Delivered-To: daveyxm@virginmedia.com
Received: by 10.50.96.198 with SMTP id du6csp72833igb;
Thu, 5 Dec 2013 16:35:25 -0800 (PST)
X-Received: by 10.194.11.38 with SMTP id n6mr474763wjb.25.1386290124908;
Thu, 05 Dec 2013 16:35:24 -0800 (PST)
Return-Path: <owner-rsgb_lf_group@blacksheep.org>
Received: from post.thorcom.com (post.thorcom.com. [195.171.43.25])
by mx.google.com with ESMTP id k1si214553wiy.70.2013.12.05.16.35.24
for <daveyxm@virginmedia.com>;
Thu, 05 Dec 2013 16:35:24 -0800 (PST)
Received-SPF: neutral (google.com: 195.171.43.25 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org) client-ip=195.171.43.25;
Authentication-Results: mx.google.com;
spf=neutral (google.com: 195.171.43.25 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org) smtp.mail=owner-rsgb_lf_group@blacksheep.org;
dkim=fail header.i=@mx.aol.com
Received: from majordom by post.thorcom.com with local (Exim 4.14)
id 1Voio8-00021z-4a
for rs_out_1@blacksheep.org; Thu, 05 Dec 2013 23:58:12 +0000
Received: from [195.171.43.32] (helo=relay1.thorcom.net)
by post.thorcom.com with esmtp (Exim 4.14)
id 1Voio7-00021q-4v
for rsgb_lf_group@blacksheep.org; Thu, 05 Dec 2013 23:58:11 +0000
Received: from omr-d06.mx.aol.com ([205.188.109.203])
by relay1.thorcom.net with esmtps (TLSv1:AES256-SHA:256)
(Exim 4.77)
(envelope-from <markusvester@aol.com>)
id 1Voio3-00016L-2U
for rsgb_lf_group@blacksheep.org; Thu, 05 Dec 2013 23:58:10 +0000
Received: from mtaout-da03.r1000.mx.aol.com (mtaout-da03.r1000.mx.aol.com [172.29.51.131])
by omr-d06.mx.aol.com (Outbound Mail Relay) with ESMTP id 40CBF7016A306;
Thu, 5 Dec 2013 18:58:03 -0500 (EST)
Received: from White (95-91-238-155-dynip.superkabel.de [95.91.238.155])
by mtaout-da03.r1000.mx.aol.com (MUA/Third Party Client Interface) with ESMTPA id 1B1A0E0000B2;
Thu, 5 Dec 2013 18:57:59 -0500 (EST)
Message-ID: <5FBCFC1F826C434E94FBACF3D24866DB@White>
From: "Markus Vester" <markusvester@aol.com>
To: <rsgb_lf_group@blacksheep.org>,
<rsgb_lf_group@yahoogroups.co.uk>
Date: Fri, 6 Dec 2013 00:57:47 +0100
MIME-Version: 1.0
X-Priority: 3
X-MSMail-Priority: Normal
Importance: Normal
X-Mailer: Microsoft Windows Live Mail 12.0.1606
X-MimeOLE: Produced By Microsoft MimeOLE V12.0.1606
x-aol-global-disposition: G
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com;
s=20121107; t=1386287883;
bh=GRU95WPe/VmVOFWK6xyO5FMMNjsAIGWbFMZMgOVTyOI=;
h=From:To:Subject:Message-ID:Date:MIME-Version:Content-Type;
b=hwXFuyNkOs+rxl4tDxNMsu8yI7QcmgVJyYa1kcUPw6JIDACLDUPwJiOLAUgjBfBHf
s6rKBBxXIDXLcC0A5sj6Rh3mDwG/YZ2eAkRhcE7/MNvJ+7aLjF39+BZEOHAb1HcQpG
1krxMtd/8wBPjWvuu34Z63QmzMVRrRXLwM9+jaFQ=
x-aol-sid: 3039ac1d338352a1130761cf
X-AOL-IP: 95.91.238.155
X-Spam-Score: 0.0 (/)
X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has
identified this incoming email as possible spam. The original message
has been attached to this so you can view it (if it isn't spam) or label
similar future email. If you have any questions, see
the administrator of that system for details.
Content preview: I think I have found a way to eliminate interference from
the DCF77 pseudonoise modulation in 74.55 kHz spectrograms. As explained before,
the problem is that the phase-modulating PRN sequence carries the timecode
of DCF77, sending an inverted sequence with every "1" bit. Thus what would
otherwise be a comb spectrum of discrete 1 Hz lines is being spread out,
contaminating the space between the lines with noise-like patterns. [...]
Content analysis details: (0.0 points, 5.0 required)
pts rule name description
---- ---------------------- --------------------------------------------------
-0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no
trust
[205.188.109.203 listed in list.dnswl.org]
0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider
(markusvester[at]aol.com)
-0.0 SPF_PASS SPF: sender matches SPF record
-0.0 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain
0.0 HTML_MESSAGE BODY: HTML included in message
0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid
X-Scan-Signature: 25586c7917467b5c110472bf48f6f4f3
Subject: LF: Cleaning up DCF77 junk around 74.55 kHz
Content-Type: multipart/alternative;
boundary="----=_NextPart_000_002C_01CEF21E.2DCB4540"
X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com
X-Spam-Level:
X-Spam-Status: No, hits=0.6 required=5.0 tests=HTML_40_50,HTML_MESSAGE,
MISSING_OUTLOOK_NAME autolearn=no version=2.63
X-SA-Exim-Scanned: Yes
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
X-Listname: rsgb_lf_group
X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org
X-SA-Exim-Scanned: No; SAEximRunCond expanded to false
Status: O
X-Status:
X-Keywords:
X-UID: 375
Dies ist eine mehrteilige Nachricht im MIME-Format.
------=_NextPart_000_002C_01CEF21E.2DCB4540
Content-Type: text/plain;
charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
I think I have found a way to eliminate interference from the DCF77 =
pseudonoise modulation in 74.55 kHz spectrograms.
As explained before, the problem is that the phase-modulating PRN =
sequence carries the timecode of DCF77, sending an inverted sequence =
with every "1" bit. Thus what would otherwise be a comb spectrum of =
discrete 1 Hz lines is being spread out, contaminating the space between =
the lines with noise-like patterns.
The idea is now to unspread the lines, based on the known time bits, =
which are also communicated by prolonged second gaps (0.2 s for a "1" =
bit). Multiplying the 74.5 kHz stream by the 1, 1, -1... data will fold =
all the interference energy back to discrete 1 Hz multiples. These can =
then be notched out. Finally the despeading has to be undone with the =
same data, restoring the desired spectral features (amateur signals or =
Loran lines), but without the interference.=20
Example results and zipped MathCad and data files are in=20
df6nm.bplaced.net/LF/74kHz/DCF77_PRN_cancellation/=20
and a comparison of unprocessed and processed spectrograms from the =
night November 7 / 8:
df6nm.bplaced.net/LF/74kHz/DCF77_PRN_cancellation/sp_2e.png =
(spectrogram as received),
df6nm.bplaced.net/LF/74kHz/DCF77_PRN_cancellation/spr_2e.png =
(spectrogram with DCF77 sidebands removed).
Unfortunately there was no signal from Bob or Dex during the night of =
the recording. All you can see are a few Loran lines, eg. on 74556.6076, =
74550.5868, 74549.9400 Hz. I want to try this again, but not today as =
the big antenna which is needed for 74 kHz is currently retracted due to =
heavy winds.
For anyone interested in the postprocessing, here are the steps in =
detail:
1. Using SpecLab, VAC and SndInput, I took a narrowband IQ recording, =
with decimation of 768 down to 15.625 Hz samplerate. There are two audio =
channels, one centered on the desired band around 74.550 kHz, and the =
other on 77.5 kHz for reference. In the example, the overnight recording =
started 13-11-07 16:38, and ended next morning 6:24. The 6 MB .tmp file =
was preceded by a dummy .bmp header to be able to read it with the old =
MathCad version 6.0.=20
2. In the MathCad script, the second dips were identified and the bits =
extracted from therir duration. The first 15 bits which carry encrypted =
weather information are not included in the phase modulation, and have =
to be substituted by a fixed 111111111100000 sequence. In principle, the =
time telegrams are completely predictable (except possible leap =
seconds), so with accurate time information one could do without the =
77.5 kHz channel and the bit decoding.
3. The time domain data is split into overlapping 2048 sample chunks, =
allowing to generate spectrograms at 7.63 mHz resolution. For each =
chunk, a windowed FFT is generated, leading to the unprocessed =
spectrogram (sp_2e.png)
4. In time domain, the samples during each second with a preceding "1" =
bit are multiplied by -1, despreading the interference.=20
5. These data chunks are also Fourier transformed, producing spectra =
with discrete 1 Hz peaks.=20
6. The bins on and near integer Hz frequencies are nulled, notching out =
the interference.
7. The data is brought back to time domain with an inverse FFT.
8. The polarity inversion of the "1" periods is undone, applying the =
same procedure as in step 4 again.
9. Finally data is Fourier transformed again, producing the clean =
spectrogram result (spr_2e.png).
Best 73,
Markus (DF6NM)
From: Markus Vester=20
Sent: Tuesday, October 01, 2013 7:35 AM
To: rsgb_lf_group@blacksheep.org=20
Subject: Re: LF: 74.550kHz Sep 29/30
Here are clearer shots of the DCF77 sidebands from the morning:
http://dl.dropboxusercontent.com/u/26404526/dcf77_prn_sidebands_131001_06=
05.png
http://dl.dropboxusercontent.com/u/26404526/74k_131001_0600.png
Notes:
- the RX antenna is resonant around 75 kHz, which emphasizes the PRN =
sidebands below the DCF77 carrier. The fifth and sixth lobe are still =
visible. In reality, the upper sidebands are slightly stronger. This is =
probably due to an offset (or a 75 kHz notch) in the transmitter antenna =
matching, which happens to help us now.
- the Swiss time signal HBG on 75 kHz is no longer on air.
- there is an RTTY signal at 73.6 kHz which could be CFH.=20
- the 1 Hz lines are surrounded by a somewhat regular fine structure, =
consisting of 16.6 mHz spaced sub-lines. This is probably due to parts =
of the BCD timecode and weather information data which are repeating or =
similar in consecutive minutes.
Best 73,
Markus (DF6NM)
From: Markus Vester=20
Sent: Monday, September 30, 2013 11:26 PM
To: rsgb_lf_group@blacksheep.org=20
Subject: Re: LF: 74.550kHz Sep 29/30
Hi Bob, LF,
last night my improvised grabber =
http://dl.dropboxusercontent.com/u/26404526/df6nm_74kHz.jpg indeed =
showed weak and slightly fuzzy traces on both your QRG's, and on all =
other integer Hz frequencies as well.=20
These are presumably artifacts from DCF77 which is only about 160 km =
from here. In addition to the well known AM timecode, it also carries =
pseudorandom phase modulation, which has been proposed in the 80ies to =
provide higher resolution timing (albeit orders of magnitude worse than =
Loran or GPS). The resulting sidebands extend a couple of kHz on either =
side of the carrier, with pronounced minima around multiples of the chip =
rate 77500/120 =3D 645.833 Hz, see=20
http://www.ptb.de/cms/fileadmin/internet/fachabteilungen/abteilung_4/4.4_=
zeit_und_frequenz/pdf/5_1988_Hetzel_-_Proc_EFTF_88.pdf (page 358). The =
same code sequence is repeated every second, so in theory the spectrum =
would consist of sharp 1 Hz spaced lines. However, additionally the sign =
of the sequence is alternated with the disseminated timecode bits, =
producing some widening or "fuzzyness" of the lines.
Attached is a spectrogram which was taken tonight on the resonant =
antenna. Between statics, you can still see the fourth sideband lobe =
which is centered near 74.6 kHz. The spectral gaps are on=20
74916.666 Hz,=20
74270.833 Hz,=20
73625.000 Hz,=20
with small and sharp central lines, presumably caused by slight =
inbalances or nonlinearities in the transmitter.
By these criteria, if you have the choice I would recommend to operate =
somewhere near these gaps, but not exactly in their middle, and also =
preferably not exactly on integer Hz frequencies ;-)
Best 73,
Markus (DF6NM)
...
------=_NextPart_000_002C_01CEF21E.2DCB4540
Content-Type: text/html;
charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META content=3Dtext/html;charset=3Diso-8859-1 =
http-equiv=3DContent-Type>
<STYLE><!--
.hmmessage P
{
margin:0px;
padding:0px
}
body.hmmessage
{
font-size: 12pt;
font-family:Calibri
}
--></STYLE>
<META name=3DGENERATOR content=3D"MSHTML 8.00.6001.23536"></HEAD>
<BODY style=3D"PADDING-LEFT: 10px; PADDING-RIGHT: 10px; PADDING-TOP: =
15px"=20
id=3DMailContainerBody class=3Dhmmessage leftMargin=3D0 topMargin=3D0 =
bgColor=3D#ffffff=20
CanvasTabStop=3D"true" name=3D"Compose message area">
<DIV><FONT size=3D2 face=3DArial>I think I have found a way=20
to eliminate interference from the DCF77 pseudonoise =
modulation=20
in 74.55 kHz spectrograms.</FONT></DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial><FONT =
face=3DArial></FONT><FONT=20
face=3DArial></FONT><FONT face=3DArial></FONT><FONT=20
face=3DArial></FONT></FONT> </DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial>As explained before, =
the problem=20
is that the phase-modulating PRN sequence carries the timecode =
of=20
DCF77, sending an inverted sequence with every "1" bit.=20
Thus what would otherwise be a comb spectrum of discrete 1 Hz =
lines is=20
being spread out, contaminating the space between the lines with =
noise-like=20
patterns.</FONT></DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial><FONT=20
face=3DArial></FONT></FONT> </DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial>The idea is now =
to=20
unspread the lines, based on the known time bits, which =
are also=20
communicated by prolonged second gaps (0.2 s for a "1" =
bit). Multiplying=20
the 74.5 kHz stream by the 1, 1, -1... data =
will fold all=20
the interference energy back to discrete 1 Hz multiples.=20
These can then be notched out. Finally the despeading has to =
be undone=20
with the same data, restoring the desired spectral features =
(amateur=20
signals or Loran lines), but without the =
interference. </FONT></DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial><FONT=20
face=3DArial></FONT></FONT> </DIV><FONT face=3DArial>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial>Example results and =
zipped=20
MathCad and data files are in </FONT></DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT=20
face=3DArial> df6nm.bplaced.net/LF/74kHz/DCF77_PRN_cancellation/&nbs=
p;</FONT></DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial>and a =
comparison of=20
unprocessed and processed spectrograms from the night November 7 /=20
8:</FONT></DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT=20
face=3DArial> df6nm.bplaced.net/LF/74kHz/DCF77_PRN_cancellation/sp_2=
e.png=20
(spectrogram as received),</FONT></DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT=20
face=3DArial> df6nm.bplaced.net/LF/74kHz/DCF77_PRN_cancellation/spr_=
2e.png=20
(spectrogram with DCF77 sidebands removed).</FONT></DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial><FONT=20
face=3DArial></FONT></FONT> </DIV></FONT>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial>Unfortunately there =
was no=20
signal from Bob or Dex during the night of the recording. All you can =
see are a=20
few Loran lines, eg. on <FONT size=3D2>74556.6076, </FONT><FONT =
size=3D2><FONT=20
size=3D2>74550.5868, </FONT>74549.9400 Hz.</FONT><FONT =
size=3D2> </FONT>I want=20
to try this again, but not today as the big antenna which is needed for =
74 kHz=20
is currently retracted due to heavy winds.</FONT></DIV>
<DIV><FONT face=3DArial><FONT size=3D2><FONT=20
face=3DArial></FONT></FONT></FONT> </DIV>
<DIV><FONT size=3D2 face=3DArial>For anyone interested in=20
the postprocessing, here are the steps in detail:</FONT></DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial><FONT=20
face=3DArial></FONT></FONT> </DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial>1. Using=20
SpecLab, VAC and SndInput, I took a narrowband IQ =
recording,=20
with decimation of 768 down to 15.625 Hz =
samplerate. There=20
are two audio channels, one centered on the desired band around 74.550 =
kHz, and=20
the other on 77.5 kHz for reference. In the example, the =
overnight=20
recording started 13-11-07 16:38, and ended next =
morning=20
6:24. The 6 MB .tmp file was preceded by a dummy .bmp=20
header to be able to read it with the old =
MathCad=20
version 6.0. </FONT></DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial><FONT=20
face=3DArial></FONT></FONT> </DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial>2. In the MathCad =
script, the=20
second dips were identified and the bits extracted from therir duration. =
The=20
first 15 bits which carry encrypted weather information are not included =
in the=20
phase modulation, and have to be substituted by a fixed=20
111111111100000 sequence. In principle, the time telegrams are =
completely=20
predictable (except possible leap seconds), so with accurate time =
information=20
one could do without the 77.5 kHz channel and the bit=20
decoding.</FONT></DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial><FONT=20
face=3DArial></FONT></FONT> </DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial>3. The time domain =
data=20
is split into overlapping 2048 sample chunks, allowing to generate=20
spectrograms at 7.63 mHz resolution. For each chunk, a windowed FFT is=20
generated, leading to the unprocessed spectrogram =
(sp_2e.png)</FONT></DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial></FONT> </DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial>4. In time domain,=20
the samples during each second with a preceding "1" bit are =
multiplied=20
by -1, despreading the interference. </FONT></DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial><FONT=20
face=3DArial></FONT></FONT> </DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial>5. These data =
chunks=20
are also Fourier transformed, producing spectra with discrete 1 Hz =
peaks.=20
</FONT></DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial><FONT=20
face=3DArial></FONT></FONT> </DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial>6. =
The bins on and=20
near integer Hz frequencies are nulled, notching out the=20
interference.</FONT></DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial><FONT=20
face=3DArial></FONT></FONT> </DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial>7. The data =
is brought back=20
to time domain with an inverse FFT.</FONT></DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial><FONT=20
face=3DArial></FONT></FONT> </DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial>8. The polarity =
inversion=20
of the "1" periods is undone, applying the same procedure as in =
step 4=20
again.</FONT></DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial><FONT=20
face=3DArial></FONT></FONT> </DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial>9. Finally data =
is Fourier=20
transformed again, producing the clean spectrogram result=20
(spr_2e.png).</FONT></DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial><FONT=20
face=3DArial></FONT></FONT> </DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial>Best =
73,</FONT></DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial>Markus =
(DF6NM)</FONT></DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial><FONT=20
face=3DArial></FONT></FONT> </DIV>
<DIV><FONT face=3DArial><FONT size=3D2><FONT face=3DArial><FONT=20
size=3D2></FONT></FONT></FONT> </DIV>
<DIV style=3D"FONT: 10pt Tahoma"><FONT face=3DArial></FONT><FONT=20
face=3DArial></FONT><FONT face=3DArial></FONT><FONT =
face=3DArial></FONT><FONT=20
face=3DArial></FONT><FONT face=3DArial><BR></FONT></DIV></FONT>
<DIV style=3D"FONT: 10pt Tahoma; font-color: black"><FONT =
face=3DArial><B>From:</B>=20
</FONT><A title=3Dmarkusvester@aol.com =
href=3D"mailto:markusvester@aol.com"><FONT=20
face=3DArial>Markus Vester</FONT></A><FONT face=3DArial> </FONT></DIV>
<DIV><FONT face=3DArial><FONT size=3D2><B>Sent:</B> Tuesday, October 01, =
2013 7:35=20
AM</FONT></FONT></DIV>
<DIV><FONT face=3DArial><FONT size=3D2><B>To:</B> </FONT></FONT><A=20
title=3Drsgb_lf_group@blacksheep.org=20
href=3D"mailto:rsgb_lf_group@blacksheep.org"><FONT size=3D2=20
face=3DArial>rsgb_lf_group@blacksheep.org</FONT></A><FONT size=3D2 =
face=3DArial>=20
</FONT></DIV>
<DIV><FONT face=3DArial><FONT size=3D2><B>Subject:</B> Re: LF: 74.550kHz =
Sep=20
29/30</FONT></FONT></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT><FONT size=3D2 =
face=3DArial></FONT><FONT size=3D2=20
face=3DArial></FONT><FONT size=3D2 face=3DArial></FONT><FONT size=3D2=20
face=3DArial></FONT><FONT size=3D2 face=3DArial></FONT><FONT size=3D2=20
face=3DArial></FONT><FONT size=3D2 face=3DArial></FONT><FONT size=3D2=20
face=3DArial></FONT><FONT size=3D2 face=3DArial></FONT><FONT size=3D2=20
face=3DArial></FONT><FONT size=3D2 face=3DArial></FONT><FONT size=3D2=20
face=3DArial><BR></FONT></DIV>
<DIV><FONT size=3D2 face=3DArial>Here are clearer shots of the DCF77=20
sidebands from the morning:</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial><A=20
title=3D"http://dl.dropboxusercontent.com/u/26404526/dcf77_prn_sidebands_=
131001_0605.png STRG + Klicken, um Verkn=FCpfung zu folgen"=20
href=3D"http://dl.dropboxusercontent.com/u/26404526/dcf77_prn_sidebands_1=
31001_0605.png">http://dl.dropboxusercontent.com/u/26404526/dcf77_prn_sid=
ebands_131001_0605.png</A></FONT></DIV>
<DIV><FONT size=3D2 face=3DArial><A=20
title=3D"http://dl.dropboxusercontent.com/u/26404526/74k_131001_0600.png&=
#10;STRG + Klicken, um Verkn=FCpfung zu folgen"=20
href=3D"http://dl.dropboxusercontent.com/u/26404526/74k_131001_0600.png">=
http://dl.dropboxusercontent.com/u/26404526/74k_131001_0600.png</A></FONT=
></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT> </DIV>
<DIV><FONT size=3D2 face=3DArial>Notes:</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial>- the RX antenna is =
resonant around 75 kHz,=20
which emphasizes the PRN sidebands below the DCF77 carrier. The =
fifth and=20
sixth lobe are still visible. In reality, the upper sidebands are =
slightly=20
stronger. This is probably due to an offset (or a 75 kHz notch) in =
the=20
transmitter antenna matching, which happens to help us =
now.</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial>- the Swiss time signal HBG on 75 kHz =
is no=20
longer on air.</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial>- there is an RTTY signal at 73.6 kHz =
which=20
could be CFH. </FONT></DIV>
<DIV><FONT size=3D2 face=3DArial>- the 1 Hz lines are surrounded by =
a somewhat=20
regular fine structure, consisting of 16.6 mHz spaced sub-lines. =
This is=20
probably due to parts of the BCD timecode =
and weather=20
information data which are repeating or similar in consecutive=20
minutes.</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT> </DIV>
<DIV><FONT size=3D2 face=3DArial>Best 73,</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial>Markus (DF6NM)</FONT></DIV>
<DIV><FONT face=3DArial></FONT><FONT face=3DArial></FONT><FONT=20
face=3DArial></FONT><FONT size=3D2 face=3DArial><BR></FONT></DIV>
<DIV style=3D"FONT: 10pt Tahoma; font-color: black"><FONT =
face=3DArial><B>From:</B>=20
</FONT><A=20
title=3D"mailto:markusvester@aol.com STRG + Klicken, um =
Verkn=FCpfung zu folgen"=20
href=3D"mailto:markusvester@aol.com"><FONT=20
title=3D"mailto:markusvester@aol.com STRG + Klicken, um =
Verkn=FCpfung zu folgen"=20
face=3DArial>Markus Vester</FONT></A><FONT face=3DArial> </FONT></DIV>
<DIV><FONT face=3DArial><FONT size=3D2><B>Sent:</B> Monday, September =
30, 2013 11:26=20
PM</FONT></FONT></DIV>
<DIV><FONT face=3DArial><FONT size=3D2><B>To:</B> </FONT></FONT><A=20
title=3D"mailto:rsgb_lf_group@blacksheep.org STRG + Klicken, um =
Verkn=FCpfung zu folgen"=20
href=3D"mailto:rsgb_lf_group@blacksheep.org"><FONT=20
title=3D"mailto:rsgb_lf_group@blacksheep.org STRG + Klicken, um =
Verkn=FCpfung zu folgen"=20
size=3D2 face=3DArial>rsgb_lf_group@blacksheep.org</FONT></A><FONT =
size=3D2=20
face=3DArial> </FONT></DIV>
<DIV><FONT face=3DArial><FONT size=3D2><B>Subject:</B> Re: LF: 74.550kHz =
Sep=20
29/30</FONT></FONT></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT><FONT size=3D2 =
face=3DArial></FONT><FONT size=3D2=20
face=3DArial><BR></FONT></DIV>
<DIV><FONT size=3D2 face=3DArial>Hi Bob, LF,</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT> </DIV>
<DIV><FONT size=3D2 face=3DArial>last night my improvised =
grabber </FONT><A=20
title=3D"http://dl.dropboxusercontent.com/u/26404526/df6nm_74kHz.jpg =
STRG + Klicken, um Verkn=FCpfung zu folgen"=20
href=3D"http://dl.dropboxusercontent.com/u/26404526/df6nm_74kHz.jpg"><FON=
T=20
title=3D"http://dl.dropboxusercontent.com/u/26404526/df6nm_74kHz.jpg =
STRG + Klicken, um Verkn=FCpfung zu folgen"=20
size=3D2=20
face=3DArial>http://dl.dropboxusercontent.com/u/26404526/df6nm_74kHz.jpg<=
/FONT></A><FONT=20
size=3D2 face=3DArial> indeed showed weak and slightly fuzzy traces =
on both=20
your QRG's, and on all other integer Hz frequencies as well. =
</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT> </DIV>
<DIV><FONT size=3D2 face=3DArial>These are presumably artifacts from =
DCF77 which is=20
only about 160 km from here. In addition to the well known=20
AM timecode, it also carries pseudorandom phase =
modulation,=20
which has been proposed in the 80ies to provide higher resolution =
timing=20
(albeit orders of magnitude worse than Loran or GPS). The resulting =
sidebands=20
extend a couple of kHz on either side of the carrier, with pronounced =
minima=20
around multiples of the chip rate 77500/120 =3D 645.833 Hz, see =
</FONT></DIV>
<DIV><A=20
title=3D"http://www.ptb.de/cms/fileadmin/internet/fachabteilungen/abteilu=
ng_4/4.4_zeit_und_frequenz/pdf/5_1988_Hetzel_-_Proc_EFTF_88.pdf STRG =
+ Klicken, um Verkn=FCpfung zu folgen"=20
href=3D"http://www.ptb.de/cms/fileadmin/internet/fachabteilungen/abteilun=
g_4/4.4_zeit_und_frequenz/pdf/5_1988_Hetzel_-_Proc_EFTF_88.pdf"><FONT=20
title=3D"http://www.ptb.de/cms/fileadmin/internet/fachabteilungen/abteilu=
ng_4/4.4_zeit_und_frequenz/pdf/5_1988_Hetzel_-_Proc_EFTF_88.pdf STRG =
+ Klicken, um Verkn=FCpfung zu folgen"=20
size=3D2=20
face=3DArial>http://www.ptb.de/cms/fileadmin/internet/fachabteilungen/abt=
eilung_4/4.4_zeit_und_frequenz/pdf/5_1988_Hetzel_-_Proc_EFTF_88.pdf</FONT=
></A><FONT=20
size=3D2 face=3DArial> (page 358). The same code sequence is =
repeated every=20
second, so in theory the spectrum would consist of sharp 1 Hz spaced =
lines.=20
However, additionally the sign of the sequence is alternated with =
the=20
disseminated timecode bits, producing some widening or "fuzzyness" =
of the=20
lines.</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT> </DIV>
<DIV><FONT size=3D2 face=3DArial>Attached is a spectrogram which =
was taken=20
tonight on the resonant antenna. Between statics, you =
can still=20
see the fourth sideband lobe which is centered near 74.6 kHz. =
The=20
spectral gaps are on </FONT></DIV><FONT size=3D2 face=3DArial>
<DIV><FONT size=3D2 face=3DArial> 74916.666 Hz, </FONT></DIV>
<DIV><FONT size=3D2 face=3DArial> 74270.833 Hz, </FONT></DIV>
<DIV><FONT size=3D2 face=3DArial> 73625.000 Hz, =
</FONT></DIV></FONT>
<DIV><FONT size=3D2 face=3DArial>with small and sharp central lines, =
presumably=20
caused by slight inbalances or nonlinearities in the=20
transmitter.</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT> </DIV>
<DIV><FONT size=3D2 face=3DArial>By these criteria, if you have the =
choice I=20
would recommend to operate somewhere near these gaps, but not =
exactly in=20
their middle, and also preferably not exactly on integer Hz=20
frequencies ;-)</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT> </DIV>
<DIV><FONT size=3D2 face=3DArial>Best 73,</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial>Markus (DF6NM)</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial><BR></FONT><FONT=20
face=3DArial><B>...</B></FONT></DIV></BODY></HTML>
------=_NextPart_000_002C_01CEF21E.2DCB4540--