Message-ID: <4FC39CF3.7020701@legal-medicine.de>
Date: Mon, 28 May 2012 17:42:43 +0200
From: pws <pws@legal-medicine.de>
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To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
Subject: LF: VLF/LF-Preamp
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Hi,

After all those meta-discussions here's a more serious problem:

I'm playing around with a new e-field probe based on the INA111.
http://www.ti.com/product/ina111

Schematic: http://www.df3lp.de/misc/rx/INA111_preamp.png

It's working fine and the local interferences are lower compared to
my old non-balanced design running here on balcony. That was the goal.

Amplification is quite enough to drive a M-Audio audiophile 192 soundcard.
There's a second transformer (1:4) at the af-inputs. The coupling
capacitance of those transformers are below 10pF each.

I'm using the shields of a thin double coaxial line for bringing up
the supply voltage. The voltage splitter is located at the far end inside 
the small amplifier box.

The problem is that I'm observing to a lot of interferences/microphonics
"from behind" when touching the battery located inside the house.

???

Peter, df3lp