- Feb 2, 2010
>Hi! On the topic of shielded loop, can anyone tell me if the metal forbuild a loop is important electrically speaking. I've read on this group
that aluminum or copper are preferred. Is this because they are non
magnetic metal? I have a round piece of metal that I could use to build a
shielded loop but it is magnetized metal. Any idea? Thanks
Copper or AL is used because it has less RF resistance than
iron. Also, those two metals won't have a tendancy to rust
The metal "shield" is actually part of the antenna. You can
prove that to yourself by touching the metal loop and noticing
that the loop detunes when you touch it. So, really, if your
loop is mounted "in the clear", it doesn't make a bit of
difference in sensistivity or directivity whether it's shielded
or not (read more below). If the loop is very near some
metal objects, there might be some benefit of having the shield.
A loop that is UN-shielded may have a higher 'Q' because of
less distributed capacitance....depends on how it is wound.
Having a higher 'Q' usually results in a more sensitive
loop, but with narrower (sharper) tuning. The crystal
radio boys know this and some have constructed
large loops of large litz wire (the right type of litz) for
that very purpose.
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