opening on 50MHz was very unusual in that it was outside the normal
seasonal times for sporadic E (around the mid-summer solstice with a
minor peak around the mid-winter solstice). The
opening lasted for over two hours during which the centre of reflection
moved very roughly from south-eastern France to south-western France. A picture of the dx cluster is shown here.
Click on the image for a large size version. What this image
doesn't show is the propagation to TA from a number of countries
including OK, DL, HA, I and G. A QSO was made between G4IGO
(IO80nw) and TA2ZAF (KM69kv) around 1621z. The distance is 3009
km, which wouldcouldbe double hop Es but given the weak signal in IO80/81 could also be a combination of single hop Es and tropo.
question of whether it is sporadic E is answered by the Chilton
ionogram, shown here. Click on the image for a large size version.
The image is for 1620z. The presence of a strong Es layer
at about 110km height is visible, together with the multiple 2 and 3
times around reflections.
seen below are ionograms for Pruhonice near Prague (Czech Republic) on
the left (1630z) and Dourbes (Belgium) on the right (1530z).
Strong Es layer reflections are noted at a height of
110km although not at high enough a frequency to support the 50MHz
the opening Ken G4IGO alerted the ON4KST chat to the presence of an
auroral sounding signal from the Spanish TV vision carrier on
48.250MHz. This station is located at Navacerrada (IN70xr).
The signal peaked on a bearing of about 120 degrees initially, slowly
moving to around 150 degrees. The true bearing from IO80NW is 184
The spectrum of the signal is shown here. Again you
can click for larger image. The signal spectrum is about 100Hz wide and
It is speculated that the propagation
here is FAI (field-aligned-irregularity) - due to the auroral sound and
the indirect side-scatter path. This is observed on 144MHz, but
I am not aware that is seen often on 50MHz. The
mode is analagous to Aurora in that the irregularities are aligned
with the geomagnetic field. It is a relatively weak effect, requiring
high power, thus the signal here is not very strong despite originating
from a 250 kW transmitter. A combined Es forward scatter and FAI
side scatter event on 144MHz in June 2007 was described in Dubus
3/2007 and is summarised on the DF5AI website. According to the
VHF/UHF Handbook (2002, p3.3) the mechanism is believed to occur in the
E region and the signal is scattered from a volume often
situated near to the Swiss Alps or close to other mountainous areas at
about the same latitude. The bearing of Mont Blanc (JN35kv) from
IO80nw is 124 degrees.