Date: Fri, 1 Sep 2017 09:04:18 -0400
From: Markus Vester <markusvester@aol.com>
To: rsgb_lf_group@blacksheep.org
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Subject: VLF: E-field receivers in Todmorden
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Hi Paul,=20

this is strange... Wonder if it's really a difference in the noise level, o=
r maybe in the received signal level from the Alphas? Even though our anten=
nas are very much smaller than a wavelength, a bit of directivity due to en=
vironmental conditions (sloping terrain, wires in the vicinity, inhomogeneo=
us ground conductivity) would be conceivable. How far apart are the two ant=
ennas? Did you also try comparisons with signals from other directions?

Best 73,
Markus (DF6NM)

-----Urspr=C3=BCngliche Mitteilung-----=20
Von: Paul Nicholson <vlf0403@abelian.org>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Mi, 30. Aug 2017 19:51
Betreff: Re: VLF: Carrier on 4470.005 Hz! - EbNaut test


Stefan wrote:

 > I already thought about a new and longer message

I may have some interruptions to E-field reception here -
continuing to track down a 0.13 dB extra noise floor in the
new rx compared with the old.

Correlation of background noise is quite good, 97.6 % in a
3kHz bandwidth at 10kHz, after sferic removal. That means
most of the noise from the two rxs is the same - natural
background not system noise.

But the new rx is 0.13 dB higher, on average, than the old.
Every comparison run ranges 0.0 dB to about 0.3 dB, it's
pretty consistent.

Some recent readings on S/N of alpha at 11904.7619 Hz,
(each a 20 minute average):

 Old 37.27 dB, New 36.95 dB;
 Old 41.99 dB, New 41.86 dB;
 Old 41.95 dB, New 41.79 dB;

You see what I mean.

I've eliminated the sound cards, timing system and DSP,
isolating transformers and feeder, line drivers and the
filter stage before the line driver.

Now I'm at the output of the front-end and still the 0.13
dB remains. The front-end has been measured to death and is
well modeled. I'm beginning to wonder if there's something
wrong with the antenna, an extra source of noise from somewhere.

The old rx has just about had it, I can't expect it will last
another winter. New one should be better - not worse!

Well I have to get on with this mystery, so some interruptions.

--
Paul Nicholson
--
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<div style=3D"font-size:10pt;font-family:arial,helvetica,sans-serif;color:b=
lack;"><div style=3D"color: black; font-family: arial,helvetica,sans-serif;=
 font-size: 10pt;">Hi Paul, <br><br>this is strange... Wonder if it's reall=
y a difference in the noise level, or maybe in the received&nbsp;signal lev=
el from the Alphas? Even though our antennas are&nbsp;very much smaller tha=
n a wavelength, a bit of directivity due to environmental conditions (slopi=
ng terrain, wires in the vicinity, inhomogeneous ground conductivity) would=
 be conceivable. How far apart are the two antennas? Did you also try compa=
risons with&nbsp;signals from other directions?<br><br>Best 73,<br>Markus (=
DF6NM)<br><br>-----Urspr=C3=BCngliche Mitteilung----- <br>Von: Paul Nichols=
on &lt;vlf0403@abelian.org&gt;<br>An: rsgb_lf_group &lt;rsgb_lf_group@black=
sheep.org&gt;<br>Verschickt: Mi, 30. Aug 2017 19:51<br>Betreff: Re: VLF: Ca=
rrier on 4470.005 Hz! - EbNaut test<br><br></div><br>Stefan wrote:<br><br> =
&gt; I already thought about a new and longer message<br><br>I may have som=
e interruptions to E-field reception here -<br>continuing to track down a 0=
.13 dB extra noise floor in the<br>new rx compared with the old.<br><br>Cor=
relation of background noise is quite good, 97.6 % in a<br>3kHz bandwidth a=
t 10kHz, after sferic removal.  That means<br>most of the noise from the tw=
o rxs is the same - natural<br>background not system noise.<br><br>But the =
new rx is 0.13 dB higher, on average, than the old.<br>Every comparison run=
 ranges 0.0 dB to about 0.3 dB, it's<br>pretty consistent.<br><br>Some rece=
nt readings on S/N of alpha at 11904.7619 Hz,<br>(each a 20 minute average)=
:<br><br>  Old 37.27 dB, New 36.95 dB;<br>  Old 41.99 dB, New 41.86 dB;<br>=
  Old 41.95 dB, New 41.79 dB;<br><br>You see what I mean.<br><br>I've elimi=
nated the sound cards, timing system and DSP,<br>isolating transformers and=
 feeder, line drivers and the<br>filter stage before the line driver.<br><b=
r>Now I'm at the output of the front-end and still the 0.13<br>dB remains. =
  The front-end has been measured to death and is<br>well modeled. I'm begi=
nning to wonder if there's something<br>wrong with the antenna, an extra so=
urce of noise from somewhere.<br><br>The old rx has just about had it, I ca=
n't expect it will last<br>another winter.  New one should be better - not =
worse!<br><br>Well I have to get on with this mystery, so some interruption=
s.<br><br>--<br>Paul Nicholson<br>--<br><br></div>
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