I know wire diameter and direction of turns are critical, but if that is covered can't you just rewind a coil based on resistance, or more clearly length instead of turns? The resistance/ft. is known value for any new wire.

Most coils have windings on top of one another, so reistance per turn varies in a complicated way.

:I know wire diameter and direction of turns are critical, but if that is covered can't you just rewind a coil based on resistance, or more clearly length instead of turns? The resistance/ft. is known value for any new wire.
:

Doug,
Don't you mean REACTANCE varies. Resistance per foot/turn is a fixed quantity, depending gauge of wire.

marv

:Most coils have windings on top of one another, so reistance per turn varies in a complicated way.
:
:
:
::I know wire diameter and direction of turns are critical, but if that is covered can't you just rewind a coil based on resistance, or more clearly length instead of turns? The resistance/ft. is known value for any new wire.
::
:

Marv, maybe I misunderstood, but I though he was proposing to wind a coil without counting turns - just keep winding it until the resistance comes up to whatever it would be with a fixed ohms/turn.

I guess you could measure the resistance of the original coil, and wind the same wire, in the same pattern, until you got to that resistance. But then, if you could measure the resistance of the original coil, why replace it in the first place? Huhh? Huhh? ;>)

:Doug,
:Don't you mean REACTANCE varies. Resistance per foot/turn is a fixed quantity, depending gauge of wire.
:
:marv
:
::Most coils have windings on top of one another, so reistance per turn varies in a complicated way.
::
::
::
:::I know wire diameter and direction of turns are critical, but if that is covered can't you just rewind a coil based on resistance, or more clearly length instead of turns? The resistance/ft. is known value for any new wire.
:::
::
:

Because quite often there is more than one coil of the same value/resistance, and also the resistance of the coil is often on the schematic?

:Marv, maybe I misunderstood, but I though he was proposing to wind a coil without counting turns - just keep winding it until the resistance comes up to whatever it would be with a fixed ohms/turn.
:
:I guess you could measure the resistance of the original coil, and wind the same wire, in the same pattern, until you got to that resistance. But then, if you could measure the resistance of the original coil, why replace it in the first place? Huhh? Huhh? ;>)
:
::Doug,
::Don't you mean REACTANCE varies. Resistance per foot/turn is a fixed quantity, depending gauge of wire.
::
::marv
::
:::Most coils have windings on top of one another, so reistance per turn varies in a complicated way.
:::
:::
:::
::::I know wire diameter and direction of turns are critical, but if that is covered can't you just rewind a coil based on resistance, or more clearly length instead of turns? The resistance/ft. is known value for any new wire.
::::
:::
::
:

Whammo,
Here is my take on your question. If you duplicate the length of the original wire, you should also duplicate the length, diameter of the coil itself and winding style, which affects the actual reactance (microhenrys) and quality factor (Q) of the finished product. Solenoid wound coils (side by side turns/many layers) are used for power supply and audio transformers, but have lower "Q", added parallel capacitance and are not suitable for most RF/IF coils in AM radio apparatus. AM radio (RF and IF coils) are typically lattice style. There are some exceptions in the case of single layer coils on large diameter forms, as in oatmeal boxes used by experimenters and crystal set apparatus. These large diameter forms provide the req'd inductance and are easily wound without expensive equipment. The lattice coils noted above require special winding techniques and machinery, but normally cannot be duplicated manually.

marv

:Because quite often there is more than one coil of the same value/resistance, and also the resistance of the coil is often on the schematic?
:
::Marv, maybe I misunderstood, but I though he was proposing to wind a coil without counting turns - just keep winding it until the resistance comes up to whatever it would be with a fixed ohms/turn.
::
::I guess you could measure the resistance of the original coil, and wind the same wire, in the same pattern, until you got to that resistance. But then, if you could measure the resistance of the original coil, why replace it in the first place? Huhh? Huhh? ;>)
::
:::Doug,
:::Don't you mean REACTANCE varies. Resistance per foot/turn is a fixed quantity, depending gauge of wire.
:::
:::marv
:::
::::Most coils have windings on top of one another, so reistance per turn varies in a complicated way.
::::
::::
::::
:::::I know wire diameter and direction of turns are critical, but if that is covered can't you just rewind a coil based on resistance, or more clearly length instead of turns? The resistance/ft. is known value for any new wire.
:::::
::::
:::
::
:

Hi

Number of turns is what's important. If you unwind a coil and just rewind with the same length of wire unlikely that it's as smooth as original. Scramble wound takes more wire for the same number of turns.

DC resistance, as read on an ohm meter, makes little difference.

Norm

:Because quite often there is more than one coil of the same value/resistance, and also the resistance of the coil is often on the schematic?
:
::Marv, maybe I misunderstood, but I though he was proposing to wind a coil without counting turns - just keep winding it until the resistance comes up to whatever it would be with a fixed ohms/turn.
::
::I guess you could measure the resistance of the original coil, and wind the same wire, in the same pattern, until you got to that resistance. But then, if you could measure the resistance of the original coil, why replace it in the first place? Huhh? Huhh? ;>)
::
:::Doug,
:::Don't you mean REACTANCE varies. Resistance per foot/turn is a fixed quantity, depending gauge of wire.
:::
:::marv
:::
::::Most coils have windings on top of one another, so reistance per turn varies in a complicated way.
::::
::::
::::
:::::I know wire diameter and direction of turns are critical, but if that is covered can't you just rewind a coil based on resistance, or more clearly length instead of turns? The resistance/ft. is known value for any new wire.
:::::
::::
:::
::
:

The preferred methods are those described in the previous replies. However, if, for some odd reason, you cannot count the turns, but you know what the resistance should be, and you are rewinding with the same gauge wire, and hopefully in the same formation, winding to resistance might help you get into the neighborhood of the original coil's reactance. ...As a last-stitch effort.

T.