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: [email protected]
[mailto:[email protected]] On Behalf Of Paul Nicholson
Sent: Wednesday, November 29, 2017 12:12 PM
To: [email protected]
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
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