[Lowfer] 8 ft Square Loop
Bill Ashlock
[email protected]
Thu, 31 Oct 2002 11:53:37 -0500
John, all:
>The best noise immunity would come from leaving it floating.
I tend to agree with John although I have tested this both ways and find no
difference - at least in my back woods (which may be totally differ from
your base environment).
Here's something to watch out for if there is no ground on the loop,
however: There can be capacity coupling from primary to secondary on the
transformer and this can give you some of the dreaded 'antenna effect' where
the loop begins acting as an E-field receptor and you start loosing the side
nulls and begin picking up additional noise. One solution to this problem
could be to use a small shield on the primary, connecting the shield to a
ground rod next to the loop. At least be sure the primary and secondary
windings are as far apart as possible.
The transformer coupled RX loop is about the same as the transformer
coupled, series connected, TX loop in reverse. Because of the super-low
impedance on the loop side you will ideally want to use only a single pass
through a ferrite core and about 20 turns on the secondary if you are
matching a coax. Could be a higher ratio if you are connecting to an
amplifier with a high Z input, as the more turns you have the higher will be
the signal level (within limits of course).
Bill A
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