Short Wave Coil

[Mark Hennessy]

I have plenty of thick copper, and can straighten it easily by putting one end in a vice, and heaving on the other end with a large pair of pliers.   But I have not yet figured a way of winding it into a large coil such as the spring - the turn spacings always come out uneven!

Here's how the big machines do it:

https://www.youtube.com/watch?v=ieDrCR8xErI

I wonder if there's a way of adapting the technique on a smaller scale DIY basis?

No idea why, but I really enjoy watching those videos. There's something hypnotic and very beautiful about them

[Sparks]

The coil-winding video was brilliant!      Maybe it has given me ideas.    Looked up Bifflar, and it was all in French, finally found it as "Bifilar coil,"    All a clear as mud to me!    
Bob

[pwdrive]

Sorry, my apologies for the spelling, bifilar coil is easy, hold between thumb and forefinger two wires side by side and get winding, I've done that when building regen shortwave receivers, makes for nice turns spacing and the spacer wire can be unwound until there's just a few turns left, full winding is for tuning and use those few turns left of the spacer wire for a coupling winding, neat and simple.

Lawrence.

[Sparks]

I can wind the double wires on easy enough, but after securing the end and removing the spacing wire, it invariably loses its even spacing. Maybe it is because I tried it with a slippery former (piece of plastic plumbing pipe!)
Bob

[pwdrive]

I did mine on a paxolin former with a thin layer of wax put on the former before winding, some thin strips of double sided sticky tape might also work, I find that turning the former rather than winding the wire over and over always makes a better job.

Lawrence.

[Sparks]

I agree. On the rare occasions that I make coils, I always turn the former.
Bob

[Sparks]

Here is a simple HL2 receiver with one of my home-made "drainpipe" coils.
Bob

[pwdrive]

That looks very nice, I'll put yours to shame with the last masterpiece regen I made :

 

   

Lawrence.

[Mike Watterson]

Yes, I've used a couple of strips of double sided thin tape, not foam, also turn former and keep tension on wire.

[Sparks]

The big TRF looks complicated, has a look of multi-waveband and mains powered as well I note some metal valves in it. I prefer the glass versions myself. If any metal ones fall into my hands, I get rid of them as soon as possible. I eventually converted my HL2 receiver to an EF91 receiver as EF91s are very cheap and plentiful.
Bob