More test about Slug Tuned Inductor

This page investigates some inductor I have got. As always one can never find andy info about the coils and there is no manufacture label either so I have to investigate more.

All contribution to this page are most welcome

I have made 4 coils with different number of turns. I made 6, 8, 12, ans 28 turns.
There is a formula for coils I will use and I have the been using a LCR meter to measure the inductance of the 4 coils. The values are plotted in excel to form a curve and from the curve I can calculate the AL value.
Formula : L (nH) = AL*n2

Where:
L = inductance in nanohenrys
AL = inductance factor
n = number of turns

This first diagram show the inductance with the screw-slug removed.

The red curve is made by excel and is a trendline. The inductance vary from 150nH to 3263nH.
The formula of the trendline is 3.2833 x 2.0681
If you compare this formula to he first one you can see the similarity.
The exponent is very close to 2 and the AL value will therefore be 3.28

The next diagram show the inductance with the screw-slug screwed to the bottom position.

The red curve is made by excel and is a trendline.
The inductance vary from 457nH to 9113nH.
The formula of the trendline is 12.514 x 1.9734
The exponent is still very close to 2 and the AL value will therefore be 12.51

Conclusion: The ferrite slug core raise the AL from 3.3 to 12.5, depending on how deep it is screwed into the coil.
The tables below show the complete data. The position of the slug-core is in percent of the total lengt of the core. If there is no core the value is 0% and if the complete core is screwed into the coil the value is 100%

n = 6
Core position (%)
Inductance (nH)
0% (no core)
150
16%
170
33%
209
50%
285
67%
372
83%
440
100% (max core)
457
n = 8
Core position (%)
Inductance (nH)
0% (no core)
198
16%
217
33%
265
50%
341
67%
464
83%
657
100% (max core)
700
n = 12
Core position (%)
Inductance (nH)
0% (no core)
624
16%
640
33%
690
50%
837
67%
1091
83%
1425
100% (max core)
1701
n = 16
Core position (%)
Inductance (nH)
0% (no core)
982
16%
1056
33%
1265
50%
1650
67%
2154
83%
2659
100% (max core)
2957
n = 28
Core position (%)
Inductance (nH)
0% (no core)
3263
16%
3546
33%
4110
50%
5199
67%
6728
83%
8240
100% (max core)
9113

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