From: <hvanesce@comcast.net>
To: <rsgb_lf_group@blacksheep.org>
References: <4d96a9d4-5f22-7650-872b-6344e9aea8e3@abelian.org> <00f901d36646$feda4e60$fc8eeb20$@comcast.net> <085dd850-9c10-16a0-70ef-fb2de079ffb8@abelian.org> <023201d367cf$8a5761b0$9f062510$@comcast.net> <b22c25ae-1b76-f1bb-1e54-9ecc8143e7c8@abelian.org>
In-Reply-To: <b22c25ae-1b76-f1bb-1e54-9ecc8143e7c8@abelian.org>
Date: Wed, 29 Nov 2017 14:25:58 -0500
Message-ID: <03ae01d36947$e35db4c0$aa191e40$@comcast.net>
MIME-Version: 1.0
Thread-Index: AQMcfBPTxY+k5qd6rWysCs3Lx7yy3QGHY7qfAYgyFwwBFArxWgIuAFB6oGcGCOA=
Content-Language: en-us
Subject: RE: LF: RE: Todmorden receiver
Content-Type: text/plain;
	charset="utf-8"
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
Content-Transfer-Encoding: 8bit

Hello Paul,

By noise from light do you mean shot noise from the average solar flux? I tried a quick calculation yielding < 1 nV/rt-Hz, and I guessed that your noise voltage density is more than 10x that. Did I calculate incorrectly or are you perhaps thinking of a different transduction mechanism? Very interesting in any case. I wouldn't have thought of noise from light and it's intriguing to think about how active nature is at your receiver's equivalent noise field strength.    

73,

Jim AA5BW  


-----Original Message-----
From: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Paul Nicholson
Sent: Wednesday, November 29, 2017 12:12 PM
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: RE: Todmorden receiver


The re-built E-field rx was put outside this afternoon for a on-air trial.

Pre-amp inside the antenna tube

  http://abelian.org/vlf/tmp/171129a.jpg

I'm a bit worried about noise from light getting into the tube - the plastic lets a bit of light through.  I'll probably have to fit an opaque liner.

Here's the power supply, filter and line driver

  http://abelian.org/vlf/tmp/171129c.jpg

I just got finished at dusk

  http://abelian.org/vlf/tmp/171129d.jpg

The antenna looks remote but there's still 140mV RMS of 50Hz on it.  This doesn't come from the house, or even the overhead power lines to the house, but from further away.

I'm using a metal support pole and guys - hopefully that means the calibration won't change so much between wet and dry conditions.

Here's the spectrum

  http://abelian.org/vlf/tmp/171129e.gif

It seems to be working well, no intermod.  The gain is a little too high, overall x30 voltage gain from antenna to soundcard input.  I'll have to drop that to about x15 tomorrow.  It really doesn't need much gain with a 2m antenna tube 2m off the ground.

--
Paul Nicholson
--