Selection of a contest site for the year 2004
0. Introduction
A good location is key for
succes on the microwave bands. Nowadays free software and digital
terrain databases are available that enable to choose contest sites in
a qualified manner, or at least validate the sites you are currently
using. A small example is presented here.
1.
Measurements
A region survey retained 5 sites for
further study. During a subsequent site visit (Jan. 2), the coordinates
were fixed using GPS, and cross-referenced on the topo map. All GPS
fixes were excellent, indicating a good radio horizon, with device
errors typically smaller than 10m.
longitude
|
lattitude
|
maidenhead
|
height (WGS84)/topo/RM
|
description
|
ref
|
E 4 48 42.79
|
N 50 57 25. 86
|
JO20jw
|
50/55/51
|
off highway
|
1
|
E 4 49 50.37
|
N 50 58 50.9
|
JO20jx
|
47/50/47
|
aureliustoren
|
2
|
E 4 52 25.86
|
N 50 53 35.68
|
JO20kv
|
90/92/87
|
lubbeek
|
3
|
E 4 49 54.42
|
N 50 52 56.65
|
JO20jv
|
87/90/83
|
lubbeek center
|
4
|
E 4 53 14.78
|
N 50 55 9.75
|
JO20kw
|
80/83/81
|
old contest site
|
5
|
The map below shows
the relative positions:
2. DTM data
To allow for a quantification
of site quality, the sites were analysed using Radio Mobile. To
illustrate the quality of the new SRTM height data as
gathered by the Space
Shuttle Reflectometer, the SRTM height is also shown in the table
above.... amazing
isn't it.... a free and accurate Digital Terrain Model! Below is the
regional DTM snapshot, the grid shows the last 2 digits of the
Maidenhead locator (about 4.6km by 5.8km in size):
Here is the same picture but
multiplied with positional references as provided by MapBlast (thank
you Internet). This makes the interpretation a lot easier.
3. Analysis of the
radio horizon
A first analysis that can be
performed is the calculation of the Height Above Average Terrain
(HAAT). This indicates the apparent free height of the antenna. For
these calculations, a mast height of 10m was assumed. The results are
in the table below (estimates based on available DTM data in the square
region of the figures):
longitude
|
lattitude
|
maidenhead
|
HAAT (m)
|
description
|
ref
|
E 4 48 42.79
|
N 50 57 25. 86
|
JO20jw
|
24.5
|
off highway
|
1
|
E 4 49 50.37
|
N 50 58 50.9
|
JO20jx
|
24.8
|
aureliustoren
|
2
|
E 4 52 25.86
|
N 50 53 35.68
|
JO20kv
|
52
|
lubbeek
|
3
|
E 4 49 54.42
|
N 50 52 56.65
|
JO20jv
|
44.2
|
lubbeek center
|
4
|
E 4 53 14.78
|
N 50 55 9.75
|
JO20kw |
50.2
|
old contest site
|
5 |
Clearly the sites on top of
the higher hills perform much better.
Next a single polar radio analysis was performed to assess the quality
of the sites depending on the direction. A network on 10 GHz was used,
with TX +40dBm, RX -127dBm and 20dBi gain antennas as charateristics.
These are just numbers to get a nice graph, and do not describe contest
stations in a good way. One can do path analysis in Radio Mobile too,
by the way. Top left corner includes a DTM and road map of
Belgium referenced to the same coordinates as the analysis graphs. As
can be seen, the Hoge Venen - Hautes Fagnes are within reach of this
small set-up.
ref
|
site 1
|
site 2
|
site 3
|
site 4
|
site 5
|
Clearly sites 1 and 2 are not
as good as the other sites, as expected. Site 4 is not good to the
west. The slope of the hill goes up in that direction. Choosing between
3 and 5, the current contest site is difficult. The current site seems
good to the UK and PA, but is more spotty for DL.
4. Conclusion
As of today, there are no
real reasons to migrate to another site.The one used last year seems to
do fine. Further on-site measurements to differentiate between site 3
and 5 may be needed, but should be done using masts (>10m
height). For the current site, care should be taken to make sure all
masts are above the trees in the direction of North. Maybe this should
be checked with a level. Other sites in the area, around Pellenberg and
Martinusberg, may also deserve further attention.
ON5DRE ON4CJQ ON4QJ
ON4IY
02 01 2004 - http://www.qsl.net/on4iy/eur-site.html
5. Extra
Application of
Radio Mobile as path loss calclation analysis tool. In this case, the
QSO PA0WWM-ON4IY/P is presented (JO22FE-JN29RT). Results were as
predicted!
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