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

To: [email protected]
Subject: AW: Re: VLF: E-field receivers in Todmorden
From: "Bernhard Wiesgickl (Asamnet)" <[email protected]>
Date: Sun, 03 Sep 2017 09:35:48 +0200
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Reply-to: [email protected]
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Hello Paul, 
I followed your reports about your disappointing results with a new low noise amplifier. I plan to build this amplifier:

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 <[email protected]>
Datum: 02.09.2017 8:43 (GMT+01:00)
An: [email protected]
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

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

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