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From Posting #91. Very great care must be taken in both choosing
construction ma-
terials and avoiding accidental ferro-magnetic contamination. An
invisible iron
filing will cause the signal decay TO BE REDUCED BY A FACTOR OF TWO
OR MORE.
The winding wire should be as pure as possible. Undoubtedly the
failure of some coils
is due to the few parts per million of iron in the copper wire....
[ATSM standard B5 for electrolytic copper requires 99.9% Cu and
standard B170 for
oxygen-free requires 99.95% copper wire. One firm advertises that
they can provide
99.999% pure copper wire on special order. Unless excessively
expensive probably
best to use it and be safe. POSSIBLE test for iron content is: Try
running a high
DC current through the wire, (high enough to raise it to "letgo"
temperature)
shutting of the current, and looking to see if it has any residual
magnetic prop-
erties. I don't know if a compass would be sensitive enough for
this experiment
or not. You might also try winding an air-core coil from it,
running a square
wave through it, and looking for hysteresis effects, but this is
only a guess. -
added by das with input from others.]
I find the same firm which will custom make the 99.999% pure copper
wire can also
provide square and rectangular wire. Does anyone have any idea if
this would be
better, worse or no practical effect?
Posting #91 continued...metal inclusions can occur in plastic piping
...par-
ticularly true of recycled plastics. It is also possible that
coloring materials
used in the plastic contains iron minerals which will degrade
performance. Also
note the comment from George Davidson that one time he wound up with
epoxy
that had ferrous contamination.
construction ma-
terials and avoiding accidental ferro-magnetic contamination. An
invisible iron
filing will cause the signal decay TO BE REDUCED BY A FACTOR OF TWO
OR MORE.
The winding wire should be as pure as possible. Undoubtedly the
failure of some coils
is due to the few parts per million of iron in the copper wire....
[ATSM standard B5 for electrolytic copper requires 99.9% Cu and
standard B170 for
oxygen-free requires 99.95% copper wire. One firm advertises that
they can provide
99.999% pure copper wire on special order. Unless excessively
expensive probably
best to use it and be safe. POSSIBLE test for iron content is: Try
running a high
DC current through the wire, (high enough to raise it to "letgo"
temperature)
shutting of the current, and looking to see if it has any residual
magnetic prop-
erties. I don't know if a compass would be sensitive enough for
this experiment
or not. You might also try winding an air-core coil from it,
running a square
wave through it, and looking for hysteresis effects, but this is
only a guess. -
added by das with input from others.]
I find the same firm which will custom make the 99.999% pure copper
wire can also
provide square and rectangular wire. Does anyone have any idea if
this would be
better, worse or no practical effect?
Posting #91 continued...metal inclusions can occur in plastic piping
...par-
ticularly true of recycled plastics. It is also possible that
coloring materials
used in the plastic contains iron minerals which will degrade
performance. Also
note the comment from George Davidson that one time he wound up with
epoxy
that had ferrous contamination.