Wavecom W 4010 User Manual page 14

is optimally adjusted.
the filter bandwidth is always an
advanand FEC signals. If this is
not desired, then
modes can be selected. LSB or USB
can be programmed
software automatically
the signal polarity.
The BU-ZI key switches between RTTY
letters/numbers should this happen
to be false. The switch causes no
signal interruption,
effective when a signal is actually
being received.
s o f t w a r e i s
synchronize without
ISS Information Sending Station
IRS Information Receiving Station
The WAVECOM software always decodes the Information Sending Station.
The Sitor/Amtor 7-bit alphabet uses a 3:4 mark to space ratio, however it
is not identical to the alphabet No. 3.
- The Baud rate is always 100 Baud, i.e. 10 ms bit length.
- The ISS sends 210 ms blocks of 21 bits.
- The IRS sends 70 ms acknowledgement pulses.
- The two IRS acknowledgement pulses, called CS1 + CS2, confirm
error-free
reception; the repetition of the same control character tells the ISS
to repeat the last block, respectively the last 3 characters.
- If the ISS does not receive an acknowledgement, it sends an RQ block.
- The following illustrates the transmission mode of both stations:
ISS 123456712345671234567
IRS
<————— 210 ms ——————>
This mode is defined in CCIR Rec.
476-3, Mode B, and is a round table
o p e r a t i o n
acknowledgement to the transmitting
station. The SITOR FEC has two ways
of ad d re s sin g
stations: one
mode which transmits
stati ons , the
selective mode which transmits to
only one station.
consists of a continuous 100 baud
Narrowing
one of these
since
recognizes
but is only
The optimum
a l s o a b l e
the specially
1234567
<70 ms>
w i t h o u t
t h e re c ei v in g
is the collective
to many
other is
This mode
t r a n s m i t t e d
r e p e t i t i o n .
synchronization
choose
collective.
the
Sitor is a simplex ARQ system where
both stations alternately send on
the same frequency. The CCIR Rec.
476-4 defines a period of 450 ms
and the two stations are called:
tage when strong, nearby signals or
interference
s i g n a l .
FEC synchronization
t o with both ARQ and FEC.
123456712345671234567
<—————— 210 ms —————>
data stream with the Sitor alphabet
and the shift is standardized at
a n 170 Hz.
Each character is sent twice with
the second
35 bits
error-free
the output.
errors then the special character
"_" is
recognition.
l i n e e n d
T h i s
without
FEC-selective
disturb the
I n a u t o m a t i c
can be
transmission
after the first.
characters
If both characters
used to indicate
Page 14
R q - I d l e
e n a b l e s
having to
and FEC-
desired
m o d e ,
achieved
following
Only
reach the
have
error