AW: Re: VLF: E-field receivers in Todmorden

["Bernhard Wiesgickl (Asamnet)" <bernhard.wiesgickl@asamnet.net>]

Hello Paul, 

I followed your reports about your disappointing results with a new low noise amplifier. I plan to build this amplifier:

http://dg4rbf.lima-city.de/Ultra%20Low%20Noise%20AMP%20V1.7f%20_WebSeite.pdf

This LNA is built with 4 parallel FETs in front of a low noise OP-Amp and has an

equivalent input voltage noise density of 400 nVeff/SQRT (Hz). 

Please your opinion about this concept?

73s de Bernd, DF9RB

Von Samsung-Tablet gesendet

-------- Ursprüngliche Nachricht --------
Von: Paul Nicholson <vlf0403@abelian.org> 
Datum: 02.09.2017  8:43  (GMT+01:00) 
An: rsgb_lf_group@blacksheep.org 
Betreff: Re: VLF: E-field receivers in Todmorden 
 


Markus wrote:

 > maybe in the received signal level from the Alphas?
 > ... a bit of directivity due to environmental conditions

I wonder.

One curious fact supporting this is the noise blanker drop
factor.  This is the proportion of time the blanker is active.

The drop factor is always a bit higher on the new rx than
the old when I run the two signals through independent sferic
blankers.

The blanking threshold is set relative to the noise floor,
which is tracked by an asymmetric moving average.  The new rx
must have a lower threshold to have a higher blanking factor,
therefore vtblank is finding a lower floor (relative to the
sferics) on the new rx compared with the old.

So, the E-field probes are not quite omni-directional perhaps?

I need to look at more signals, from different directions,
to build a picture.

--
Paul Nicholson
--