Re: LF: Paint buckets as coil forms

[Markus Vester <markusvester@aol.com>]

Hi Luis,

 

stacking buckets into one another helps to increase the inductance because the coil becomes shorter for a given number of turns. Compared to a single layer solenoid, the advantage is thus significantly less wire length and lower resistance. It is also easy to adjust the inductance over a wide range using variable spacing. The disadvantage is limited power capability due to less effective heat removal from inner layers, as well as high radial voltage gradients (especially around the return wires between the layers, connecting the top of one section to the bottom of the next). With my coil, I can now safely run up to 0.4 A into my 270 pF antenna.

 

The coil is made from seven standard polypropylene household buckets, each one carrying 480 turns of 0.4mm wire. The spacing is adjusted by Lego blocks at the rims of the bucket 

 http://df6nm.bplaced.net/VLF/VLF_110304-06/coil_legospacers.jpg

 

To wind the coil sections, I made a primitive jig with a rotatable dinner-table serving plate on the floor and an old windshield-wiper moter above:

 http://df6nm.bplaced.net/VLF/VLF_110304-06/4TS%20and%20DF6NM%20at%20work.jpg

Winding was done from top to bottom (thin end first), over some straps of two-sided sticky tape. After an initial slow learning phase, I aquired some routine in laying the turns neatly side by side, and making the whole coil ended up taking about eight hours alltogether.

 

Paul has modeled the coil using his LCnetgen software, which was able to predict the fundamental as well stray capacitances and higher-order resonances up to several 100 kHz.

 http://abelian.org/lcnetgen/ex5.html

Luis, good luck with your build, we hope to see you on Dreamer's band soon!

 

73, Markus (DF6NM)

-----Ursprüngliche Mitteilung-----
Von: VIGILANT Luis Fernán dez <luis@vigilant.es>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Fr, 29 Apr 2016 10:55 am
Betreff: LF: Paint buckets as coil forms

Hi VLF

 

In my run for "the copper thing" I called a friend which is in the industrial painting

He is going to provide me a couple of paint buckets 29cm diameter by 31cm high

I plan to test a couple of coils with 0.4mm enameled copper using this buckets as forms

If it is not the best idea, please tell me before doing it that way

 

From the coil calculators I can estimate 750 turns for a single layer coil which would be about 105mH

The buckets can be plugged one inside the other. Similar as Markus/Stefan Yogourt containers

 

Can this stacking provide an increase of inductance ?? Something aprox to have a multi layer coil ?

Not counting any help from ferrite cores dopping .... I'm afraid that more than eight bucket coils will be needed

to reach over 800mH. A lot of copper wire and time to wound it indeed

 

Multi layer winding with 0.4mm wire looks like something really hard for me. Don´t know it ir really worths the effort

 

Any ideas for a proper music track during the winding process ?? Spherics perhaps ? ;-)

 

73 de Luis

EA5DOM