19-10-2016, 06:45 PM
Here is a homepmade short wave coil made from a "bouncy spring" (child's toy). It worked quite well.
Bob
Bob
Short Wave Coil
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19-10-2016, 06:45 PM
Here is a homepmade short wave coil made from a "bouncy spring" (child's toy). It worked quite well.
Bob
19-10-2016, 09:09 PM
Very smart, but with a steel conductor?
Or is it perhaps nickel plated? Interesting either way that all that magnetic stuff doesn't seem to affect its function. Martin
BVWS Member
19-10-2016, 09:32 PM
Yes, probably steel. It never ocurred to me that it might not work. It is probably not magnetic anyway! The first one I made, I had the valve (an EF39) down the centre of the coil to save space, and that worked as well! This one is a neater version. I began by looking for a large spring rather than trying to wind a neat coil from copper. I had almost given up my search when I came across the slinky spring on Ebay.
Bob
20-10-2016, 08:55 AM
It works very well though! Q means nothing to me!
Bob
20-10-2016, 09:00 AM
Nice engineering job but It would work better with copper and without all the iron work, selectivity would be increased....Anyways, worrever.
Lawrence.
20-10-2016, 09:29 AM
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! I used the steel spacers simply because I got two large boxes full of them on a car boot sale. The 3mm black acrylic, I get from Ebay.
Bob
Fix one end firm and wind bifflar with a spacing wire, secure finished end firm then unwind the spacer wire.
EDIT: If it's air core then you could try this technique (also shows a spacer wire or cord): http://www.arrl.org/files/file/Technolog...708033.pdf Lawrence.
20-10-2016, 12:15 PM
Thanks for the link. That looks easy enough and quite ingenious. I have tried winding with a spacer wire and it was unsuccessful (but I didn't try very hard - limited attention span - no patience ). I have no idea what "bifflar" means, but will look it up!
Bob |
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