DOWN CONVERTER 1691 - 1694,5 MHZ


The following text is meant for advanced hams and it describes assembly....


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    Simple dowconverter for Meteosat receiving is described in this article. The main advantage is that you downconverter doesn't contain the chain of multipliers and you need only digital multimeter to adjust it. The downconverter doesn't contain winded coils and all filters are notune made on PCB.

    Converter has low noise figure and high gain. The minimum usable dish size is 60cm. You can use this downconverter with small antenna, with common 144MHz transceiver allowed WBFM mode, with PC sound card and new program JVcomm32. I use YAESU FT-50. These facts could approach weather pictures from sky to wide group of radio listeners. At the end of this article reader will find inspiration how to make this downconverter more cheaper and easier with new Motorola's RF components.

    The system of weather satellites was explained in lot of literature. The most interesting satellites for weather prediction are geostacionary ones. Meteosat 7, usable in Europe, transmits WEFAX data on two channels on 1691 MHz and on 1694.5MHz. If you want to use common receiver for FM "meteo" band you need to convert signal from 1691 MHz to 137.5 - 141 MHz. This is work of downconverter...


Basic description of technical parameters of converter:

 Module input frequency:  1691 - 1694,5 MHz
 Module output frequency:   137,5 ( altern. 155,0 or 58,7) MHz
 Power supply:  DC 9 - 12 V (from receiver's input) 
Current consumption:  270 mA, PTC temperature stabilisation 
Noise number:   < 1.5 dB
 Gain:  40 dB
 Input VF connector:  BNC Fem.
 Output VF connector:  BNC Fem.
 Module dimensions:  95x70x25 mm

Connections side diagram of converter printed circuit...

Component side diagram of converter printed circuit...


In conclusion we solder thermostat according to picture: 

Place the quartz horizontally, pass strip of insulating tube over it and slip under it a target of PTC thermistor. Solder the quartz case to the earthing foil, by which you will connect one contact of thermistor. 


Picture on the left shows procedure for assembly of thermostat for the quartz 24,274437 MHz with use of PTC thermistor and a shrink-wrap insulating tube. Picture on the right shows how to build it into the converter and connect to the power supply of +12 volts...

Further Pictures 













The Art of Improvising... (receiving  Meteosat 7 ... , no problem :-)



As you can see at the last two photos, it is possible to receive signals from the satellite METEOSAT 7 with use of the described converter even behind the window with double glass on parabolic antenna with diameter of 60 cm and without pre-amplifier. 



Complete schematic you will find here (PDF 180KB)   Components layout, top side (bot PCB)  

You can order the kit with very detailed assembly instructions and with rich photo documentation of details and complete unit on CD-ROM at our address:

  Ing. Miroslav Gola - EMGO, Areal VUHZ, a.s., Dobra 240, CZ-73951 Dobrá, Czech Republic 

[email protected]   or   [email protected]


You can view current topical information on internet site of the company EMGO...


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