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<P style="MARGIN-TOP: 0px" align=center><FONT
face="Times,Times New Roman,serif" size=6><SPAN class=style106
style="FONT-SIZE: 24px">144 MHz Long Distance Radio
Propagation</SPAN></FONT></P>
<P style="MARGIN-TOP: 0px" align=center><FONT
face="Times,Times New Roman,serif" size=6><SPAN class=style106
style="FONT-SIZE: 24px">from Western Europe into the Atlantic
Ocean</SPAN></FONT></P>
<P style="MARGIN-TOP: 0px" align=center><FONT
face="Times,Times New Roman,serif" size=5><SPAN class=style109
style="FONT-SIZE: 18px">Analysis of tropospheric inversion layers and the
atmospheric refraction index</SPAN></FONT></P>
<P style="MARGIN-TOP: 0px" align=center><FONT
face="Times,Times New Roman,serif" size=5><SPAN class=style109
style="FONT-SIZE: 18px">along radiowave propagation paths exceeding 3700
kilometers</SPAN></FONT></P>
<P style="MARGIN-TOP: 0px" align=center><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px">Volker Grassmann,
DF5AI</SPAN></FONT></P>
<P style="MARGIN-TOP: 0px" align=center><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px">September 6, 2005 - updated December
12, 2005</SPAN></FONT></P></TD>
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<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><B><FONT
face=Arial size=4><SPAN class=style107
style="FONT-SIZE: 14px">Introduction</SPAN></FONT></B><FONT face=Arial
size=4><SPAN class=style108 style="FONT-SIZE: 14px"></SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">Tropospheric radio
links between England/Ireland and the Canary Islands have been reported
several times in recent years and G4ASR even considers 144 MHz contacts
between the British and the Canary Isles an every year experience (see,
e.g., [</SPAN></FONT><A
href="http://www.df5ai.net/ArticlesDL/VLDP_EA8.pdf"><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px">1</SPAN></FONT></A><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">] and the references
cited therein). In August 2005, however, VHF radio amateurs have reported
record-breaking results in tropospheric dxing which will be briefly
summarized in this document. To explain the meteorological origin of this
extraordinary dx QSOs, we will analyse upper air sounding data and will
calculate the vertical distribution of the atmospheric refractive index
along the radio propagation paths. Between the northwest of Spain and the
Canary Islands, intense inversion layers are found between 1000m and 2000m
altitude indicating significant discontinuities in air temperature and, in
particular, in air humidity. Thus, significant discontinuities are also
present in the vertical distribution of the atmospheric refractive index
which has apparently enabled ducting of radiowaves and, in consequence,
long distance 144 MHz communication links exceeding path lenghts of more
than 3700km.</SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><B><FONT
face=Arial size=4><SPAN class=style107 style="FONT-SIZE: 14px">144 MHz dx
band openings in June and July 2005</SPAN></FONT></B><FONT face=Arial
size=4><SPAN class=style108 style="FONT-SIZE: 14px"></SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">Considering the many
dx QSOs between Spain and Portugal on one hand and the Azores, Madeira and
the Canary Islands on the other hand, it is almost impossible to provide a
detailed picture of the dx scenarios in June, July and August 2005. It
appears that dx distances between, say 1000 and 2000 kilometers, and even
more, were an every day experience to many radio amateurs, see the "tropo
reports" in [6]. As an example, we will briefly summarize the dx results
from Joachim (CT1HZE) located in IM57NH at the south coast of Portugal.
Among his QSOs to the Azores (around 1380 km), Joachim has in particular
established contacts to Mauretania, i.e. he heard the 5T5SN radio beacon
(which is operational since May 2005) and he worked the beacon operator
5T5SN (June 5) representing the very first 144 MHz contact between
Portugal and Mauretania (2245 km). Between July 9 and 19, Joachim had
several contacts even to the Cap Verde Islands, i.e. to D44TD
corresponding to a distance of 2681 km, [6]. This band openings have
supported dx QSOs on VHF, UHF and SHF too. On 432 MHz, Joachim worked Fred
(CU8AO) on the Azores (June 21, 1953 km) and, again, 5T5SN (July 6) and
the latter one represents the Portuguese terrestrial tropo record on 70 cm
wavelength. The very first SHF contact between the main land of Portugal
and the Azores was established by Joachim and Fred on July 6 (1296 MHz,
1953 km) which represents another Portuguese tropo record,
[6].</SPAN></FONT></P></TD>
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<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><B><FONT
face=Arial size=4><SPAN class=style107 style="FONT-SIZE: 14px">Very long
dx QSOs in August 2005</SPAN></FONT></B><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px"></SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">Remarkably, 144 MHz
radio stations from England and Ireland came into play too. On July 2, Tim
(G4LOH), located in IO70JC in southwest England, worked a number of radio
stations on the Canary Islands corresponding to distances around 2600 km
[</SPAN></FONT><A href="http://www.g4loh.com/"><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px">2</SPAN></FONT></A><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">]. On July 16, he
also received signals from the Azores (2344 km), i.e. from the CU8DUB
beacon.</SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><U><FONT
face=Arial><SPAN class=style1
style="FONT-SIZE: 11px">Note:</SPAN></FONT></U><FONT face=Arial><SPAN
class=style2 style="FONT-SIZE: 11px"> The above mentioned radio
beacons, i.e. 5T5SN and CU8DUB, are part of
the </SPAN></FONT><I><FONT face=Arial><SPAN class=style3
style="FONT-SIZE: 11px">Dubus Beacon Project</SPAN></FONT></I><FONT
face=Arial><SPAN class=style2 style="FONT-SIZE: 11px"> initiated by
the </SPAN></FONT><A href="http://www.dubus.org/"><FONT
face=Arial><SPAN class=style2 style="FONT-SIZE: 11px">Dubus
magazine</SPAN></FONT></A><FONT face=Arial><SPAN class=style2
style="FONT-SIZE: 11px">. This remarkable project deploys 50 and 144 MHz
radio beacons around the Atlantic Ocean and has activated the CU8DUB
transmitter just a couple of days before it was received by G4LOH. The
Dubus team around Joachim (DL8HCZ/CT1HZE), Dithmar (DF7KF), Nicholas
(5T5SN), Fred (CU8AO), and many others, currently plans to implement
another VHF beacon in Tunesia and has already put the Bermuda beacon
(VP9DUB) into the air. The project also plans VHF radio beacons in the
South Atlantic region, e.g. on Ascension Island.</SPAN></FONT><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px"></SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">The big bang came in
the morning of August 7: Tim, again, worked several EA8 stations and
finally managed two QSOs with Alex, RW1ZC/mm, travelling on a vessel close
to the west African sea coast [</SPAN></FONT><A
href="http://www.g4loh.com/"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">2</SPAN></FONT></A><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px">]. The distance of 3493 km landmarked
a new 144 MHz dx record in the IARU Region 1 [4]. On August 15, Charles
(EI5FK) came into play also working RW1ZC/mm in four independent QSOs
[</SPAN></FONT><A href="http://www.qsl.net/ei5fk"><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px">3</SPAN></FONT></A><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">]. Alex's ship has
changed its position though and the brand new IARU Region 1 record has
been extended even further to 3751 km [5], see the red line in figure 1.
Two weeks later, i.e. on August 29, it was Tim again managing another QSO
with Alex corresponding to 3444 km [</SPAN></FONT><A
href="http://www.g4loh.com/"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">2</SPAN></FONT></A><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px">].</SPAN></FONT></P></TD>
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<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><B><FONT
face=Arial size=4><SPAN class=style107 style="FONT-SIZE: 14px">The
refractive index N</SPAN></FONT></B><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px"></SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">Radio amateurs are
aware of long distance VHF propagation caused by tropospheric inversion
layers and it appears plausible to keep an eye on inversion layers when
interpreting the above mentioned dx QSOs. In this paper, however, we will
not discuss neither the creation nor the various types of atmospheric
inversion layers (interested readers may refer to basic information on
this subject, e.g., in [</SPAN></FONT><A
href="http://en.wikipedia.org/wiki/Temperature_inversion"><FONT
face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">10</SPAN></FONT></A><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px">], and to a more detailed discussion,
e.g., in [</SPAN></FONT><A
href="http://yosemite.epa.gov/oaqps/EOGtrain.nsf/fabbfcfe2fc93dac85256afe00483cc4/1c9d492b7ccef4fe85256b6d0064b4ee/$FILE/Lesson%204.pdf"><FONT
face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">11</SPAN></FONT></A><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px">] and [23]).</SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">Tropospheric
inversion layers may cause reflection and also ducting of radiowaves
resulting in long and very long radio commincation paths [12]. All this
phenomena may be interpreted by analyzing the refractive index N which
controls the radiowaves' ray path in the atmosphere. Calculating the
refractive index N, we obtain a summation of two terms, i.e. N =
N</SPAN></FONT><FONT face=Arial><SPAN class=style2
style="FONT-SIZE: 11px">d</SPAN></FONT><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">+N</SPAN></FONT><FONT face=Arial><SPAN
class=style2 style="FONT-SIZE: 11px">w</SPAN></FONT><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px"> where N</SPAN></FONT><FONT
face=Arial><SPAN class=style2 style="FONT-SIZE: 11px">d</SPAN></FONT><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px"> and
N</SPAN></FONT><FONT face=Arial><SPAN class=style2
style="FONT-SIZE: 11px">w</SPAN></FONT><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">denote the so-called </SPAN></FONT><I><FONT
face=Arial><SPAN class=style9
style="FONT-SIZE: 12px">dry </SPAN></FONT></I><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px">and the </SPAN></FONT><I><FONT
face=Arial><SPAN class=style9 style="FONT-SIZE: 12px">wet
term</SPAN></FONT></I><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">, respectively. The dry term is mainly controlled
by air temperature and air pressure, the wet term considers the air
humidity in particular (see the below formulas). In practice, the dry term
contributes about eighty percent to the actual value of N, i.e. the wet
term only contributes around twenty percent [12]. However,
N</SPAN></FONT><FONT face=Arial><SPAN class=style2
style="FONT-SIZE: 11px">w</SPAN></FONT><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px"> is typically more important than
N</SPAN></FONT><FONT face=Arial><SPAN class=style2
style="FONT-SIZE: 11px">d </SPAN></FONT><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px">in tropospheric radio propagation
because the wet term is a much more variable than the dry term
[12].</SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">Thus, inversion
layers relevant in VHF radio propagation may be identified by
discontinuities in the vertical profile of the dry and wet component of
the refractive index. In the following, both quantities are initially
represented by the air temperture and by the </SPAN></FONT><I><FONT
face=Arial><SPAN class=style9
style="FONT-SIZE: 12px">dewpoint</SPAN></FONT></I><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px"> which are both available in
meteorological data. The dewpoint denotes the temperature where the air's
water vapour content begins to condensate corresponding to 100% relative
humidity, see, e.g., [13] and [14]. In the following, we will refer to the
dewpoint because it is a convenient quantity which is measured in Celsius,
i.e. the air temperature and the dewpoint may be displayed in the same
temperature profile. In the temperature diagrams, dry air is indicated by
a more or less large difference between air temperature and the dewpoint,
in wet air, on the other hand, the difference is rather small. We will
finally compare the vertical profiles of air temperature and dewpoint with
the calculated profiles of the atmospheric refractive
index.</SPAN></FONT></P></TD>
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<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><B><FONT
face=Arial size=4><SPAN class=style107 style="FONT-SIZE: 14px">Upper air
sounding data</SPAN></FONT></B><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px"></SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">VHF radio amateurs
often refer to weather maps to understand (or to predict) actual dx
conditions in tropospheric radio propagation. In the European sector, for
example, the University of Cologne distributes actual weather patterns
which are considered in particular useful for VHF radio amateurs, see
[</SPAN></FONT><A
href="http://www.meteo.uni-koeln.de/meteo.php?show=En_We_We"><FONT
face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">8</SPAN></FONT></A><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px">]. Weather maps can provide
infomation on the horizontal distribution of, for example, air temperature
and pressure (at ground level or, alternatively, in higher altitudes) but
cannot provide detailed information on the vertical structure of the
troposphere.</SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">In this paper, we
refer to the </SPAN></FONT><I><FONT face=Arial><SPAN class=style9
style="FONT-SIZE: 12px">upper air sounding</SPAN></FONT></I><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">data which is
distributed in the internet by the University of Wyoming, see
[</SPAN></FONT><A
href="http://weather.uwyo.edu/upperair/sounding.html"><FONT
face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">7</SPAN></FONT></A><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px">]. The data provides a large variety
of detailed information, for example, on air temperature, air pressure,
dewpoint and other parameters between ground and more than 30.000m
altitude. This information is available for a large number of places
around the world (airports) typically at 00 and 12 UT. By using the
internet portal, the user may select various graphical presentations or,
alternatively, may access ASCII tables summarizing all data in
easy-to-handle data columns. All this information is useful in radio
propagation studies and has been applied, for example, in the analysis of
the May 20, 2003 dx opening between central Europe and the Canary Islands,
see [</SPAN></FONT><A
href="http://www.df5ai.net/ArticlesDL/VLDP_EA8.pdf"><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px">1</SPAN></FONT></A><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">]. Readers
interested in the backgrounds of upper air sounding may refer to the
internet tutorial given by the University of Columbia, see
[</SPAN></FONT><A
href="http://www.eos.ubc.ca/courses/atsc201/A201Resources/SoundingTutorial1/SoundingTutorial1Readings.html"><FONT
face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">9</SPAN></FONT></A><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px">].</SPAN></FONT></P></TD>
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<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><B><FONT
face=Arial size=4><SPAN class=style107 style="FONT-SIZE: 14px">Vertical
profiles of air temperature and dewpoint</SPAN></FONT></B></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">Figure 2 displays
the dx QSO between G4LOH in southwest England and RW1ZC/mm close to the
west African sea coast on August 7, 2005. The diagrams display the
vertical profile of air temperature (red) and dewpoint (blue) along the
radio propagation paths, i.e. at Camborne (southwest England), La Coruna
(northwest Spain), Funchal (Madeira), Guimar (Canary Islands), Sal (Cap
Verde Islands) and Dakar (Senegal), respectively. The meteorological data
was taken from the University of Wyoming web site (see [</SPAN></FONT><A
href="http://weather.uwyo.edu/upperair/sounding.html"><FONT
face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">7</SPAN></FONT></A><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px">] and the blue infobox) and has been
post-processed by using a spread-sheet computer program. The left column
displays sounding data from midnight, 00 UT, the right column displays the
12 UT data, i.e. this column is most representative with respect to the dx
QSOs between 0927 and 1149 UT. The QSO data was taken from G4LOH's
personal web site [</SPAN></FONT><A href="http://www.g4loh.com/"><FONT
face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">2</SPAN></FONT></A><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px">] and the map display is adopted from
the BeamFinder analysis software [</SPAN></FONT><A
href="http://www.beamfinder.net/"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">15</SPAN></FONT></A><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px">]. By clicking on figure 2, the user
may download the large version of the graphics.</SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">Tracing the
propagation path from England to west Africa, a number of remarkable
features attract our interest. At G4LOH's location, we find around 80%
relative air humidity between ground and 1000m altitude (see the station
Cambore at 12 UT and note the small difference between the red and the
blue line). At 1200m, however, the dewpoint (blue line) drops sharply from
-0.4C to -11C accompanied by a slight increase of 1 or 2 degree in air
temperature (the numerical values are taken from the original data table
which is not shown here). Between 1815m to 1900m altitude, the dewpoint
returns to air temperature by increasing sharply from -16C to more than
+1C reaching +5C at 2100m. Thus, between 1200m and 2000m, we are facing a
layer of relatively dry air (16% air humidity), the ambient troposphere
shows more than 70% relative humidity though.</SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">Near Spain (see the
station La Coruna at 12 UT), we find dry air in all height intervals which
is indicated by the relatively wide horizontal spacing between the red and
blue line (refering to the data table, the relative humidity decreases
from 50% at ground level to 13% at 2000m altitude). Thus, the radiowaves
have travelled in dry atmosphere and no significant discontinuity becomes
visible in the profile. This is however not true when consideriing Madeira
and the Canary Islands, see the stations Funchal and Guimar at 12 UT.
Here, we find intense inversion layers around 1800m (Funchal) and 1000m
(Guimar), respectively, indicated by a significant increase in air
temperature and an even more significant decrease in dewpoint. Further
south, those inversion layers however disappear, see the station Dakar at
the southern end of the chain of observatories (the positive peak around
8000m may be ignored because it is interpreted an inaccuracy in the
sounding data).</SPAN></FONT></P></TD>
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<TD><IMG height=1 alt=""
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src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=3 border=0 NOSEND="1"><IMG height=68
alt="Figure 2. Dx scenario on August 7, 2005. The diagrams display air temperature (red) and dewpoint (blue) between ground and 10.000 meters altitude measured along the radio propagation path between England and west Africa. Click image to obtain the large version."
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<TD><A
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<TD><A
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src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=46 border=0 NOSEND="1"><IMG height=13
alt="Figure 3. Dx scenario on August 15, 2005."
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src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=46 border=0 NOSEND="1"><IMG height=13
alt="Figure 4. Dx scenario on August 29, 2005."
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<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">In figure 3 and 4,
the same type of analysis is shown for the dx scenario on August 15 and
August 29, respectively. Without discussing the details, we also notice
sharp inversion layers between 1000m and 2000m altitude which appear to
concentrate in the sea area from northwest Spain down to the Canary
Islands. At lower latitudes, the inversion intensity is much smaller (see
the station Sal) and disappers altogether in the Dakar data (which might
have something to do with the fact that inversion layers over sea terrain
cannot be observed by the continental observatory at Dakar). At higher
latitudes, i.e. in England and Ireland, wet ground air develops into dry
air at higher altitudes without showing distinct layer-type features
though.</SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><B><FONT
face=Arial size=4><SPAN class=style107 style="FONT-SIZE: 14px">Discussing
the refractive index N</SPAN></FONT></B><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px"></SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">We have found strong
indication that all this dx QSOs were enabled by atmospheric inversion
layers between 1000m and 2000m altitude. Interpreting this results in
terms of the vertical gradient in the refractive index, VHF radio
propagation was mainly influenced by variations in the wet component
N</SPAN></FONT><FONT face=Arial><SPAN class=style2
style="FONT-SIZE: 11px">w</SPAN></FONT><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px"> of the refractive index N, i.e. air
temperature inversion has played a role too but was less important here.
This is also documented by figure 5 which displays the dry and wet term
and also the total refractive index N by using the data from Funchal on
August 7, 12 UT. Note the variability of the total index N which is almost
exclusively controlled by the variability of N</SPAN></FONT><FONT
face=Arial><SPAN class=style2 style="FONT-SIZE: 11px">w</SPAN></FONT><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px"> althougfh its
magnitude is much smaller than the magnitude of the dry
term.</SPAN></FONT></P></TD>
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<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">The refractive index
N should be actually referred to as the</SPAN></FONT><I><FONT
face=Arial><SPAN class=style9 style="FONT-SIZE: 12px">modified refractive
index</SPAN></FONT></I><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px"> which is commonly used in literature because
it provides values which are more convenient in practical applications
than the orginal physical index n. By using</SPAN></FONT></P></TD>
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<TABLE cellSpacing=0 cellPadding=0 width=380 border=0>
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<TD><IMG height=302 alt=FunchalN07080512UT
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/funchaln07080512u.gif"
width=379 border=0 NOSEND="1"></TD>
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<TD></TD>
<TD height=7></TD></TR>
<TR vAlign=top>
<TD><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"><BR><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=3 border=0 NOSEND="1"><IMG height=38
alt="Figure 5. Vertical profile of the refractive index N at Funchal on August 7, 2005, 12 UT. Nd and Nw denote the dry and wet term, respectively, its sum denotes the total index N."
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/objekt1a1a1.gif"
width=372 border=0 NOSEND="1"></TD>
<TD height=40></TD></TR>
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<TD width=379><IMG height=1 alt=""
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<TD width=1 height=1><IMG height=1 alt=""
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<TR vAlign=top>
<TD><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=131 border=0 NOSEND="1"><IMG height=27 alt=NFormulas
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/nformulas.gif"
width=177 border=0 NOSEND="1"></TD>
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<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">the refractive index
of, say n = 1.0003 now reads N = 300 which, by the way, corresponds to
typical values at low altitudes below 1000m. The total refractive index N
may be calculated by using the formula (see, e.g.,
[12]):</SPAN></FONT></P></TD>
<TD></TD>
<TD height=56></TD></TR>
<TR vAlign=top>
<TD colSpan=2></TD>
<TD height=2></TD></TR>
<TR vAlign=top>
<TD><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=93 border=0 NOSEND="1"><IMG height=71 alt=NFormulas1
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/nformulas1.gif"
width=177 border=0 NOSEND="1"></TD>
<TD></TD>
<TD height=71></TD></TR>
<TR vAlign=top>
<TD colSpan=2></TD>
<TD height=2></TD></TR>
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<TD>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">where T denotes the
air temperature in Kelvin, p the air pressure in hPa, f the relative
humidity (percent value divided by 100). The saturated water vapour
pressure e</SPAN></FONT><FONT face=Arial><SPAN class=style2
style="FONT-SIZE: 11px">s</SPAN></FONT><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px"> (which is also measured in hPa) is
calculated by using MAGNUS' empirical formula (see, e.g., [12],
[14])</SPAN></FONT></P></TD>
<TD></TD>
<TD height=70></TD></TR>
<TR vAlign=top>
<TD colSpan=2></TD>
<TD height=2></TD></TR>
<TR vAlign=top>
<TD><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=100 border=0 NOSEND="1"><IMG height=41 alt=NFormulas1a
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/nformulas1a.gif"
width=177 border=0 NOSEND="1"></TD>
<TD></TD>
<TD height=41></TD></TR>
<TR vAlign=top>
<TD colSpan=2></TD>
<TD height=2></TD></TR>
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<TD rowSpan=2>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">where t denotes the
air temperature measured in Celsius. With this mathematical tools and with
the Wyoming sounding data, radio amateurs may calculate vertical profiles
of the refractive index N in tropospheric radio propagation similar to
figure 5.</SPAN></FONT></P></TD>
<TD></TD>
<TD height=26></TD></TR>
<TR vAlign=top>
<TD colSpan=2></TD>
<TD height=30></TD></TR>
<TR>
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width=356 border=0 NOSEND="1"></TD>
<TD width=17><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=17 border=0 NOSEND="1"></TD>
<TD width=380><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=380 border=0 NOSEND="1"></TD>
<TD width=1 height=1><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD></TR></TBODY></TABLE>
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cellPadding=0 width=754 border=0>
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<TD></TD>
<TD height=1></TD></TR>
<TR vAlign=top>
<TD></TD>
<TD height=6></TD></TR>
<TR>
<TD width=752><IMG height=1 alt=""
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<TABLE style="FONT-SIZE: medium; FONT-FAMILY: 'Times New Roman'" cellSpacing=0
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<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">Considering the
so-called </SPAN></FONT><I><FONT face=Arial><SPAN class=style9
style="FONT-SIZE: 12px">standard atmosphere</SPAN></FONT></I><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">, the refractive
index is 325 N-units at ground level which decreases by 44 N-units per
height-kilometer [12]. This is also visible in figure 5 when focusing on
altitudes not higher than 1200m. Within a small interval at higher
altitude, the refractive index however drops sharply by 70 N-units which
indeed represents an intense inversion layer. Thus, the height profiles in
air temperature and dewpoint (see figure 2 to 4) indeed indicate major
discontinuities in the refractive index which have certainly affected
radiowave propagation between England/Ireland and the west coast of
Africa. We may speculate that all this inversion layers were caused by
warm air moving over the cold sea water probably supported by calm weather
because no turbulence has destroyed the layer formation and its apparent
persistence during the day (this assumption is supported by all
observatories which indicate low wind speeds of less than 10 knots at
ground level).</SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><B><FONT
face=Arial size=4><SPAN class=style107
style="FONT-SIZE: 14px">Speculations on the radiowave propagation
paths</SPAN></FONT></B><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px"></SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">Having identified
intense inversion layers between 1000m and 2000m altitude, we however
cannot yet explain the true radiowave propagation paths. To explain path
lengths of more than 3000km, tropospheric ducting appears an plausible
interpretation though. Elevated ducts may guide the radiowaves along a
wavelike propagation path through the troposphere and ground ducts, on the
other hand, may reflect radiowaves between an inversion layer and ground -
both scenarios may support long distance propagation on VHF, UHF and SHF
[12].</SPAN></FONT></P></TD>
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alt="Figure 6. Vertical profile of the refractive index N (blue) and its dry (red) and wet component (green) at Camborne on August 7, 2005, 12 UT."
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alt="Figure 7. Vertical profile of the refractive index at Guimar on August 7, 2005, 12 UT."
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<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">Figure 6 and 7
display the vertical profile of the refractive index in the north and in
the south of Funchal, i.e. at Camborne and Guimar, respectively (August 7,
2005, 12 UT). At Camborne (figure 6) the refractive index N shows a sharp
decrease around 1200m altitude but also a sharp increase just below 2000m.
A similar feature, much smaller though, is also visible around 3700m
altitude. Thus, we find a layer of relatively wet air (see A in figure 6)
embedded within two layers of relatively dry air at, say 1900m and 3700m,
respectively, which altogether may act, perhaps, as an elevated wave
guide. It is however believed that this feature did not play a major role
in the August 7 scenario because of two reasons: 1) the radiowaves were
emitted at ground level (note that G4LOH is located close to the Camborne
observatory), i.e. due to the first discontinuity at 1200m the radiowaves
could probably not access any duct in higher altitudes, 2) the refractive
index shows another interesting feature at ground level which appears more
significant and which is also visible in the Guimar data (see B in figure
6 and also in figure 7). This feature appears to indicate a low altitude
inversion layer that has formed just above the sea
surface.</SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">We may speculate
that this meteorological feature has supported the generation of a
waveguide between sea level and 1200m altitude enabling long distance
communication from England down to the west coast of Africa. It appears
remarkable, that the same feature is visible in two places separated by
2600 km, i.e. at Camborne and also at Guimar, it is not visible at Funchal
though. Nevertheless, this conclusion must be considered speculative and
cannot be verified with scientific conviction. It is also important to
note that the sounding data cannot resolve the vertical fine structure of
the refractive index, i.e. variations of ten meter scale lengths, or so,
cannot be identified at all, those features may however also play an
important role in tropospheric ducting of VHF radiowaves [12]. On the
other hand we may argue, that small scale variations in the local
refractive index can hardly represent constant features over distances of
more than 3700 km, i.e. small scale features must be considered less
important in the interpretation of the August 7, 2005
scenario.</SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><B><FONT
face=Arial size=4><SPAN class=style107 style="FONT-SIZE: 14px">New
awareness for dx links between Europe and west
Africa</SPAN></FONT></B><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px"></SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">The dx scenario from
August 2005 may be interpreted by intense inversion layers between 1000m
and 2000m altitude, open questions however remain in the interpretation of
the radiowaves' true propagation path through the troposphere. And there
is another open question which appears even more important: To the
author's knowledge, intense inversion layers in the sea area northwest and
west of Africa must be considered an usual rather than an extraordinary
phenomenon (note, for example, the vertical profiles in figure 4.5 in the
interpretation of the 2003 dx opening between central Europe and the
Canary Islands [1] which displays inversion layers similar to the above
figures 2 to 4). We therefore need to raise the question why this type of
extraordinary dx openings did not occur more often in the past - perhaps,
it did but it was not observed because of a lack of VHF amateur radio
stations in western Africa.</SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">In the past, VHF
radio propagation between Europe and west Africa could not be considered a
subject within the scope of radio amateurs but we may assume that the dx
openings in summer 2005 have changed the radio amateurs' awareness
considerably. This dx openings have been stimulated by two major
achievements in amateur radio: 1) maritime mobile dx operation has
significantly increased in recent years, i.e. we may now study ocean
radiowave propagation paths which provide dx opportunities not available
on the continents; 2) the Dubus Beacon Project has deployed VHF radio
beacons in strategic geographical positions supporting permanent dx
observations to islands in the Atlantic Ocean and to places on the African
continent. From this perspective, the August 2005 dx QSOs may have an
importance beyond our present understanding. In ten or twenty years or so,
we will possibly consider the summer 2005 dx scenario the door opening
event to new experiences in terrestrial VHF long distance radiowave
propagation in amateur radio.</SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><B><FONT
face=Arial size=4><SPAN class=style107 style="FONT-SIZE: 14px">Vision or
speculation?</SPAN></FONT></B><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px"></SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">In fact, we cannot
exclude similar dx openings in the future, e.g. between coastal radio
stations in western Europe and, say the Cape Verde Islands extending the
IARU region 1 record in tropospheric dxing beyond 4000 km, perhaps (this
speculation has been raised by other radio amateurs too, see, e.g., [4]).
To fire your imagination: in 1996, an Australian 144 MHz radio beacon has
been observed on Reunion Island (Indian Ocean) corresponding to a distance
of more than 6000 km, see [1] and the references cited therein. Can we
have similar dx openings in the Atlantic Ocean too?</SPAN></FONT></P></TD>
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<TD rowSpan=4><IMG height=303 alt=FdNoronhaN29080512UT
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<TD rowSpan=3><IMG height=288 alt=PYislands
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<TD><IMG height=1 alt=""
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width=1 border=0 NOSEND="1"><BR><IMG height=222
alt="Figure 8 (left). Speculative dx paths from England to the Brazilian islands St. Peter and Paul (6000 km) and Fernando de Noronha (6500 km), respectively."
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/objekt1a1a1a1a.gif"
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<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">Surprisingly, we may
find two Brazilian islands in an appropriate geographical position, i.e.
the St. Peter and Paul Archipelago (around 6000km) and also the island
Fernando de Noronha (around 6500km measured from the southwest of
England), see figure 8 (both sites are listed, by the way, by the
Brazilian Commission of Geological and Paleobiological Sites
[</SPAN></FONT><A href="http://www.unb.br/ig/sigep/"><FONT
face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">19</SPAN></FONT></A><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px">]). In both cases, the dx path would
cross the same geographical areas which were discussed in this document,
i.e. regions where intense inversion layers may be considered no unusual
phenomenon. The author has discussed the opportunity of VHF dxpeditions in
this part of the world with two experts, i.e. with Flavio (PY2ZX), who has
visited both islands in recent years, and with Joachim (CT1HZE), head of
the above mentioned Dubus Beacon Project: they are both sceptical [16],
[17]. In fact, the St. Peter and Paul islands are rather small without any
significant infrastructure except of a geological research station (see
the </SPAN></FONT><A
href="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/StPeterPaul.gif"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">photo
assembly</SPAN></FONT></A><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">). This is indeed a difficult place for ham radio
operation although dxpeditions, see, e.g., [</SPAN></FONT><A
href="http://www.papays.com/opdx498.html"><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px">21</SPAN></FONT></A><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">] and also local
scientists [</SPAN></FONT><A href="http://www.geocities.com/ps7jn/"><FONT
face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">22</SPAN></FONT></A><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px">] put this islands in the air
already. A better deal is the island of Fernando de Noronha, perhaps (see
the site report in [</SPAN></FONT><A
href="http://www.unb.br/ig/sigep/sitio066/sitio066english.htm"><FONT
face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">20</SPAN></FONT></A><FONT face=Arial><SPAN
class=stil14 style="FONT-SIZE: 12px">]). Volker Ermert, University of
Cologne, has supported our analysis by providing sounding data measured at
Fernando de Noronha on August 15 and 29, 2005. Figure 9 displays the
August 29 data at 12 UT indicating some inversion around 2000m altitude
although its intensity is much smaller compared to figure 5 to 7. The data
does not justify any speculation about the dx openings' true extend into
lower latitudes on August 29 but, nevertheless, it appears remarkable that
signatures of tropospheric inversion layers may be found along the
northern half and also at the southern end of a 6500km path from England
to the central part of the Atlantic Ocean.</SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><B><FONT
face=Arial size=4><SPAN class=style107
style="FONT-SIZE: 14px">Acknowledgements</SPAN></FONT></B><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px"></SPAN></FONT></P>
<P class=style115 style="MARGIN-TOP: 0px; TEXT-ALIGN: justify"><FONT
face=Arial><SPAN class=stil14 style="FONT-SIZE: 12px">I am grateful to V.
Ermert, University of Cologne, Germany, for providing valuable comments
and for providing the sounding data of the station Fernando de Noronha.
Special thanks to T. Campos, University of Natal, Brazil, for providing
detailed information on the St. Peter and Paul Archipelago and to S.
Erasmi and C. Kollatschny, both at University of Göttingen, Germany, for
establishing the contact. I am grateful to F. Archangelo, PY2ZX, and J.
Kraft, CT1HZE, for providing information on ham radio opportunities on the
Brazilian islands in the Atlantic Ocean. I also wish to thank the
University of Wyoming for granting free internet access to the sounding
data and its archives.</SPAN></FONT></P></TD>
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class=Apple-style-span
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class=Apple-interchange-newline></SPAN>
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<P style="MARGIN-TOP: 0px"><B><FONT face=Arial size=4><SPAN
class=style107
style="FONT-SIZE: 14px">References</SPAN></FONT></B></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[1]</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Very long distance propagation in the 144
MHz band</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Grassmann V., DF5AI, Langenohl U.,
DK5YA</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Amateur Radio Propgation Studies web
site</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><A
href="http://www.df5ai.net/ArticlesDL/VLDP_EA8.pdf"><FONT
face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">http://www.df5ai.net/ArticlesDL/VLDP_EA8.pdf</SPAN></FONT></A></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[2]</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">G4LOH 144 MHz blog</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Fern T. J., G4LOH</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><A href="http://www.g4loh.com/"><FONT
face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">http://www.g4loh.com/</SPAN></FONT></A></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[3]</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Ham radio with EI5FK</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Coughlan C., EI5FK</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><A href="http://www.qsl.net/ei5fk"><FONT
face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">http://www.qsl.net/ei5fk</SPAN></FONT></A></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[4]</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Neuer IARU-Region-1
Tropo-Rekord</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Funktelegramm, 3,
9/2005</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[5]</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">IARU Region 1 Tropo-Rekord am 15.08.
überboten!</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Funktelegramm, 26,
9/2005</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[6]</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Tropo Reports, 2m, 70cm and
up</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Schneider W., DJ8ES</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Dubus, 72, 3/2005</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[7]</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Atmospheric
soundings</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">University of Wyoming, Dept. of Atmospheric
Science</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><A
href="http://weather.uwyo.edu/upperair/sounding.html"><FONT
face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">http://weather.uwyo.edu/upperair/sounding.html</SPAN></FONT></A></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[8]</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Observations, remote sensing,
forecasts</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">University of Cologne, Institute for
Geophysics and Meteorology</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><A
href="http://www.meteo.uni-koeln.de/meteo.php?show=En_We_We"><FONT
face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">http://www.meteo.uni-koeln.de/meteo.php?show=En_We_We</SPAN></FONT></A></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[9]</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Tutorial 1: Basics of understanding and
using soundings</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">University of Bristish Columbia, Dept. of
Earth and Ocean Sciences</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><A
href="http://www.eos.ubc.ca/courses/atsc201/A201Resources/SoundingTutorial1/SoundingTutorial1Readings.html"><FONT
face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">http://www.eos.ubc.ca/courses/atsc201/A201Resources/SoundingTutorial1/SoundingTutorial1Readings.html</SPAN></FONT></A></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[10]</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Temperature
inversion</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Wikipedia, the free
encyclopedia</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><A
href="http://en.wikipedia.org/wiki/Temperature_inversion"><FONT
face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">http://en.wikipedia.org/wiki/Temperature_inversion</SPAN></FONT></A></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[11]</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Lesson 4: Vertical motion and atmospheric
stability</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">U.S. Environmental Protection
Agency</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><A
href="http://yosemite.epa.gov/oaqps/EOGtrain.nsf/fabbfcfe2fc93dac85256afe00483cc4/1c9d492b7ccef4fe85256b6d0064b4ee/$FILE/Lesson%204.pdf"><FONT
face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">http://yosemite.epa.gov/oaqps/EOGtrain.nsf/...</SPAN></FONT></A></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[12]</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Wellenausbreitung I</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Grosskopf J.</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">B.I. Hochschultaschenbücher 141/141a,
Mannheim 1970</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[13]</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Allgemeine
Meteorologie</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Liljequist G. H.</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Vieweg Vrlag, Braunschweig
1974</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[14]</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Einführung in die Meteorologie, Band 1:
Physik der Atmosphäre</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Möller F.</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">B.I. Hochschulktaschenbücher 276, Mannheim,
1973</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[15]</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">BeamFinder - radio propagation analysis
software</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Grassmann V., DF5AI</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><A
href="http://www.beamfinder.net/"><FONT face=Arial><SPAN
class=stil14
style="FONT-SIZE: 12px">http://www.beamfinder.net</SPAN></FONT></A></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[16]</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Personal communication
2005</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Archangelo F., PY2ZX</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[17]</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Personal communication
2005</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Kraft J., DL8HZC /
CT1HZE</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[18]</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Personal communication
2005</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Ermert V., University of Cologne,
Meteorological Institute</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[19]</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">SIGEP - Brazilian Commission of Geological
and Paleobiological Sites</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><A
href="http://www.unb.br/ig/sigep/"><FONT face=Arial><SPAN
class=stil14
style="FONT-SIZE: 12px">http://www.unb.br/ig/sigep/</SPAN></FONT></A></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[20]</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">The Fernando de Noronha
Archipelago</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Geological and Paleontological Site of
Brazil - 066</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><A
href="http://www.unb.br/ig/sigep/sitio066/sitio066english.htm"><FONT
face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">http://www.unb.br/ig/sigep/sitio066/sitio066english.htm</SPAN></FONT></A></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[21]</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">OPDX bulletin, internet
edition</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">OPDX 498, February
2001, </SPAN></FONT><A
href="http://www.papays.com/opdx498.html"><FONT face=Arial><SPAN
class=stil14
style="FONT-SIZE: 12px">http://www.papays.com/opdx498.html</SPAN></FONT></A></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[22]</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Saint Peter and Paul Archipelago
DX-peditions</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Serrano R. C., PS7JN, </SPAN></FONT><A
href="http://www.geocities.com/ps7jn/"><FONT face=Arial><SPAN
class=stil14
style="FONT-SIZE: 12px">http://www.geocities.com/ps7jn/</SPAN></FONT></A></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">[23|</SPAN></FONT></P></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">The VHF/UHF DX Book</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">White I. (G3SEK),
editor</SPAN></FONT></P></TD></TR>
<TR>
<TD vAlign=top width=31 height=16><IMG height=1 alt=""
src="http://www.df5ai.net/ArticlesDL/AtlanticTropoAug05/Resources/_clear.gif"
width=1 border=0 NOSEND="1"></TD>
<TD vAlign=top width=721>
<P style="MARGIN-TOP: 0px"><FONT face=Arial><SPAN class=stil14
style="FONT-SIZE: 12px">Radio Society of Great Britain, 1995, ISBN 0
9520468 0 6</SPAN></FONT></P></TD></TR></TBODY></TABLE></TD>
<TD height=1012></TD></TR>
<TR></TR></TBODY></TABLE><BR>-- <BR>António Matias
<DIV><BR></DIV>
<DIV>CT1FFU - CR5A </DIV>
<DIV><BR></DIV>
<DIV><A href="http://www.dxpatrol.com"
target=_blank>www.dxpatrol.com</A> </DIV>
<DIV><BR></DIV>
<DIV>QRV: HF, 6m, 4m,2m,70cm,23cm</DIV>
<DIV>SSB, CW, MGM</DIV>
<DIV>DX, EME, Contest,Sat.</DIV>
<DIV><BR></DIV><BR><SPAN class=311154010-14032011><FONT
face="Meta Correios Portugal" color=#0000ff> Fonte: <FONT face=Tahoma
color=#000000 size=2>ct-comunicacoes-e-tecnologias@googlegroups.com <B>Em nome
de </B>Antonio Matias</FONT><BR> </FONT></SPAN></BODY></HTML>