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Field Aligned Irregularities
Wath is F.A.I
Geometry of F.A.I.
Height of Scatter
The Best Season
The Europe Map
IC8FAX 's experience on the F.A.I
- Page Under Construction -
- Wath is F.A.I -
The F.A.I. (Field Aligned Irregularities) is
due to irregularities E-Layer ionization aligned to the earth magnetic
field. The irregularities E-Layer ionization grows a zone of scatter where
the Vhf emission are reflected. The propagation was short lived and disappeared
when the heaters were turned off.
Several condictions are requiered to establish a F.A.I. radio link:
Suitable ionospheric condictions must be available. Furthermore, a suitable
scatter geometry must be set up by the locations of the transmitter, receiver
and scatterer. In particular both the transmitter's and receiver's antenna
must be directed at a common scatter volume. These requirements were furfilled
for the observations in concern, otherwise these QSO's couldnot have been
- Geometry of F.A.I. -
A radio signal illuminating FAI will be scattered
back to ground in a cone shaped pattern with the apex at the irregularity
and the axis aligned to magnetic field line. The intersection with the
earth of the scattering cone, having an angle a2 to the magnetic field
line, gives the contour of the maximum reception which is also labelled
a2. Contacts may take place between stations located on supplementary countors(their
sum is equal 180 deg.)
- Signal Characteristic -
F.A.I is different from Sporadic E or Tropo for
the following main charatteristics :
- Signal offset from the great circle bearing.
- Rapid flutter, it is similar to auroral propagation in sound, but not
as disruptive. Frequency components of 30 to 100 Hz are tipical. Ssb is
quite intellegible when signals are somewhat above the noise.
With qsos in CW is preferable low speed .
- Heigth of Scatter -
The heigth of E-Layer is about 100-140 Km. Therefore
the proper elevation of the antenna is decreasing with increasing of the
distance of the station from the scatter point.
IW1AZJ Silvio in Turin at 150 Km. distance of the scatter use 35 °
of antenna elevation.
IC8CQF Lino in Island of Capri at 800 Km distance of the scatter use 6°
of antenna elevation.
So the station near the scatter point that do not have an antenna system
elevation could use one fix antenna with a just elevation.
- Known Scatter -
Scatter at Brussels (CL/CK) :
This scatter is non available for me, please send me info about charatteristics
of this point
Scatter at Budapest (JH) :
Scatter at Geneva (DG) :
Scatter at JN92 :
Scatter at JN41/42 :
This scatter is available for me but I have not direct info about this.
Pse EA3ADW send me,tks.
- The Best Season -
The European F.A.I season generally starts at
beginning of May and ends in the middle of September. Openings have been
more frequent from the 16:00-19:00 Utc. In the last 1996 I have worked
many openings, with good signals, betwen 20:00-22:00 Utc. I have had in
the log only 3 stations from France. Usually during the previous seasons
have worked about 45 several station. This is modification of the scatter
point or low activity from France ?
- The Europe Map-
- IC8FAX ' s experience on the F.A.I.
I am located in Capri Island in JN70CN,
my first qso in F.A.I was in the May 1990 with Didier
FA1MXE in JN05GQ
with 100 watts and 17 element Tonna. The scatter point was Geneva
at 330 °.
Now my work conditions are :
Yaesu FT736/R with Mutek Front-End,
Pa Eimac 8930 about 300 watts,
Shark 20 Element long yagi 9.50 mt. boom; 30°
Later on, I have had many qsos in different
scatters points (Geneva, Budapest, Brussels,
JN92) and have worked the following squares
The phenomenon of the F.A.I. is more frequent
in the period within May to September to 16 at 22 utc.
Experience tends to confirm the link
between F.A.I in 144 MHz and sporadic E in the 50 MHz. The opening more
frequent are on the Geneva scatter point,
in June I have worked F.A.I. almost the evening-nitgh. At begin the best
signal is from the West (France, Spain , Italy), at ended the signal
for the Est is still very good. The signal is similar to auroral propagation
in sound. but not as disruptive. Frequency components of 30 to 100 Hz are
tipical. Ssb is quite intelligible when signals are somewath above the
noise. In cw is preferable to use a low speed. When I have listen
the F.A.I with distruptive signals, I have worked some squares not
frequently. The scatter point on the Budapest
is also much famous but on the it thare is not many activity. On the scatter
point in JN92
I have worked only SV1BTR in KM17. JN92
is probably the some scatter point used in the Qso between 5B4/DL5MAE
and IK6EIW and also I5 stations.
The K9SE have developed a programm that help to know
the F.A.I phenomenology. He plot many contours lines ascribe at same scatter
point. The contours represent the mathematical complement af the incident
or reflected ray angle with respect to the scattering axis. When a station
anywhere on the - 5 countor transmits toward the scatter, the reflected
signal returns to earth not at one point, but along the antire arc of the
+5 countor. A station on the 0 degree contour can work any other station
on the 0 degree contour, including itself. (Ref. F. Kneisel K4GFG
QST Jan 1982).
The square IN89
, at 02.09.95 14:46 utc, was probably worked around at the
Brussels Scatter Point,
in fact Allan (
GJ4ZUK ) had his antenna in direction of 80
° , my qtf was 335 °. This square is not ordinary for the my F.A.I
References to :
Beyond line of sight by Emil Pocock
Ionospheric scatter by Field Aligned Irregularities at 144 Mhz by K4GFG
Dubus 3/86- Propagation at 144 Mhz by I3LDS
Dubus 2/88-Is there a Fai scatterer above Budapest ? by DF5AI
Software Fai from K9SE