Home-made Coil Formers

Hi this is just a brief technical note with some ideas of how to make your own simple coil formers using some simple easily available materials. These ideas came about when making my latest project, a simple RF signal generator. I thought they may be of use and were worth a mention in their own right. The problem I needed to overcome was obtaining suitable formers for the coils. The two main methods are shown below:-

Method 1 using a standard coil former and tight fitting rubber grommets

Method 2 Using Sewing machine bobbins and either dowel, plastic rod or a coil former

Both these methods are similar to do the major point is the grommets must be a tight fit to prevent the coils from moving, they can always be glued in place after winding.

In both approaches the number of individual coils can easily be changed on the former by either using more grommets and/or bobbins. In method 2 using the bobbins it is easy to vary the coil coupling by placing two grommets between the sewing machine bobbins and varying the coil separation, a pair locking each bobbin in place.

The final touch would be to cover the coil / assembly in shrink fit plastic tube including a label. I have seen several other methods used including plastic/card disks, but these method s are easier to use and use "accurate" sizes of coil.

Method 1 is also particularly well suited for use inside reused IF cans eg the toko 10K series.. Other ides I have seen are for space wound coils

1 twin windings with a wire and a fishing line wound side by side
2 plastic screwed rod with the conductor being wound in the threads this could even be drilled out to fit a standard coil form as in methods 1 and 2.
and:-
3 for larger diameters even flexible grommet strip.
I will leave it to you to calculate the number of turns etc for a given inductance value.

Please note I do not supply kits, parts, PCB's or build boards for my projects but am more than willing to help talk you through a build or fault finding via my normal contact methods, or even SKYPE if required for direct contact.