Brian Howie wrote:
In message , bilou
writes

"Brian Howie" wrote in message
...

I've a 5 foot Octagonal loop for MF. The shield is copper water pipe, with
a gap , 7 turns inside plus a coupling winding. It does a good job
eliminating local noise (mostly ASDL hash from the phone lines) compared
with a vertical. However the capacitance between the shield and turns
seems to load it quite a bit meaning I can't get the tuning range I'd
like.

Brian GM4DIJ
--
Brian Howie
Hi
My own experience is that ,at least for receive, multi turn loops are
useless.
Instead you can use a single turn one with a good coil in serial.
The tuning range for a given variable capacitor is much greater
especially if ,at low frequency, the coil is using ferrite .
Switching the coil can increase the tuning range easily.
The coil, with a secondary winding,is also very useful to
adjust the coupling to the receiver.

I'd have thought I'd get a better signal from more turns, but maybe
better coupling and a higher Q from your suggestion would do the same.

Brian

To be a bit simplistic, the amount of signal captured is proportional
to the loop area; the number of turns has little to no effect on that.

The number of turns greatly effects the inductance.

Multiturn loops are used at VLF frequencies to get the inductance large
enough so the loop resonants with a practical capacitor.

Unless you are trying to operate on the 2200 meter band, forget multiple
turn loops.


--
Jim Pennino