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LF: QRM - Other

from [hvanesce] [Permanent Link][Original]
To: <[email protected]>
Subject: LF: QRM - Other
From: <[email protected]>
Date: Thu, 14 Feb 2019 15:50:15 -0500
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This popular item doesn’t seem particularly friendly for ULF-VLF; 40 to 76 turns wrapped around the home’s water main pipe, ~ 2 amps out, sweeping 1 kHz to 20 kHz every 50 milliseconds.

https://www.scaleblaster.com/wp-content/uploads/docs/spec-max.pdf

https://www.scaleblaster.com/wp-content/uploads/docs/installation-max.pdf

which would seem to give roughly 40 fT at 100m at for the specified 70 turns on 4 cm water main, not counting eddy currents in the copper pipe.

Not sure how current varies* with frequency in these devices, or how rectangular the current waveform is.

  * (guessing current varies as 1/f, which would mean roughly 30 fT at 50m at 10 kHz)

 

A commercial unit provides 10A-40A into a 200uH coil around the water main (less current into the nominal 1 mH coil):

https://www.scaleblaster.com/wp-content/uploads/2016/08/SB-4000-clm276.pdf

https://www.scaleblaster.com/wp-content/uploads/2016/07/Sb1200-SB4000-Install-Operations-Manual.pdf

which would seem to give roughly 10 fT at 1 km for the specified 7 turns on 106 cm water main.

 

- Jim AA5BW  

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