Re: [IRCA] IRCA Loop update

[Nick Hall-Patch <nhp@xxxxxxxx>]

At 01:40 13/11/2005, you wrote:


> > My thinking on the toroid transformer was the pipe resistance was in the
> > range of 0.1 ohms; a match to 50 ohms coax would be the square root of
> > 50/0.1 or 500, which rounded off gave a convenient 22 turns for the
> > secondary winding on the toroid. I used #24 gauge enamel wire, with a BNC
> > connector attached.
>
>Ah.  There's a problem.  The second loop I built used 24 turns of #16.  Had
>very little output voltage.  I unwound it down to 6 turns and it was good.
>Later I tried four turns of #16 and it was even better.  I have not tried
>either three or five turns to see where the optimum point is.  Rewind the
>output link to four turns of #16 or heavier wire and it'll make a big
>difference.  And no, I have no idea why.  All I know is that it just works.
>

Steve and Craig...

I don't understand this either, but have found that untuned wire loops have 
an impedance not far off 50 ohms, judging by signal strength delivered to 
the receiver and the turns ratio used on the matching / isolating 
transformer.   The lower RF resistance of the copper pipe loop may give it 
a somewhat lower impedance....

best wishes,

Nick



>*************************************************************************

Nick Hall-Patch
Victoria, B.C.
Canada

**************************************************************************** 

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