[Elecraft] Toroid stuff

[Ron D'Eau Claire]

N4YM asked:

1) Is it ok if a bare portion of the winding touches the toroid?  A fellow
K2 buildr says ok.  And the pix of the KPA 100 show the wire stripped bare
right up on the toroid.

2) I am using pliers to tighten things up.  This OK?

--------------------------

1) Yes. The toroid cores are good insulators. You only need to be sure you
aren't shorting two turns together because the bare wire extends more than
one turn onto the coil. Also you need to be careful of bi-filar windings
(see below).

2) Just don't get carried away using those pliers. Cores will break and the
wire will break where it bends around the core. My copy of the manual does
NOT say the wire is pulled "tight", only that when winding with the heavier
wire it can be more difficult to handle and that the "...turns should not be
loose..." meaning very loose! The wire NEVER lays exactly flat against the
cores when wound normally. There's always some small gaps as it wraps
around. Be especially careful of the bifilar windings. The enamel can be
scraped off of the wire very easily by rubbing them together too hard. That
would produce shorts between the turns. If in doubt, check for an open
circuit between the windings BEFORE installing them on the PCB (once
installed the PCB circuit provides continuity, so you can't check that way
once they are soldered in place). 

Ron AC7AC