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Message-ID: <268269.2794.qm@web28106.mail.ukl.yahoo.com>
Date: Tue, 4 Jan 2011 01:09:58 +0000 (GMT)
From: M0FMT <m0fmt@yahoo.co.uk>
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: Re: G3XIZ TX Monday 3 Jan
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Hi Jim

Many thanks for the fulsome reply.

I appreciate what you are saying , Shannon and the rest. However my machin=
e just=20
grinds to a stop when I try the set Spec lab how=A0I think it should be so=
 I was=20
suspecting that there was an issue of performance here.

And=A0I know my settings are not the best but the opportunity is only very=
 short=20
so once=A0I thought I had a stable set up I left it and was eventually rew=
arded.

I know its not very scientific but I had it in my bones I would get him to=
day.=20
Once again thanks for the info.
=A073 es GL petefmt=20


I support www.NotSpotTelecom.Com your community Telco / ISP.=20




________________________________
From: James Moritz <james.moritz@btopenworld.com>
To: rsgb_lf_group@blacksheep.org
Sent: Mon, 3 January, 2011 21:07:50
Subject: LF: Re: G3XIZ TX Monday 3 Jan

Dear Pete, LF Group,

Good to see you are getting some results... The equipment in use here was=
=20
nothing unusual - a "budget" Acer laptop abt 4 years old with internal sou=
nd=20
card, and the VLF loop and preamp, the schematic for which I posted=A0 som=
e time=20
ago. Probably the main difference between my spectrogram and the one from=
 M0FMT=20
is you appear to be using settings for relatively fast QRSS speeds; QRSS10=
 or=20
thereabouts. The pixels appear to have a resolution of about 100mHz, compa=
red to=20
the 1.5mHz I used. Using the narrower resolution increases the SNR by abou=
t=20
18dB, at least when averaged over the 600s period of the FFT. I am also us=
ing=20
the SpecLab hard limiter in conjunction with a 9kHz bandpass filter (which=
 could=20
alternatively be implemented in SpecLab instead of in the preamp, as I hav=
e it),=20
which reduces the contribution of QRN to the overall noise level by perhap=
s=20
several more dB. It looks like the noise level in both spectrograms is dom=
inated=20
by external noise, so there is little that can be done beyond this in term=
s of=20
equipment design to improve SNR.

In some cases, using a loop may give some advantage over a vertical, if th=
e=20
source of QRN is in a different direction from the wanted signal, but ofte=
n QRN=20
seems to originate from a wide area, so the sharp null of a loop is not=20
particularly effective. A definite advantage of small whip or loop antenna=
s over=20
bigger fixed wire antennas is that they can be moved around easily to find=
 a=20
location with minimum local QRM, whether this is different places around=
 your=20
home QTH, or going /P in the middle of a field well away from mains wiring=
 This=20
has brought a few more dBs improvement when I have done it in the past. In=
 both=20
cases, having a portable PC is also very helpful, since it can be operated=
=20
independently from the mains power, which helps to determine and/or elimin=
ate=20
this as a noise source.

Trying to receive weaker signals would require longer integration periods=
 with=20
even higher FFT resolution. The Acer laptop and its sound card are adequat=
e for=20
QRSS600/millihertz resolution as in this case, but for microhertz resoluti=
on,=20
higher short and long term frequency stability would be needed for both TX=
 and=20
RX.

Cheers, Jim Moritz
73 de M0BMU



----- Original Message ----- From: "M0FMT" <m0fmt@yahoo.co.uk>
To: <rsgb_lf_group@blacksheep.org>
Sent: Monday, January 03, 2011 4:11 PM
Subject: Re: LF: Re: VLF - G3XIZ TX Monday 3 Jan


Hi LF and Jim what pc are you running? Like processor speed and memory? Pl=
ease


     =20

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Content-Transfer-Encoding: quoted-printable

<html><head><style type=3D"text/css"><!-- DIV {margin:0px;} --></style></h=
ead><body><div style=3D"font-family:bookman old style, new york, times, se=
rif;font-size:10pt"><DIV style=3D"FONT-SIZE: 10pt; FONT-FAMILY: bookman ol=
d style, new york, times, serif">
<DIV></DIV>
<DIV>Hi Jim</DIV>
<DIV>&nbsp;</DIV>
<DIV>Many thanks for the fulsome reply.</DIV>
<DIV>&nbsp;</DIV>
<DIV>I appreciate what you are saying , Shannon and the rest. However my=
 machine just grinds to a stop when I try the set Spec lab how&nbsp;I thin=
k it should be so I was suspecting that there was an issue of performance=
 here.</DIV>
<DIV>&nbsp;</DIV>
<DIV>And&nbsp;I know my settings are not the best but the opportunity is=
 only very short so once&nbsp;I thought I had a stable set up I left it an=
d was eventually rewarded.</DIV>
<DIV>&nbsp;</DIV>
<DIV>I know its not very scientific but I had it in my bones I would get=
 him today. </DIV>
<DIV>Once again thanks for the info.<BR>&nbsp;</DIV>73 es GL petefmt=20
<DIV></DIV><BR><BR>
<DIV>I support www.NotSpotTelecom.Com your community Telco / ISP.=20
<DIV><BR></DIV>
<DIV style=3D"FONT-SIZE: 10pt; FONT-FAMILY: bookman old style, new york,=
 times, serif"><BR>
<DIV style=3D"FONT-SIZE: 13px; FONT-FAMILY: arial, helvetica, sans-serif">=
<FONT face=3DTahoma size=3D2>
<HR SIZE=3D1>
<B><SPAN style=3D"FONT-WEIGHT: bold">From:</SPAN></B> James Moritz &lt;jam=
es.moritz@btopenworld.com&gt;<BR><B><SPAN style=3D"FONT-WEIGHT: bold">To:<=
/SPAN></B> rsgb_lf_group@blacksheep.org<BR><B><SPAN style=3D"FONT-WEIGHT:=
 bold">Sent:</SPAN></B> Mon, 3 January, 2011 21:07:50<BR><B><SPAN style=3D=
"FONT-WEIGHT: bold">Subject:</SPAN></B> LF: Re: G3XIZ TX Monday 3 Jan<BR><=
/FONT><BR>Dear Pete, LF Group,<BR><BR>Good to see you are getting some res=
ults... The equipment in use here was nothing unusual - a "budget" Acer la=
ptop abt 4 years old with internal sound card, and the VLF loop and preamp=
, the schematic for which I posted&nbsp; some time ago. Probably the main=
 difference between my spectrogram and the one from M0FMT is you appear to=
 be using settings for relatively fast QRSS speeds; QRSS10 or thereabouts.=
 The pixels appear to have a resolution of about 100mHz, compared to the=
 1.5mHz I used. Using the narrower resolution increases the SNR by about=
 18dB, at least when
 averaged over the 600s period of the FFT. I am also using the SpecLab har=
d limiter in conjunction with a 9kHz bandpass filter (which could alternat=
ively be implemented in SpecLab instead of in the preamp, as I have it),=
 which reduces the contribution of QRN to the overall noise level by perha=
ps several more dB. It looks like the noise level in both spectrograms is=
 dominated by external noise, so there is little that can be done beyond=
 this in terms of equipment design to improve SNR.<BR><BR>In some cases,=
 using a loop may give some advantage over a vertical, if the source of QR=
N is in a different direction from the wanted signal, but often QRN seems=
 to originate from a wide area, so the sharp null of a loop is not particu=
larly effective. A definite advantage of small whip or loop antennas over=
 bigger fixed wire antennas is that they can be moved around easily to fin=
d a location with minimum local QRM, whether this is different places arou=
nd your home
 QTH, or going /P in the middle of a field well away from mains wiring Thi=
s has brought a few more dBs improvement when I have done it in the past.=
 In both cases, having a portable PC is also very helpful, since it can be=
 operated independently from the mains power, which helps to determine and=
/or eliminate this as a noise source.<BR><BR>Trying to receive weaker sign=
als would require longer integration periods with even higher FFT resoluti=
on. The Acer laptop and its sound card are adequate for QRSS600/millihertz=
 resolution as in this case, but for microhertz resolution, higher short=
 and long term frequency stability would be needed for both TX and RX.<BR>=
<BR>Cheers, Jim Moritz<BR>73 de M0BMU<BR><BR><BR><BR>----- Original Messag=
e ----- From: "M0FMT" &lt;<A href=3D"mailto:m0fmt@yahoo.co.uk" target=3D_b=
lank rel=3Dnofollow ymailto=3D"mailto:m0fmt@yahoo.co.uk">m0fmt@yahoo.co.uk=
</A>&gt;<BR>To: &lt;<A href=3D"mailto:rsgb_lf_group@blacksheep.org" target=
=3D_blank   rel=3Dnofollow ymailto=3D"mailto:rsgb_lf_group@blacksheep.org"=
>rsgb_lf_group@blacksheep.org</A>&gt;<BR>Sent: Monday, January 03, 2011 4:=
11 PM<BR>Subject: Re: LF: Re: VLF - G3XIZ TX Monday 3 Jan<BR><BR><BR>Hi LF=
 and Jim what pc are you running? Like processor speed and memory? Please<=
BR><BR><BR></DIV></DIV></DIV></DIV></div><br>



      </body></html>

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