Thursday, February 4, 2010

LW & MW SDR

Thoughts are back on 500kHz and 136kHz.
Assume we are going SDR, RX and maybe TX, one rig could serve both frequencies.

Conceptual design:
  • TCXO on 4.1943MHz
500kHz:
  1. 4.1943 / 2 = 2.0972
  2. 2.0972 / 4 = 0.5243 (SDR center frequency)
  3. about 20kHz above the band
136kHz:
  1. 4.1943 / 8 = 0.5243
  2. 0.5243 / 4 = 0.1311 (SDR center frequency)
  3. about 6kHz below the band
In other words, the LW quadrature LO can be directly derived from either I or the Q of the SDR center frequency.

My experience is that (for my computers) 96k sampling works best. The observable ranges would therefore be:
  • 476.3kHz - 572.3kHz for MW
  • 83.1kHz - 179.1kHz for LW

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