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Inmarsat-C works great (with 18i Firmware) !

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  • ham_dj0my
    Hi folks, back around March I reported here that i was getting many CRC errors on Inmarsat-C. I was assuming phase noise problems as an psk modulation analysis
    Message 1 of 1 , Nov 15, 2011
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      Hi folks,

      back around March I reported here that i was getting many CRC errors on Inmarsat-C.

      I was assuming phase noise problems as an psk modulation analysis tool showed significant jitter on the signal and not a clean 180 deg. PSK signal and the psk demodulator was getting out of sync frequently.

      Back then this was with an older FCD firmware version (do not recall which version)

      Now I've just set the dish up again and uploaded FCD with the firmware 18i, which was provided in order to fix a firmware sampling error, which may have caused phase jumps (see other reports here).

      Result:
      Decode is now perfect !!!
      No CRC errors or skipped packets at all.
      Its running fine here since 2h.

      Equipment is:
      Old 60cm TV dish (free of charge from the trash)
      Homemade 3 turn LHCP helix made from old piece of copper wire and the reflector plane is an old scrap piece of PCB...

      With FCD directly at the feed I get around 15-20 dB SNR, wich allows easy decode. This way I pointed the dish, with the notebook right next to it. No preamp needed for this setup - really "el cheapo" !

      However, I use the FCD in the shack and in this case a preamp at the feed is a must. My homebrew single stage GaAS-FET preamp gives me here in the shack around 20-25 db SNR (as read on HDSDR FFT) - which is a real solid signal for such a small dish.

      Try it yourself - you will be amazed.

      Best 73,

      Oscar, DJ0MY
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