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Date: Sat, 26 Feb 2011 15:17:21 +0100
From: =?UTF-8?B?U3RlZmFuIFNjaMOkZmVy?= <schaefer@iup.uni-heidelberg.de>
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References: <4D68D907.1000005@iup.uni-heidelberg.de> <1298717758.4379.2.camel@gerhard-desktop> <483B525F6C7E42D1B5D226AB3E96611D@White>
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Subject: Re: VLF: OE5ODL,OE3GHB and DF6NM on 8970 Hz
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Markus, VLF,


Am 26.02.2011 14:27, schrieb Markus Vester:
> DHO 23.4 kHz is received simultaneously by a small ferrite antenna to=20
> lock the TX samplerate.

Maybe this should be pointed out a little more detailed.
While it was a quasi common thinking in the last months, that it is=20
impossible to receive a VLF MSK transmitter (like DHO38 or GQD) _during=20
transmitting_  below 9 kHz (due to the very high field strengths near=20
the TX coil and wire), your and Gerhard's experiments show that it is=20
possible indeed, if a resonated ferrite antenna is used. I've built the=20
same and can receive DHO38 at 20 dB SNR in 3 Hz. The attenuation of a 9=20
kHz signal against 23.4 kHz is about 40 dB. The dynamic range of the=20
soundcard allows another 80 dB before overload occurs. Additionally=20
there is a very narrow directivity of this antenna (-10 dB at +-30 deg).

The few VLF transmitting stations may use this method as an alternative=20
to a GPS locked VFO, if SpecLab is used to generate the TX frequency. I=20
will use this antenna as a redundant system to lock my VFO in the next=20
experiment. Maybe there are some advantages regarding EMC.
RX stations may use this method too since the strongest MSK transmitter=20
can be choosen, even if the RX loop antenna points into another=20
direction! (Stereo mode necessary)

A photo of my simple ferrite RX antenna for DHO38 is here:=20
http://dl.dropbox.com/u/19882028/DHO38%20ferrite%20RX%20antenna.JPG
34.3 nF is used to resonate to 23.4 kHz. The output winding has about 25=
=20
turns while the primary has about 200 turns.

73, Stefan/DK7FC


> Markus (DF6NM)
>
> *From:* Gerhard Hickl <mailto:gerhard.hickl@aon.at>
> *Sent:* Saturday, February 26, 2011 11:55 AM
> *To:* rsgb_lf_group@blacksheep.org <mailto:rsgb_lf_group@blacksheep.org>
> *Subject:* Re: VLF: OE5ODL and OE3GHB active on 8970 Hz
>
> Hi Stefan and group!
>
> In the moment I'm running on GPS-Sync and will switch to DHO38-Lock in=
=20
> a few minutes. I'm curious about the stability.
>
> Antenna-current is as usual about 550-580mA.
>
> Beside my plan to run a QRSS10 X-Band QSO with OK2BVG soon, no further=
=20
> plans right now.
>
> 73
>
> OE3GHB
> Gerhard
>
>
>
> Am Samstag, den 26.02.2011, 11:42 +0100 schrieb Stefan Sch=C3=A4fer:
> LF,
>
> The season is slowly passing, the average QRN is significantly=20
> rising. But today the QRN is low and both Austrian VLF TX stations=20
> are transmitting. OE3GHB is about 15 dB above noise in 424 uHz on=20
> 8969.98 Hz.
>
> Some new projects on your side? There's not much activity these days...
>
> 73, Stefan/DK7FC
>
>
>

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</head>
<body bgcolor=3D"#ffffff" text=3D"#000000">
Markus, VLF,<br>
<br>
<br>
Am 26.02.2011 14:27, schrieb Markus Vester:
<blockquote cite=3D"mid:483B525F6C7E42D1B5D226AB3E96611D@White"   type=3D"=
cite">
  <div>DHO 23.4 kHz is received simultaneously by a small ferrite
antenna to lock the TX samplerate.</div>
</blockquote>
<br>
Maybe this should be pointed out a little more detailed.<br>
While it was a quasi common thinking in the last months, that it is
impossible to receive a VLF MSK transmitter (like DHO38 or GQD) <u>during
transmitting</u>=C2=A0 below 9 kHz (due to the very high field strengths
near the TX coil and wire), your and Gerhard's experiments show that it
is possible indeed, if a resonated ferrite antenna is used. I've built
the same and can receive DHO38 at 20 dB SNR in 3 Hz. The attenuation of
a 9 kHz signal against 23.4 kHz is about 40 dB. The dynamic range of
the soundcard allows another 80 dB before overload occurs. Additionally
there is a very narrow directivity of this antenna (-10 dB at +-30
deg). <br>
<br>
The few VLF transmitting stations may use this method as an alternative
to a GPS locked VFO, if SpecLab is used to generate the TX frequency. I
will use this antenna as a redundant system to lock my VFO in the next
experiment. Maybe there are some advantages regarding EMC.<br>
RX stations may use this method too since the strongest MSK transmitter
can be choosen, even if the RX loop antenna points into another
direction! (Stereo mode necessary)<br>
<br>
A photo of my simple ferrite RX antenna for DHO38 is here:
<a class=3D"moz-txt-link-freetext" href=3D"http://dl.dropbox.com/u/1988202=
8/DHO38%20ferrite%20RX%20antenna.JPG">http://dl.dropbox.com/u/19882028/DHO=
38%20ferrite%20RX%20antenna.JPG</a><br>
34.3 nF is used to resonate to 23.4 kHz. The output winding has about
25 turns while the primary has about 200 turns.<br>
<br>
73, Stefan/DK7FC<br>
<br>
<br>
<blockquote cite=3D"mid:483B525F6C7E42D1B5D226AB3E96611D@White"   type=3D"=
cite">
  <div><font face=3D"Arial" size=3D"2">Markus (DF6NM)</font></div>
  <div>=C2=A0</div>
  <div   style=3D"font-family: Tahoma; font-style: normal; font-variant:=
 normal; font-weight: normal; font-size: 10pt; line-height: normal; font-s=
ize-adjust: none; font-stretch: normal; -x-system-font: none;">
  <div><br>
  </div>
  <div   style=3D"background: rgb(245, 245, 245) none repeat scroll 0% 0%;=
 -moz-background-clip: border; -moz-background-origin: padding; -moz-backg=
round-inline-policy: continuous;">
  <div style=3D""><b>From:</b> <a moz-do-not-send=3D"true"   title=3D"mail=
to:gerhard.hickl@aon.at  STRG + Klicken, um Verkn=C3=BCpfung zu folgen" =
  href=3D"mailto:gerhard.hickl@aon.at">Gerhard Hickl</a> </div>
  <div><b>Sent:</b> Saturday, February 26, 2011 11:55 AM</div>
  <div><b>To:</b> <a moz-do-not-send=3D"true"   title=3D"mailto:rsgb_lf_gr=
oup@blacksheep.org  STRG + Klicken, um Verkn=C3=BCpfung zu folgen"   href=
=3D"mailto:rsgb_lf_group@blacksheep.org">rsgb_lf_group@blacksheep.org</a>
  </div>
  <div><b>Subject:</b> Re: VLF: OE5ODL and OE3GHB active on 8970 Hz</div>
  </div>
  </div>
  <div><br>
  </div>
Hi Stefan and group!<br>
  <br>
In the moment I'm running on GPS-Sync and will switch to DHO38-Lock in
a few minutes. I'm curious about the stability.<br>
  <br>
Antenna-current is as usual about 550-580mA.<br>
  <br>
Beside my plan to run a QRSS10 X-Band QSO with OK2BVG soon, no further
plans right now.<br>
  <br>
73<br>
  <br>
OE3GHB<br>
Gerhard<br>
  <br>
  <br>
  <br>
Am Samstag, den 26.02.2011, 11:42 +0100 schrieb Stefan Sch=C3=A4fer:<br>
LF,<br>
  <br>
The season is slowly passing, the average QRN is significantly
rising.=C2=A0But today the QRN is low and both Austrian VLF TX stations
are=C2=A0transmitting. OE3GHB is about 15 dB above noise in 424 uHz on
8969.98 Hz.<br>
  <br>
Some new projects on your side? There's not much activity these days...<br=
>
  <br>
73, Stefan/DK7FC<br>
  <br>
  <br>
  <br>
</blockquote>
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