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'[EE]:winding an inductor.'
2001\06\21@142922 by Duane Brantley

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Hello everyone,

I need a J.W. Miller Magnetics inductor (#4604).  The is a 1.5uH coil on a
phenolic form.  It has a SRF of 149MHz.  These seem to be very hard to get.
I need a 1.5uH inductor with a SRF of 150 (149) MHz or greater.  I was
thinking of winding my own.  I have some #26 magnet wire, and was looking at
using a 3/16th drill bit to wind the form on.  What I don't know is long a
wire is needed or how many turns.

Any help is appreciated.  Thanks!

Duane

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2001\06\21@174019 by Douglas Butler

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part 1 1178 bytes content-type:text/plain; charset="us-ascii" (decoded 7bit)

The attached link leads to the ARRL website.  It has the formulas for
calculating inductor dimensions.  If the link fails just goto
http://www.arrl.org and search for coil winding.

Sherpa Doug

> {Original Message removed}
part 2 136 bytes content-type:application/octet-stream; name="Homebrew~Your~Own~Inductors!.url" (decode)

part 3 154 bytes
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2001\06\21@193616 by rottosen

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Duane Brantley wrote:
>
> Hello everyone,
>
> I need a J.W. Miller Magnetics inductor (#4604).  The is a 1.5uH coil on a
> phenolic form.  It has a SRF of 149MHz.  These seem to be very hard to get.
> I need a 1.5uH inductor with a SRF of 150 (149) MHz or greater.  I was
> thinking of winding my own.  I have some #26 magnet wire, and was looking at
> using a 3/16th drill bit to wind the form on.

A common technique is to wind the coil on a high value resistor and
solder the coil ends to the resistor leads right next to the body.


-- Rich


 What I don't know is long a
> wire is needed or how many turns.
>
> Any help is appreciated.  Thanks!
>
> Duane
>
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2001\06\21@201354 by Russell McMahon

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> I need a J.W. Miller Magnetics inductor (#4604).  The is a 1.5uH coil on a
> phenolic form.  It has a SRF of 149MHz.  These seem to be very hard to
get.
> I need a 1.5uH inductor with a SRF of 150 (149) MHz or greater.  I was
> thinking of winding my own.  I have some #26 magnet wire, and was looking
at
> using a 3/16th drill bit to wind the form on.  What I don't know is long a
> wire is needed or how many turns.


Inductance of a single layer coil is approximately given by

   L = (A^2. x N^2) / (9A + 10B)

L = inductance in microhenries
A = radius in inches
B = length of coil in inches
N = number of turns.

1.5 uH is "not much"
Winding a coil of roughly correct size on eg a pencil or marker as a former
and then squashing or stretching the length to get final trimming is the
time honoured method. If you can view an original coil then winding one
visibly similar will give you a good starting point.

Specing the inducatnce AND the SRF makes life tricky as you then only have
self capacitance as a variable while holding inducatnce constant. In
practice you probably get the inducatnce about right and alter the coil from
there to suit final needs.

Using above as a rough starting point it seems about 30 turns with a coil
length of 0.5" to 1" may be "in the ball park"
Sounds a few more turns than I would have expected but small radius affects
this.
YMMV.



regards





     Russell McMahon
_____________________________

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2001\06\22@040342 by Peter L. Peres

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Duane, I think that you are looking for a file called 'aircoils.html'
available at:

http://dialspace.dial.pipex.com/town/parade/rcx61/aircoils.shtml

It only goes to 580 nH. Try to build a 100 nH coil on a former with an
adjustable ferrite core, in the hope that the ferrite will get you there.
You said nothing about power levels etc.

Peter

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2001\06\22@122917 by David Minkler

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Hi,

I get 29 turns on a 1 watt carbon comp "form".  There is enough room for
this many turns on a 1 watt.  On a half watt or smaller, too many turns
are required for a single layer fit.  As Richard suggested, this
(winding on a high value resistor as a form) is the time honored
method.

Regards,
Dave

Russell McMahon wrote:
{Quote hidden}

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2001\06\23@030204 by Scott Stephens

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"A Multimode High-Frequency Inductor Model"
by Randall W. Rhea, pp. 70-80
http://www.amwireless.com/archives/1997/Nov-Dec1997/novdec1997-p70.pdf

"Filters and an Oscillator Using
a New Solenoid Model"
http://www.amwireless.com/archives/2000/v12n11/pg30.pdf

Scott

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