Practical toroid winding question

[mikekopacki]

I am almost ready to start winding toroids for my K2.  I have run into this question before but never found an answer.

Suppose I wind a toroid, then check its inductance afterwards.  I find that the value is not exactly the same value as the schematic calls for, but after removing one turn (or adding one turn), it's perfect.

Should you,

a)  use the # of turns in the assembly instructions, regardless of the value obtained, since the designer knows a lot more than I do
b)  change the number of turns, since the performance of the radio is based on the value of the inductance

Wayne and Eric, I'd like to hear your answer on this as well.

Thanks, all.  I'm now half way through the basic kit setup.

73,
Mike, NJ2OM
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[Don Wilhelm-3]

Mike,

Wind the toroids as specified - the K2 will work great with the specified
number of turns, and there are over 4000 of them already built to confirm
that statement.

Be certain to count each turn that passes through the center of the core.
If only the turns on the outside are counted, it is easy to miscount (the
two free ends constitute a turn too).

I should also ask, just how much can you trust your inductance meter?  If it
does not measure the inductance at the operating frequency, that alone may
be the answer to the mystery.

73,
Don W3FPR

----- Original Message -----

I am almost ready to start winding toroids for my K2.  I have run into this
question before but never found an answer.

Suppose I wind a toroid, then check its inductance afterwards.  I find that
the value is not exactly the same value as the schematic calls for, but
after removing one turn (or adding one turn), it's perfect.

Should you,

a)  use the # of turns in the assembly instructions, regardless of the value
obtained, since the designer knows a lot more than I do
b)  change the number of turns, since the performance of the radio is based
on the value of the inductance

Wayne and Eric, I'd like to hear your answer on this as well.



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[Ingo Meyer DK3RED]

Hello Mike,

> a)  use the # of turns in the assembly instructions, ...

Yes, like more than 4500 other K2 builder too!

> b)  change the number of turns, ...

No.
--
72/73 de Ingo, DK3RED   Don't forget: the fun is the power!

    [hidden email]   www.dk3red.homepage.t-online.de
      DL-QRP-AG   #824   www.dl-qrp-ag.de
       QRP ARCI #11295   www.qrparci.org

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[Vic K2VCO]

Mike wrote:

> I am almost ready to start winding toroids for my K2.  I have run into this
> question before but never found an answer.

> Suppose I wind a toroid, then check its inductance afterwards.  I find that
> the value is not exactly the same value as the schematic calls for, but after
> removing one turn (or adding one turn), it's perfect.

> Should you,

> a)  use the # of turns in the assembly instructions, regardless of the value
> obtained, since the designer knows a lot more than I do

> b)  change the number of turns, since the performance of the radio is based
> on the value of the inductance


The correct answer is a).  One of the things the designer knows is that the
inductance of a toroid varies with frequency as a result of the characteristics
of the core material.  So unless you are measuring the inductance at the
appropriate frequency, your measurement may not be correct.

--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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[Mychael Morohovich]

Hi, Mike-



If you check the inductance on your own meter, please note that some of the
values specified in the Elecraft manuals may vary and that differences in
individual inductance meters often increase this variation.  Elecraft
recommends that individual builders do NOT try to adjust their coils to the
exact values shown in the manual.



Mychael AA3WF

K2 #1025




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