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Date: Wed, 26 May 2010 22:28:59 +0100
Message-ID: <AANLkTim-VaDofVEng_rAEK1Bq3klCXrkD6AtUiPtT2t-@mail.gmail.com>
From: Roger Lapthorn <rogerlapthorn@gmail.com>
To: rsgb_lf_group@blacksheep.org
DomainKey-Status: good (testing) 
Subject: Re: LF: AW: 8.97kHz - Near field and radiated signals?
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Stefan, Rik (*et al* dreamers),

All noted regarding QRSS modes and likely impact on the near field range
expected sub-9kHz - thanks all. Yes, I shall have to try it and see what
happens in reality.

Update on the near-field test work today:

   - Tried several things to improve the earth-mode transmitter, but none
   resulted in an improvement. The matching to the electrodes is optimised=
 and
   I am putting about 4-5W into the ground with a measured current of arou=
nd
   0.3A. I've yet to try elevating the feed wire to the far electrode to
   increase the effective loop area. This will also give some indication=
 of the
   size of the effective loop area within the ground and confirm the main
   transmission mode is induction. This will have to wait until later in=
 June
   now as I cannot do tests next week (grandson here and using the shack=
 as a
   bedroom). Also worth trying later will be replacing the 2 electrodes wi=
th a
   single continuous loop at the TX end to compare signal levels (loop are=
a
   will be smaller but current higher).
   - Tried a different "loop-amp-HPF-amp" RX arrangement but range was the
   same at 0.42kms before no further copy by ear.
   - Tried my "back-to-front SBL1" up-converter (that works fine with SAQ)
   TXing at 5kHz with the loop and a small preamp, but sensitivity was poo=
r. I
   need to work out why.

Tomorrow, if time permits, I may try to do a full 360 degree coverage map
with the current best TX/RX set-up i.e. doing a more thorough walk-about
test in all directions around the QTH rather than just in the fields to th=
e
south. Also, I may try taking the PC too and doing a screen grab of the
signal at the limit of audible reception (or further) in the best directio=
n.

After tomorrow I shall be on 2.5yr old grandson duty for a week taking him
to drive toy tractors, going to the park, painting, cooking and playing ca=
rs
:-)  Grampy will have to resume playing with *his* toys after he goes home=
.

73s
Roger G3XBM



2010/5/26 Stefan Sch=E4fer <schaefer@hst.tu-darmstadt.de>

> Hi Roger, Rik, VLF,
>
> That's what i meant, try it in QRSS/DFCW 600 (or 400). Doing it practica=
lly
> is more fun and gives a secure answer if it works or not. Better for hea=
lth
> than reading papers in front of the PC. All in all, the best you can do=
 ;-)
> I wish i would have the next receiving station in 3 km! Maybe i should
> visit the Heidelbergs radio club, maybe there are some interested OMs th=
at
> can be motivated. In the Darmstadts club i do not really have any hope=
 ;-)
>
> 73 es gl!
>
> Horst: Any news about your ground electrodes?
>
> Stefan/DK7FC
>
> ________________________________
>
> Von: owner-rsgb_lf_group@blacksheep.org im Auftrag von Roger Lapthorn
> Gesendet: Mi 26.05.2010 12:51
> An: rsgb_lf_group@blacksheep.org
> Betreff: Re: LF: AW: 8.97kHz - Near field and radiated signals?
>
>
> Thanks to all for the explanations.
> I'm glad others get confused too!!
>
> 73s
> Roger G3XBM
>
>
>


--=20
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/user/g3xbm
G3XBM    GQRP 1678      ISWL G11088

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Content-Transfer-Encoding: quoted-printable

Stefan, Rik (<i>et al</i> dreamers),<br><br>All noted regarding QRSS modes=
 and likely impact on the near field range expected sub-9kHz - thanks all.=
 Yes, I shall have to try it and see what happens in reality.<br><br>Updat=
e on the near-field test work today:<br>
<ul><li>Tried several things to improve the earth-mode transmitter, but no=
ne resulted in an improvement. The matching to the electrodes is optimised=
 and I am putting about 4-5W into the ground with a measured current of ar=
ound 0.3A. I&#39;ve yet to try elevating the feed wire to the far electrod=
e to increase the effective loop area. This will also give some indication=
 of the size of the effective loop area within the ground and confirm the=
 main transmission mode is induction. This will have to wait until later=
 in June now as I cannot do tests next week (grandson here and using the=
 shack as a bedroom). Also worth trying later will be replacing the 2 elec=
trodes with a single continuous loop at the TX end to compare signal level=
s (loop area will be smaller but current higher).<br>
</li><li>Tried a different &quot;loop-amp-HPF-amp&quot; RX arrangement but=
 range was the same at 0.42kms before no further copy by ear.</li><li>Trie=
d my &quot;back-to-front SBL1&quot; up-converter (that works fine with SAQ=
) TXing at 5kHz with the loop and a small preamp, but sensitivity was poor=
. I need to work out why.<br>
</li></ul><div class=3D"gmail_quote">Tomorrow, if time permits, I may try=
 to do a full 360 degree coverage map with the current best TX/RX set-up=
 i.e. doing a more thorough walk-about test in all directions around the=
 QTH rather than just in the fields to the south. Also, I may try taking=
 the PC too and doing a screen grab of the signal at the limit of audible=
 reception (or further) in the best direction.<br>
<br>After tomorrow I shall be on 2.5yr old grandson duty for a week taking=
 him to drive toy tractors, going to the park, painting, cooking and playi=
ng cars :-)=A0 Grampy will have to resume playing with <i>his</i> toys aft=
er he goes home.<br>
<br>73s<br>Roger G3XBM<br><br><br><br>2010/5/26 Stefan Sch=E4fer <span dir=
=3D"ltr">&lt;<a href=3D"mailto:schaefer@hst.tu-darmstadt.de">schaefer@hst.=
tu-darmstadt.de</a>&gt;</span><br><blockquote class=3D"gmail_quote" style=
=3D"margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204);=
 padding-left: 1ex;">
Hi Roger, Rik, VLF,<br>
<br>
That&#39;s what i meant, try it in QRSS/DFCW 600 (or 400). Doing it practi=
cally is more fun and gives a secure answer if it works or not. Better for=
 health than reading papers in front of the PC. All in all, the best you=
 can do ;-)<br>

I wish i would have the next receiving station in 3 km! Maybe i should vis=
it the Heidelbergs radio club, maybe there are some interested OMs that ca=
n be motivated. In the Darmstadts club i do not really have any hope ;-)<b=
r>

<br>
73 es gl!<br>
<br>
Horst: Any news about your ground electrodes?<br>
<br>
Stefan/DK7FC<br>
<div class=3D"im"><br>
________________________________<br>
<br>
Von: <a href=3D"mailto:owner-rsgb_lf_group@blacksheep.org">owner-rsgb_lf_g=
roup@blacksheep.org</a> im Auftrag von Roger Lapthorn<br>
</div>Gesendet: Mi 26.05.2010 12:51<br>
An: <a href=3D"mailto:rsgb_lf_group@blacksheep.org">rsgb_lf_group@blackshe=
ep.org</a><br>
Betreff: Re: LF: AW: 8.97kHz - Near field and radiated signals?<br>
<div><div></div><div class=3D"h5"><br>
<br>
Thanks to all for the explanations.<br>
I&#39;m glad others get confused too!!<br>
<br>
73s<br>
Roger G3XBM<br>
<br>
<br>
</div></div></blockquote></div><br><br clear=3D"all"><br>-- <br><a href=3D=
"http://g3xbm-qrp.blogspot.com/">http://g3xbm-qrp.blogspot.com/</a><br><a=
 href=3D"http://www.g3xbm.co.uk">http://www.g3xbm.co.uk</a><br><a href=3D"=
http://www.youtube.com/user/g3xbm">http://www.youtube.com/user/g3xbm</a><b=
r>
G3XBM =A0 =A0GQRP 1678 =A0 =A0 =A0ISWL G11088<br>

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