Ing. Miroslav Gola

Simple system for Monitoring Weather Satellites:

FM Receiver For 134 - 141MHz

(A double conversion superhetrodyne with pll)

Miroslav Gola OK2UGS

IT'S EASY TO CAPTURE REALTIME IMAGES LIKE THIS DIRECTLY FROM SPACE ON YOUR PC!

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UP-MODE-DOWN

Control of function of the receiver RX134141MHz (setting of operating mode and frequency) can be done in one of two manners. The first way is via PC/RS-232/USB – setting of frequency.

The TEST program via RS232 / COM 1 - COM 4

Cable RS232 and connector DB9 (pin 5 = GND)

Cable RS232 and connector Canon DB9 + RS232 to USB converter

The seconds way is follows the setting by the push-button MODE (UP - DOWN) Push-button MODE is functional after switching-on of the receiver and initial test.

Back PCB = button UP MODE DOWN

The following texts are progressively shown on LCD display:

After termination of receiver’s initial test there will be displayed the text "..SCAN WXTOIMG.."

In the mode "..SCAN WXTOIMG.." the receiver RX134141MHz expects at its input RS232 a code from decoding program WXtoIMG. After reception of the code the display show current frequency in the following format – e.g. 137.20MHz:

Program WXtoIMG sends codes only frequencies 137.20 - 137.10 - 137.40 - 137.50 -137.62 - 137.91 - 137.30 - 137.70 - 137.80 - 137.85 MHz.

By pressing of the push-button MODE you switch to another mode "..FIX MAN TUNG.."

... After pressing of the key UP or DOWN the displayed value increases or decreases by one step equal to 10 kHz (mode "STEP10KHZ" in the range from 134 to 141MHz):

By pressing of the push-button MODE you switch to another mode "..SCAN.."

After pressing of the push-button MODE you switch to another mode "..SCAN.." the displayed value decreases by one step equal to in the range from 134 to 141MHz( 134.00-137.10-137.20-137.30-137.40-137.50-137.62-137.85-137.91-141.00MHz):

Scanning is stopped on the current frequency, when the voltage level "L" .. 0 volt appears at the input IC LM567 SQ_OUT. This happens when high-frequency signal of current frequency with amplitude 0,5uV and modulation 2400Hz is present at the receiver’s input.

By next pressing of the push-button MODE you will get from the mode "..SCANNING.." into operating mode "..STEP10kHz.." After pressing of the key UP or DOWN the displayed value increases or decreases by one step equal to in the range from 134 to 141MHz ... 137.50MHz is start frequency):

By pressing of the push-button MODE you switch to another mode "..S-M-OOOOOO.." , for experiments...

By pressing of the push-button MODE you switch to another mode "..SCAN WXTOIMG.." , Program WXtoIMG sends codes only frequencies 137.20 - 137.10 - 137.40 - 137.50 -137.62 - 137.91 - 137.30 - 137.70 - 137.80 - 137.85 MHz.

By next pressing of the push-button MODE you will get from the mode "..SCAN WXTOIMG.." into operating mode "..FIX MAN TUNG..", when the receiver is tuned progressively to the frequencies 137.20 - 141.00 MHz. By pressing the keys UP or DOWN you can set the frequencies 137.20 - 137.10 - 137.40 - 137.50 - 137.62 - 137.91 - 137.30 - 137.70 - 137.80 - 137.85 - 134.00 MHz - 141.00 e.t.c. ...

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