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References: <33d07ccc43ec486d83d0d460928f26ad@kabelmail.de>
Date: Tue, 8 Mar 2011 19:51:32 +0000
Message-ID: <AANLkTimhxKt3FxUtStDVeu3LnumSdQ7CtbqzOouVDOdT@mail.gmail.com>
From: Roger Lapthorn <rogerlapthorn@gmail.com>
To: rsgb_lf_group@blacksheep.org
DomainKey-Status: good (testing) 
Subject: Re: LF: VLF dj8wx on 8970.022Hz
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Uwe

Nothing visible on my grabber
https://dl.dropbox.com/u/15047843/xbm_grab.jpgyet this evening but I
have a high noise level in the evening hours from
lights, TVs etc.Leave the TX running overnight please as I hope to see your
signal after midnight and through tomorrow morning. In the 423uHz bandwidth
and with the slow scroll speed it will be more difficult to see than when
you were sending a continuous carrier a few days ago.

BTW, you may want to try the simple ERP estimate I made on G3XIZ's signal
using an assumption for the effective height of the Marconi to derive a
radiation resistance figure and using the measured antenna current. Chris
tells me that my estimate was within 3dB of the figure calculated using the
fempto-Tesla measurements by Paul Nicholson. It won't be accurate but may
give you an "order of magnitude" estimate (uWs or mWs). As you were copied
by several UK stations at around 600-700km a few days ago you must be at
least 20-30dB (?) higher ERP that G3XIZ whose ERP has now been estimated as
between1-2uW by 2 different methods. I would be surprised if your ERP was
not at least 500uW.

73s
Roger G3XBM



On 8 March 2011 18:27, <uwe-jannsen@kabelmail.de> wrote:

> Hi all,
>
>
>
> Im doing some measurements trying to find out how low (high?) the ERP of my
> system is.
>
>
>
> the test lead of the oscilloscope in use has a resistor of 10Mohm. The
> oscilloscope advise text says that I have to multiply the result by 10.
>
> OK. I added two other 10Mohm  in series multiplyed the result by 1000 and
> got 40000Vpp
>
> using the twentieth of max TX power. 40kV? Is that possible?
>
> the current from the coile foot into the radials was 0.145A (3 A with max
> power).
>
> I cant measure the Tesla voltage when the  power is raised because the
> oscilloscope or other
>
> instruments indicate results without connected to the object under test.
>
>
>
> the station is on the air in mode QRSS3600 on 8970.022Hz since today
> 1640UTC.
>
>
>
> current into the radials: one Ampere.
>
>
>
> who will try to calculate the ERP?
>
> the aerial in use can be seen at
>
>
>
> http://dj8wx-dl.de/hompage500kHz/TX%20equipment.htm
>
>
>
> fourth pic on the site. The shown 23m long wire has been lengthened to 43m.
>
>
>
> best regards
>
> Uwe/dj8wx
>
>
>
>


-- 
g3xbm-qrp.blogspot.com/
www.g3xbm.co.uk
www.youtube.com/user/g3xbm
<http://vlf_grabber>G3XBM   GQRP 1678    ISWL G11088

--90e6ba6e857c6454d7049dfdf004
Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable

Uwe<br><br>Nothing visible on my grabber <a href=3D"https://dl.dropbox.com=
/u/15047843/xbm_grab.jpg">https://dl.dropbox.com/u/15047843/xbm_grab.jpg</=
a> yet this evening but I have a high noise level in the evening hours fro=
m lights, TVs etc.Leave the TX running overnight please as I hope to see=
 your signal after midnight and through tomorrow morning. In the 423uHz ba=
ndwidth and with the slow scroll speed it will be more difficult to see th=
an when you were sending a continuous carrier a few days ago.<br>
<br>BTW, you may want to try the simple ERP estimate I made on G3XIZ&#39;s=
 signal using an assumption for the effective height of the Marconi to der=
ive a radiation resistance figure and using the measured antenna current.=
 Chris tells me that my estimate was within 3dB of the figure calculated=
 using the fempto-Tesla measurements by Paul Nicholson. It won&#39;t be ac=
curate but may give you an &quot;order of magnitude&quot; estimate (uWs or=
 mWs). As you were copied by several UK stations at around 600-700km a few=
 days ago you must be at least 20-30dB (?) higher ERP that G3XIZ whose ERP=
 has now been estimated as between1-2uW by 2 different methods. I would be=
 surprised if your ERP was not at least 500uW.<br>
<br>73s<br>Roger G3XBM<br><br><br><br><div class=3D"gmail_quote">On 8 Marc=
h 2011 18:27,  <span dir=3D"ltr">&lt;<a href=3D"mailto:uwe-jannsen@kabelma=
il.de">uwe-jannsen@kabelmail.de</a>&gt;</span> wrote:<br><blockquote class=
=3D"gmail_quote" style=3D"margin: 0pt 0pt 0pt 0.8ex; border-left: 1px soli=
d rgb(204, 204, 204); padding-left: 1ex;">
<span style=3D"font-family: Arial; font-size: 13px;"><p>Hi all,</p>
<p>=A0</p>
<p><span>Im doing some measurements trying to find out how low (high?) the=
 ERP of my system is.</span></p>
<p><span>=A0</span></p>
<p><span>the test lead of the oscilloscope in use has a resistor of 10Mohm=
. The oscilloscope advise text says that I have to multiply the result by=
 10.</span></p>
<p><span>OK. I added two other 10Mohm=A0 in series multiplyed the result=
 by 1000 and got 40000Vpp</span></p>
<p><span>using the twentieth of max TX power. 40kV? Is that possible?</spa=
n></p>
<p><span>the current from the coile foot into the radials was 0.145A (3 A=
 with max power). </span></p>
<p><span>I cant measure the Tesla voltage when the =A0power is raised beca=
use the oscilloscope or other </span></p>
<p><span>instruments indicate results without connected to the object unde=
r test.</span></p>
<p><span>=A0</span></p>
<p><span>the station is on the air in mode QRSS3600 on 8970.022Hz since to=
day 1640UTC.</span></p>
<p><span>=A0</span></p>
<p><span>current into the radials: one Ampere.</span></p>
<p><span>=A0</span></p>
<p><span>who will try to calculate the ERP?</span></p>
<p><span>the aerial in use can be seen at </span></p>
<p><span>=A0</span></p>
<p><span><a href=3D"http://dj8wx-dl.de/hompage500kHz/TX%20equipment.htm"=
 target=3D"_blank">http://dj8wx-dl.de/hompage500kHz/TX%20equipment.htm</a>=
</span></p>
<p><span>=A0</span></p>
<p><span>fourth pic on the site. The shown 23m long wire has been lengthen=
ed to 43m.</span></p>
<p><span>=A0</span></p>
<p><span>best regards</span></p>
<p><span>Uwe/dj8wx </span></p>
<p><span>=A0</span></p>
<br></span></blockquote></div><br><br clear=3D"all"><br>-- <br><a href=3D"=
http://g3xbm-qrp.blogspot.com/" target=3D"_blank">g3xbm-qrp.blogspot.com/<=
/a><br><a href=3D"http://www.g3xbm.co.uk" target=3D"_blank">www.g3xbm.co.u=
k</a><br>
<a href=3D"http://www.youtube.com/user/g3xbm" target=3D"_blank">www.youtub=
e.com/user/g3xbm</a><br><a href=3D"http://vlf_grabber" target=3D"_blank"><=
/a>G3XBM=A0=A0 GQRP 1678=A0=A0=A0 ISWL G11088<br>

--90e6ba6e857c6454d7049dfdf004--