Weather Chart Transmission System; Handling Of The Remote Control - Wavecom W 4010 User Manual

With Morse signals there is only one tone and with no signal the LED display moves to the right. CW keying
should move the display past the middle over to the left-hand side. The frequency for CW is the more or less
standard 800 Hz, which sounds rather low. With interference, adjust the minimum amplitude squelch such
that the display is moved only by the CW tone. Also the audio filter can be adjusted to the narrowest band-
width as necessary.
The transmission of a weather-chart has a typical noise, a noise which one soon learns to recognize. The
transmission is accompanied by a certain movement of the tuning display. Most stations work with a broad-
band shift of ± 400 Hz which causes a larger movement of the display, but a few stations use a narrow-band
shift of ± 150 Hz with resulting smaller display movement.

2.6 WEATHER CHART TRANSMISSION SYSTEM

Weather charts can be transmitted by radio by fixing them to a rotating drum. A light sensor which moves
slowly along the length converting the intensity of reflections into voltages. These voltages are converted in-
to tones which can be transmitted, respectively received.
On the transmit side, the speed of drum rotation is called RPM and the speed at which the sensor moves
along the length of the drum is called Index of Cooperation (IOC).
On the receive side, it is not only necessary to know the RPM and the IOC, but also when a chart transmis-
sion starts and when it ends. This information is conveyed by a series of control tones before and after a
chart transmission.
The first tone in the series is a signal of 300 or 675 Hz and gives the IOC value. This tone continues for 5 -
10 seconds and can be used to accurately tune in the receiver. Following this, the frequencies representing
black and white are transmitted alternatively at a rate of 1 - 2 Hz for a period lasting 30 seconds. This part
of the tone series conveys the RPM and allows the receiving station to synchronize permitting the image to
be printed in the middle of the paper.
Afterwards the transmission of the weather chart commences. The received output can be printed on a
graphics-capable printer via the CENTRONICS parallel print port. Both 9-pin and 24-pin printer can be used
in A4 portrait mode. Since weather pictures are continually printed, the printer must be capable of printing
150 characters per minute.
After the end of the picture, the stop signal is sent. This consists of an 450 Hz tone with a length of 5 sec-
onds, followed by the tone frequency representing black which lasts 10 seconds.

2.7 HANDLING OF THE REMOTE CONTROL

The new Remote Control of the W 4010 enables the communication between the decoder and a computer
(PC/AT) via a serial RS-232- interface. The commands sent by the computer to the decoder will be inter-
preted inside the W 4010 and transposed into the equivalent unit settings.
The PC additionally can receive teletype data via the RS-232-interface, exhibit them on the monitor and save
in a file.
The well-known PC-program RADIO MANAGER for WINDOWS of the company SHOC supports all functions
automatically. The RADIO MANAGER can now remote receiver and decoder, what before only was possible
with the professional W 4100.
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