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Hi guys,
This is not a crude summary - it is a very good summary. Thanks
for putting it all together, Dale.
From the physics viewpoint, the toroid doesn't have to be
exactly perfect. The crudest approximation to the toroid, the
square with four solenoidal cores, in its worst orientation, also
gives you exactly half the signal of the best orientation - just
like the toroid. It also will be quite good for cancelling outside
interference. However, some of the internal magnetic field will
'leak' outside at the corners meaning you cannot shield it quite as
closely as you can a toroid.
For a toroid, all the field is inside the winding so you can
wrap the thing in aluminum foil to shield it. For the square
configuaration, you'd have to have some space between the coils and
any shielding. However, if this is not a problem (i.e., if you have
the room to put a bigger shield around it) or if you don't want to
bother with shielding in the first place, the square should be quite
good.
If you opt for a toroidal form, you don't have to worry about
minor imperfections in the toroid - as long as it is APPROXIMATELY
toroidal, it should be OK. I thought the PVC tubing version with
the 45 degree elbows suggested by Duke would be quite good - I have
not tried it myself.
Jim
This is not a crude summary - it is a very good summary. Thanks
for putting it all together, Dale.
From the physics viewpoint, the toroid doesn't have to be
exactly perfect. The crudest approximation to the toroid, the
square with four solenoidal cores, in its worst orientation, also
gives you exactly half the signal of the best orientation - just
like the toroid. It also will be quite good for cancelling outside
interference. However, some of the internal magnetic field will
'leak' outside at the corners meaning you cannot shield it quite as
closely as you can a toroid.
For a toroid, all the field is inside the winding so you can
wrap the thing in aluminum foil to shield it. For the square
configuaration, you'd have to have some space between the coils and
any shielding. However, if this is not a problem (i.e., if you have
the room to put a bigger shield around it) or if you don't want to
bother with shielding in the first place, the square should be quite
good.
If you opt for a toroidal form, you don't have to worry about
minor imperfections in the toroid - as long as it is APPROXIMATELY
toroidal, it should be OK. I thought the PVC tubing version with
the 45 degree elbows suggested by Duke would be quite good - I have
not tried it myself.
Jim