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G0FTD > COILS 04.09.05 10:05l 45 Lines 1587 Bytes #999 (0) @ WW
BID : 60640_GB7CIP
Read: GUEST DL1LCA OE7FMI
Subj: Re: Pile wound coil problem.
Path: DB0FHN<DB0RGB<OK0PPL<DB0RES<ON0AR<GB7CIP
Sent: 050904/0318Z @:GB7CIP.#32.GBR.EU #:60640 [Caterham] $:60640_GB7CIP
From: G0FTD@GB7CIP.#32.GBR.EU
To : COILS@WW
I previously spewed:-
> Can anyone shed any light on the following problem ?
>
> I have been constructing pile wound solenoids approx 8 x 3cm with 3 layers
> in them but I'm not convinced that the measurement I'm getting is correct
> on my equipment.
>
> Depending upon the frequency that I measure the inductance at (10Khz - > 400Khz)
> I see an inductance value between 150uH - 250uH which has several peaks and
> troughs when plotted against measurement frequency.
>
> I'm confused !
>
> How do I determine what the correct value is ?
Some bloke missing his ribs replied:-
>but I'm wondering if the ambiguity might be caused by such a simple thing as
>the differences between using solid state metering and analogue (coil) type
>metering.
Dunno - but I've come to the tentative conclusion that being pile wound
means theres going to be lots of stray capacitance caused.
As such I guess varying the test frequency when measuring the inductance
causes the odd variation.
I then hit upon the idea of finding a frequency where the coil produces
a purely reactive impedance on a test bridge, noting the freq and then
working out the corresponding reactance to impedance value.
This seems to be giving a more reliable value which I'm happy with.
Unfortunatly I'm out of reach of a decent network analyser at the moment
so I was trying to make do with simpler equipment to hand :(
Donations for the G0FTD in shack Hewlett Packard Network analyser are
most welcome ;-))
- Andy (the shopping trolley wally now with 160/80m added) -
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