"Fred McKenzie" wrote in message
...
In article ,
"Dave" wrote:

Gotcha! (I think.) So I should wind half my turns with A to a, then
connect a to B and wind the other half. Have I got that right? Or do I
Wind A to a and then wind B to b over that (not actually connecting one
to
the other), using B as my CT?

Dave-

How critical is your center tap? If it important that the tap be
perfectly centered, it would be better to use one bi-filar winding
instead of the two separate windings you describe.

If possible, spread the turns out over the toroid so the end is next to
the beginning, so the center tap can be easily connected.

If there are a lot of turns using small wire, you can first wind the
wire pair onto a shuttle (a long, skinny flat spool). Then unwind it
from the shuttle while passing it through the toroid. With lots of
turns, it might help if the two wires were different colors. Otherwise
you would need an Ohmmeter to determine which is which.

Fred
K4DII

Hey Fred,

Actually, I realized after I posted that last one that it is not actually a
"center" tap. It is tap about 20 to 25 % up from the start, in a 2 uH coil.
The original plan called for an 8-turn (on a 1.5 in form) air core coil with
the tap on the second turn, but I am wanting to modify that to use two
switchable coils with as little interference between them as possible, thus
the toroids rather than air-core coils. My calculations tell me that a 2 uH
coil (on an Amidon T-50-2 toroidal core) would have 22+ turns, so I am
guessing the tap would be around 5 or 6 turns. Question: could I wind the
first coil (for 2 uH) and then overlay it with the second (for the five or
six turns), connecting them at the beginning and hooking up their respective
ends to the appropriate components? If desired, I can upload the schematic
I am wanting to modify. It is the oscillator described in the
Hands-on-Radio column of QST in the Aug/Sep/Oct/Nov issues (experiments
#43/44/45/46 in the series.) The original idea was a Hartley osc. that
ended up becoming a crystal-controlled transmiter for the 40 meter band, but
I am wanting to use the osc to build a makeshift signal generator for
testing another project. (I don't have a signal generator currently, thus
the attempt at building a makeshift one.)

Apologies if this is too confused. I am obviously a newbie. If all of this
is so far off-base as to be hopeless, just tell me so and I'll try not to
bother again.

Thanks,

Dave