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Date: Mon, 21 Jun 2010 17:55:55 +0100
Message-ID: <AANLkTimywgRud4c6cI114258m-WA6CoyA1tWaTIm0LBu@mail.gmail.com>
From: Roger Lapthorn <rogerlapthorn@gmail.com>
To: rsgb_lf_group@blacksheep.org
Cc: M0BXT <andrew@tetrode.co.uk>
DomainKey-Status: good (testing) 
Subject: LF: Earth mode DXing today - 3.6kms!
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*MODS TO THE SYSTEM*

Some *significant* steps taken with my local earth mode / induction tests
today, which I'll summarise here. Spectran screen captures will appear on my
earth mode web page
<http://sites.google.com/site/g3xbmqrp/Home/earthmode>tomorrow.

   - Firstly, having installed the K1EL keyer chip, I decided to use its
   internal 800Hz sidetone oscillator, after a bit of LP filtering, to drive my
   4W PA. This arrangement now allows me to run either QRSS3 or 10wpm CW
   beacons on 800Hz at the flick of a switch. It is more stable than the
   external twin-tee oscillator I was using and is perfectly suitable for QRSS3
   at audio frequencies.
   - Secondly, I modified my loop/preamp to have marginally better
   sensitivity at around 700-900Hz.
   - A quick "by ear" test with the switch in the 10wpm position and the
   0.5km range I'd managed before was achieved using the 80cm loop and the 20m
   baseline earth electrodes.

*QRSS3 DX*

Now here comes the *real* fun. At this point I decided to take my loop,
preamp and laptop equipped with Spectran out into the field to see what I
could see/hear.

   - My first location was a field* 0.75km* south of the QTH just out of the
   village. Although nothing could be heard, the QRSS trace was solid on the
   screen.
   - Next step was to proceed further south along the Heath Road out of
   Burwell (QTH JO02dg) to a point* 2.5km* away from the QTH. Again, with
   Spectran, a good signal was visible on the screen. At one point when
   rotating the loop I could hear the signal too.
   - The next test was to go out of the village on a different road (towards
   Cambridge) to a car park adjacent to the Devils Dyke. This was
*1.4km*away from the TX but about 40 degrees further to the west than
the earlier
   test locations. Immediately the loop was set up (leaning against the back of
   the car) a good clear signal was visible, again no audible signal though.
   - At this point I decided to "go for broke" and drove down another rural
   lane to a roadside spot *3.6km* away from home, but in the direction of
   fire of the TX earth electrode loop. Setting up beside the country lane I
   could see the QRSS signal on the screen!! Best orientation was with the loop
   orthogonal to the village, which by now was too far away to see over the
   slightly rising ground.

At this point my laptop batteries were dying and I had to get some food for
my wife for tea, so I packed up and came home, very happy.
*
CONCLUSIONS*

   - Going from 10wpm CW to QRSS3 has made an amazing difference: signals
   that cannot be heard are visible, and at decent distances. This is a new
   experience for me, but not others here.
   - The free running sidetone oscillator in the K1EL keyer is fine for
   QRSS3, certainly for tests of about 1-2 hours long.
   - I suspect some "utility coupling" is going on, although at the
   furtherest point loop orientation did line up with the village. Is the
   signal propagating along the water pipes to some extent?
   - With "utility coupling" I suspect that getting a report from G6ALB in
   the next village will already be possible on VLF as I've already heard my
   signal at a greater distance than he is from me.
   - At VLF, I am wondering just how far is possible in semi-rural areas
   with manageable 50Hz noise levels (it is well filtered in my RX) and with
   some degree of "utility coupling" which is inevitable in today's world where
   pipes and wires criss-cross everywhere.
   - Even with just 4W and QRSS, remarkable distances can be achieved.
   Clearly I could get further than 3.6km already with the same equipment at
   each end.

*NEXT STEPS
*

   - I need a location right out in the wilds (a bit hard to find in SE
   England) for further tests, to see what performance is like without any
   coupling into water pipes etc.*.
   *
   - Add the screen shots and audio clips to the sub-9kHz
webpage<http://sites.google.com/site/g3xbmqrp/Home/earthmode>
   .
   - Increase the area of the TX loop part that is in the air as this could
   add another 3dB to signal* *level.
   - More power? Loops at both ends? ....?*
   *

73s
Roger G3XBM
-- 
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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<b>MODS TO THE SYSTEM</b><br><br>Some <u>significant</u> steps taken with=
 my local earth mode / induction tests today, which I&#39;ll summarise her=
e. Spectran screen captures will appear on my <a href=3D"http://sites.goog=
le.com/site/g3xbmqrp/Home/earthmode">earth mode web page</a> tomorrow. <br=
>

<ul><li>Firstly, having installed the K1EL keyer chip, I decided to use it=
s internal 800Hz sidetone oscillator, after a bit of LP filtering, to driv=
e my 4W PA. This arrangement now allows me to run either QRSS3 or 10wpm CW=
 beacons on 800Hz at the flick of a switch. It is more stable than the ext=
ernal twin-tee oscillator I was using and is perfectly suitable for QRSS3=
 at audio frequencies.<br>

</li><li>Secondly, I modified my loop/preamp to have marginally better sen=
sitivity at around 700-900Hz.</li><li>A quick &quot;by ear&quot; test with=
 the switch in the 10wpm position and the 0.5km range I&#39;d managed befo=
re was achieved using the 80cm loop and the 20m baseline earth electrodes.=
<br>

</li></ul><b>QRSS3 DX</b><br><br>Now here comes the <u>real</u> fun. At th=
is point I decided to take my loop, preamp and laptop equipped with Spectr=
an out=20
into the field to see what I could see/hear.<ul><li>My first location was=
 a field<b> 0.75km</b> south of the QTH just out of the village. Although=
 nothing could be heard, the QRSS trace was solid on the screen.</li><li>N=
ext step was to proceed further south along the Heath Road out of Burwell=
 (QTH JO02dg) to a point<b> 2.5km</b> away from the QTH. Again, with Spect=
ran, a good signal was visible on the screen. At one point when rotating=
 the loop I could hear the signal too.<br>

</li><li>The next test was to go out of the village on a different road (t=
owards Cambridge) to a car park adjacent to the Devils Dyke. This was <b>1=
.4km</b> away from the TX but about 40 degrees further to the west than th=
e earlier test locations. Immediately the loop was set up (leaning against=
 the back of the car) a good clear signal was visible, again no audible si=
gnal though.</li>

<li>At this point I decided to &quot;go for broke&quot; and drove down ano=
ther rural lane to a roadside spot <b>3.6km</b> away from home, but in the=
 direction of fire of the TX earth electrode loop. Setting up beside the=
 country lane I could see the QRSS signal on the screen!! Best orientation=
 was with the loop orthogonal to the village, which by now was too far awa=
y to see over the slightly rising ground.</li>

</ul>At this point my laptop batteries were dying and I had to get some fo=
od for my wife for tea, so I packed up and came home, very happy.<br><b><b=
r>CONCLUSIONS</b><br><ul><li>Going from 10wpm CW to QRSS3 has made an amaz=
ing difference: signals that cannot be heard are visible, and at decent di=
stances. This is a new experience for me, but not others here.<br>
</li>
<li>The free running sidetone oscillator in the K1EL keyer is fine for QRS=
S3, certainly for tests of about 1-2 hours long.<br></li><li>I suspect som=
e &quot;utility coupling&quot; is going on, although at the furtherest poi=
nt loop orientation did line up with the village. Is the signal propagatin=
g along the water pipes to some extent?<br>

</li><li>With &quot;utility coupling&quot; I suspect that getting a report=
 from G6ALB in the next village will already be possible on VLF as I&#39;v=
e already heard my signal at a greater distance than he is from me.</li>
<li>At VLF, I am wondering just how far is possible in semi-rural areas wi=
th manageable 50Hz noise levels (it is well filtered in my RX) and with so=
me degree of &quot;utility coupling&quot; which is inevitable in today&#39=
;s world where pipes and wires criss-cross everywhere.</li>

<li>Even with just 4W and QRSS, remarkable distances can be achieved. Clea=
rly I could get further than 3.6km already with the same equipment at each=
 end.<br></li></ul><b>NEXT STEPS<br></b><ul><li>I need a location right ou=
t in the wilds (a bit hard to find in SE England) for further tests, to se=
e what performance is like without any coupling into water pipes etc.<b>.=
 <br>

</b></li><li>Add the screen shots and audio clips to the <a href=3D"http:/=
/sites.google.com/site/g3xbmqrp/Home/earthmode">sub-9kHz webpage</a>.</li>=
<li>Increase the area of the TX loop part that is in the air as this could=
 add another 3dB to signal<b> </b>level.</li>
<li>More power? Loops at both ends? ....?<b><br></b></li></ul>73s<br>Roger=
 G3XBM<br>-- <br><a href=3D"http://g3xbm-qrp.blogspot.com/" target=3D"_bla=
nk">http://g3xbm-qrp.blogspot.com/</a><br>
<a href=3D"http://www.g3xbm.co.uk" target=3D"_blank">http://www.g3xbm.co.u=
k</a><br><a href=3D"http://www.youtube.com/user/g3xbm" target=3D"_blank">h=
ttp://www.youtube.com/user/g3xbm</a><br>G3XBM =A0 =A0GQRP 1678 =A0 =A0 =A0=
ISWL G11088<br>

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