739/144 MHz QO-100 RECEIVING CONVERTER

This receiving converter was designed and described by David Bowman G0MRF in his article "G0MRF UHF-VHF Receive Converter for use with a satellite LNB" in open source on AMSAT-UK web site.

If you bought this Converter I guess you know what you will do with it and how to use it. So I

very shortly described this things below.

This converter was designed to use it to receive the signals from modern QO-100 or Es’hail-2 amateur radio satellite. This satellite was put on the geostationary orbit at position 25.9°E. Its uplink frequency is on 2.4 GHz band and downlink frequency is on the 10 GHz band. So the low cost Satellite TV dish (60cm min) with 10 GHz (LO 9.75 GHz) modified LNB can be used to receive its signals. Modification of LNB represents a replacing of 25.000 MHz crystal in LO of LNB to the high stability TCXO of 25.000 MHz. Not all LNB will work there. It needs the modern LNB with PLL synthesizer in its LO.

Using this converter along with the low cost Dongle SDR tuned around 739 MHz or 2 meters band receiver tuned in a range of 144.550 - 144.800 MHz you can receive the signals of narrow band transponder of this satellite.

I am not providing information where you can buy the LNB or how to modify it. Also I can not help you about installation and pointing the dish. This all things you should know and do by yourself.
More information about this satellite, its transponder band-plan and antenna beam coverage you can find in the Internet.

Also on YouTube you find a lot of videos showing how people works with this satellite and their equipment. Just do a search by "QO-100" words on YouTube.

Circuit diagram of the Converter

Top View of PCB

Pinout of the connectors:

J1 - F Connector - IF input from LNB and +12V to the LNB J2 - SMA Connector - 739 MHz output to the Dongle SDR
J3 - SMA Connector - 144 MHz output to the 2 meters band receiver
J4 - 5.5 x 2.5 mm female Connector - Power connector +12V central pin

BE CAREFUL! To avoid damage of the converter to use a power cord with 0.25 - 0.5 A a power fuse on it. Shorten LNB coax cable will cause to burn this fuse so the converter stay safe.

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