a toroidal ferrite and cut out 1/5 of the circumference leting the cable to reach the center of ferrite.

4- use a very big toroid and disconnect the Spark wire and connect it throught the toroid's center.

what do you think about these ,any comments ?
Farshid J.H.