A Web-SDR for the Es'hail-2 satellite 10 GHz AMSAT transponders:



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- designed and prototyped a downconverter scheme for receiving the two AMSAT microwave transponders on the Es'hailsat-2 spacecraft, due to be launch in Q4/2018 (08.08.2018)

- the prototype triplexer separates the L band IF spectra, the 22 kHz control signal (not used), the 27 MHz reference carrier and the 9Vdc for the LNB bias(08.08.2018)

- in this photograph you can see the basic building blocks that you may find in the block diagram (15.08.2018)

- for L band selectivity I retuned a 900 MHz GSM (Finnish Manufacture) helical filter down to the 750 MHz range (08.08.2018)

- the performance is actually quite reasonable with 0.7 dB passband (1dB/div) ripple and a return loss of >18 dB (5dB/div) (08.08.2018)

- after modifying the Octagon Oslo PLL LNB (serial no. 3) for external 27 MHz referencing, the LNB appears original and intact (08.08.2018)

- the modification (photo of serial no. 1) consists of a 12pF and 2.7uH series LC with Kapton tape instulation (08.08.2018)

- I removed the 27 MHz crystal and formed a simple LC bandpass filter (serial no. 3) to route the injected (-10 dBm) external reference directly to the image reject mixer/PLL/IF IC (08.08.2018)

- here is an early IF spectrum and waterfall of the LNB downconverted IF noise (10- 21 MHz) (08.08.2018)

- still three spurs to wok on, but they are all outside the transponder passbands, could also work on the passband flatness (simple case of 50/75 ohm missmatch)

- in the waterfall, the LNB is first seeing Cold Sky (slighly overcast) and then CS + uncalibrated radiated noise from a waveguide noise source

- divider programming for the Bodnar Dual Output GPS Secondary Standard (Thanks to Leo and Simon for figuring out numbers for clean CW/SSB quality LO carriers) (08.08.2018)

- as there are no cross polarisation emissions on the downlink, the initial plan is to simply lose 3 dB and align the PLL LNB at 45 degree offset for both linear polarisations

- it still remains to be seen if there are any issues with cross-transponder IMD and if so, I will simply realign for cross polarisation minimum

- adding a second LNB + 2. converter and multiplexing the two HF IF bands will allow simultaneous monitoring of both transponders - I am very interested in OSI Layer 1 analysis :-)




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Created 08.08.2018, Updated 25.08.2018