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Sound samples for different types of transmissions (FAX, RTTY, SSTV...)


Preface:

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 you need...

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 above.

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 wave

  • 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 HF-Fax)

  • 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 transmitting frequencies.

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 1" mode.

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