Sound samples for different
types of transmissions (FAX, RTTY, SSTV...)
Especially on short wave,
there exists a multitude of stations using a wide variety of different
transmission methods. A lot of these transmissions are furthermore encrypted.
Thus, one cannot tell from just the sound of a transmission, whether
it can be decoded, or not. This does especially apply to RTTY (= Radio
TeleTYpe) transmissions. Please do not waste your time trying to decode
transmissions of Better use a frequency list to quickly find the frequencies
The below sound samples have
all been received under typical receiving conditions. Each sample plays
for about ten seconds. These samples are meant to give you an impression
of what a correctly tuned signal does sound like. The samples are not
well suited as a means for testing JVComm32 or other programs because
for that, they are just too short.
All FAX and RTTY transmissions
on short wave are normally received in single sideband (SSB). Please
keep in mind that if you want to receive a FAX transmission, you must
tune your receiver to a frequency 1.9 kHz below the frequency of the
transmitting station, as it is published in frequency lists, etc. For
RTTY, tune your receiver to a frequency 1.36 kHz below. Both for FAX
and RTTY reception, set your receiver to upper sideband (USB) mode.
As a rule of thumb you can
keep in mind that all commercial stations on short wave are almost always
using upper side band, whilst radio amateurs use lower sideband on frequencies
below an including the 40 m band, and upper sideband on frequencies
Here some samples: (click
the links to listen to the different sounds - Each will open in your default .wav format window)
Weatherfax transmission on short
- Almost all of the weatherfax
(aka HFFAX) transmissions are made using the parameters IOC 576, drum
speed 120. (the corresponding reception mode in JVComm32 is FAX, sub-mode
- Between the different
transmissions which normally last 15 to 20 minutes each, you can either
hear no signaI at all (the transmitter is switched off, or you can
hear a continuous whistling tone)
- At the beginning and the
end of each transmission, some different sounds can be heard. These
signals are used for the synchronization of the receiving station
(your receiver/computer) with the transmitting station.
RTTY weather report transmission
on short wave
- SYNOP-reports are transmitted
using the same method, so one cannot tell from the sound of the transmission
if it is a plain text or a SYNOP message
- Almost all of the RTTY
weather reports on short wave are transmitted using the parameters
baud rate 50 and shift 450 (the corresponding reception mode in JVComm32
is RTTY, sub-mode Baudot 50 / 450)
- Between the transmissions
of the different reports, the station is either switched-off (no signal
at all), or it transmits a so-called CQ-loop, a repeating message
that gives information on the station's call sign and maybe alternative
RTTY weather report transmission
on long wave
- The same applies as for
the short wave transmissions. However, the parameters are slightly
different: baud rate 50, shift 85. (the corresponding reception mode
in JVComm32 is RTTY, sub-mode Baudot 50 / 85)
- The only station known
to me transmitting weather reports on long wave is a transmitter of
the "Deutscher Wetterdienst" running on 147.3 kHz. (tune
your receiver to 145.94 kHz, upper sideband)
- If you have a receiver
that does not tune below 150 kHz, you can probably receive the transmission
of this stations, nevertheless, by using this trick: Tune the receiver
to 150 kHz, select "lower sideband" (!), and in JVComm32,
change the demodulator center frequency from 1360 Hz to 2700 Hz and
klick the "Rev." button. Last, tune your receiver's BFO
or it's passband tuning accordingly.
NAVTEX- transmission on 518 kHz
- Corresponding reception
mode in JVComm32: RTTY, sub-mode: NAVTEX
- Tune your receiver to
516.64 kHz, upper sideband!
- You need to be very patient
when you first start try receiving NAVTEX stations unless you have
a good, stable receiver. The stations only transmit every four hours
for a short period of time. If you have just a simple receiver with
only a BFO and an unprecise or instable frequency display, NAVTEX
reception will become very tricky.
- In the direct vicinity
of the NAVTEX frequency, there are some other stations transmitting
non-NAVTEX signals. Please do not mix up these transmissions with
the real NAVTEX transmissions
- Some weather stations
on short wave are transmitting weather reports using a transmission
mode "SITOR B", sometimes also named "FEC". You
can receive these transmissions using the NAVTEX settings of JVComm32.
Weather satellites - (here: polar
orbiting NOAA satellite in the 137 MHz frequency range
- These satellites use a
transmission mode named "AM-Fax". Please do not get confused
by the letters "AM". You need a FM receiver for the reception
of those satellites. A simple scanner receiver will do, but the results
are normally below optimum because of the too narrow bandwidth of
these receivers. Nevertheless, with a little luck, one can get tremendously
looking pictures with just a scanner receiver.
- A good, external antenna
is a >>must<< for receiving weather satellites since these
satellites have only a very week transmission power.
A vertically polarized antenna is not that well suited since it is
almost "deaf" for signals coming from straight above. You
can find some do-it-yourself proposals for good antennas as well as
a lot of commercial offers on the internet. For more information on
weather satellite reception, have a look http://www.hffax.de.
- The transmission parameters
of the different satellite types (NOAA, METEOR, OKEAN, ...) vary slightly.
In JVComm32, there are different sub-modes defined for the different
type of satellites. The reception mode is always "FAX"
Ham (amateur) radio SSTV transmission
- Most SSTV activity can
be monitored on or in the vicinity of the frequencies 3730 kHz (lower
sideband), or 14230 kHz (upper sideband).
- There exist a lot of different
SSTV transmission modes. Most of them, however, sound very similar
to the above sample. All modern SSTV reception programs (including
JVComm32, of course) detect the transmission mode automatically so
that the user does not have to do any guesswork on what mode to choose.
- The above sound sample
is taken from a transmission that was made using the "Martin