Problem with Superglue on selfmade DD coil

[Dixix]

I wound my first DD coil for TGSL. I was done, first coil 5.9 mH and second coil 6.4 mH.

But I think I have both coils spoiled.

To stabilize the coils I used Superglue.
Suddenly they changed induction.
First coil: 6.6 mH and second coil 7.2 mH. I could cry ....

Are the coils to use still? Or for the trash?

I guess the Superglue acts as an electrolyte in a capacitor (?).

Dirk

[Qiaozhi]

I wound my first DD coil for TGSL. I was done, first coil 5.9 mH and second coil 6.4 mH.

But I think I have both coils spoiled.

To stabilize the coils I used Superglue.
Suddenly they changed induction.
First coil: 6.6 mH and second coil 7.2 mH. I could cry ....

Are the coils to use still? Or for the trash?

I guess the Superglue acts as an electrolyte in a capacitor (?).

Dirk

The TGSL is quite forgiving as regards the exact inductance values, so the coils are more than likely still usable.
I would suspect the superglue contracted as it dried, pulling the windings closer together, and hence causing the inductance increase. Worst case, you may have to tweak the tuning capacitor values.

[Davor]

It will work perfectly even with original capacitor values because both coils acted same way (as expected), and only a resonant frequency will be slightly lower - no big deal. The effect is well known for decades, and people used to improve their coils for RF purposes using a Q-dope, which is not very different from a super glue.

[Dixix]

Thanks Davor and Quiaozhi for the hints! I am comforted. Coil development makes a lot of work. Wrap, measure Industance. Mostly it is not entirely true. Then adjust and so on.
So I have to wrap tighter next coils? And then treating with Superglue?

A big thing is the coil Calkulator from Quiaozhi. This one has been the possible turns. Great help.

Next, I will make coil nulling. I will abide by the instructions on the page 52 ItMD (Experiment 5-6).

Is that all exciting! I'm always learning new things!
Dirk

[Fabian]

Hi Dixit. My experience is that if you changing a bit the shape of your coils, you can change the inductance. Make them a little more elongated or wider and you can correct these variations of the inductance.

Regards,

Fabián

[Davor]

So I have to wrap tighter next coils? And then treating with Superglue?

Yes.
You may want to wrap a coil here and there with insulating tape that is stretched prior to wrapping. It is a proper way of using the insulating tape BTW. You always need to stretch it prior to wrapping so that it squeezes the wires you wrap.

[Qiaozhi]

Next, I will make coil nulling. I will abide by the instructions on the page 52 ItMD (Experiment 5-6).

Also read page 140 (starting at "Then follow this procedure:") and page 141.

[Dixix]

Thanks for the valuable information!

Fabian Hi Dixit. My experience is that if you changing a bit the shape of your coils, you can change the inductance. Make them a little more elongated or wider and you can correct these variations of the inductance.

I can not stretch the coils unfortunately. They are totally hard (Superglue).

Yes.
You may want to wrap a coil here and there with insulating tape that is stretched prior to wrapping. It is a proper way of using the insulating tape BTW. You always need to stretch it prior to wrapping so that it squeezes the wires you wrap.

I had used rubber band - but isolaton tape is better. You are right! Rubber band is constantly torn.

Also read page 140 (starting at "Then follow this procedure:") and page 141.

You mean it's better to make coil nulling with detector-circuit? (Page 140/141) I Will try the various options.


When I think that I start this year did not have a clue about the inner workings of MDs. The virus from the ItMD-book has infected me.
Since then I've exposed to light etched and soldered many boards. Some projects do not work. but I remained persistent. Some projects have worked well (all PI detectors). I think a PI detector is a good project for beginners ...
Also, the PI kit (Surf) from Silverdog was a nice (very good functioning) project!

Now the first IB detector ....

[Qiaozhi]

You mean it's better to make coil nulling with detector-circuit? (Page 140/141)

Yes.
The setup on Page 52 is just a simple experiment to demonstrate target phase shifts in an inductance balance coil.