Thread: Coils, why?
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Old December 3rd 07, 06:53 AM posted to rec.radio.amateur.antenna
K7ITM K7ITM is offline
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Default Coils, why?

On Dec 2, 7:09 pm, John Smith wrote:
Why not:

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etc.

A "flattened" coil, first time I see one used is Vincents' DLM, anyone?

Regards,
JS

P.S. Excuse the bad ascii graphics ...


Not a very efficient "coil." Consider what the magnetic fields are
from each wire segment. A flat _spiral_ is sometimes used, e.g. by
etching it into a PCB, though they are generally not as good as
traditional helical or toroidal coils. A stub of transmission line
less than a quarter wave long and shorted at the far end looks
inductive, too, but at HF it's a pretty inefficient way to get
inductance. They're much more useful at UHF and above.