# Thread: Wire Tension & Inductance

1. ## Wire Tension & Inductance

Understanding that higher tpl results in higher inductance, does wire tension likewise increase inductance with an increase in tension? Or is the other way around?

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2. Not TPL by itself but actual number of turns.

Of course, if you fill up a coil form with higher TPL, rising wire tension so you can fit more in same space, then you can fit more turns there, and that is the proper parameter to consider.

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3. Only marginally, as far as it reduces loop area and turns count.

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4. Thanks. I am puzzling over an original Filtertron that needs repair. The coil is wound so loose it's...surprising. And the inductance is lower than I would have expected. I would a replacement coil but the inductance was much higher so I'm trying to work out what's happening.

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5. Well, you definitely wound more turns than what was previously there, thatīs for sure.
By the way, your rewind will also be hotter

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6. ## Look, in the sky! It's a bird! It's a plane! No, it's Kibbitzer Man!

Originally Posted by jrdamien
...I am puzzling over an original Filtertron that needs repair...
And the inductance is lower than I would have expected.
You know that the inductance of a coil is inversely proportional to its length, right? So (all else being equal) a tall bobbin will have lower inductance than a short bobbin with the same number of coil turns. But of course the biggest decider, inductance wise, is the relative permeability of the core material.

Originally Posted by jrdamien
I would a replacement coil but the inductance was much higher so I'm trying to work out what's happening.
IIRC, an original Filtertron coil would have about 3000 turns. How many does your replacement have?

Shalom,
rb

EDIT: I see that Juan posted while I was tending the kugel.

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7. "So, all else being equal, a tall bobbin will have lower inductance than a short bobbin with the same number of coil turns.'

I think you have that backwards. Tall bobbin, more surface area of the core for the wire to contact, higher inductance. A shorter bobbin will be fatter, thus the wire is further away from the core thus less inductance.

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8. Originally Posted by mozz
"So, all else being equal, a tall bobbin will have lower inductance than a short bobbin with the same number of coil turns.'

I think you have that backwards. Tall bobbin, more surface area of the core for the wire to contact, higher inductance. A shorter bobbin will be fatter, thus the wire is further away from the core thus less inductance.
tell that to the P90 bobbin.......

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9. So, all else being equal.............................

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10. Originally Posted by jack briggs
tell that to the P90 bobbin.......
Huzzah.

Originally Posted by mozz
So, all else being equal.............................
Yea, I was being intentionally ridiculous.
But, ignoring that a pickup bobbin isn't really a solenoid, the inductance of a solenoid is really inversely proportional to its length.
You'll have to ask a physicist to explain why, because I can't. (Not without slogging through some physics text, anyways.)

Of course, this is all a red herring. I strongly suspect, along with Juan, that OP overwound his replacement coil.

-rb

EDIT: Forgot to put this in:

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