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Thread: Wire Tension & Inductance

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    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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    Old Timer J M Fahey's Avatar
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    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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    Juan Manuel Fahey

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

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    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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    Old Timer J M Fahey's Avatar
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    Well, you definitely wound more turns than what was previously there, thatīs for sure.
    Thereīs your difference.
    By the way, your rewind will also be hotter

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    Juan Manuel Fahey

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    Quote Originally Posted by jrdamien View Post
    ...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.

    Quote Originally Posted by jrdamien View Post
    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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    Last edited by rjb; 12-01-2017 at 02:38 AM. Reason: Added parentheses
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    Supporting Member mozz's Avatar
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    "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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    Quote Originally Posted by mozz View Post
    "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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    So, all else being equal.............................

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    Quote Originally Posted by jack briggs View Post
    tell that to the P90 bobbin.......
    Huzzah.

    Quote Originally Posted by mozz View Post
    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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