Antenna system memorandum 21-AUG-2019

* With Airspy HF+ Dual Port, a dipole antenna (Nippon Antenna AF-1-SP),
  connected with 10m of S-4C-FB coax and 1-to-2 splitter

* Using or not using FM RF signal splitter did not affect the listening
  quality (aka noise level of the audio output)

* Current measurement results for NHK-FM Osaka 88.1MHz for 384kHz IF
  with -E100 option (100 stages of multipath filter)
  at 1100JST 21-AUG-2019 (with Efu's WaveSpectra):
  - Noise level RMS: -73 to -74 dB (-73.6dB)
  - 880Hz time tone THD: 0.028%, THD+N: 0.242%
  - 880Hz tone RMS: -15.24dB
  - -E100 option CPU usage on Mac mini 2018 3.2 GHz Intel Core i7: ~38%

* Current measurement results for NHK-FM Osaka 88.1MHz for 384kHz IF
  without multipath filter option
  at 1400JST 21-AUG-2019 (with Efu's WaveSpectra):
  - Noise level RMS: -73 to -74 dB (-73.4dB)
  - 880Hz time tone THD: 0.433%, THD+N: 0.918%
  - 880Hz tone RMS: -15.21dB

* Teruhiko Hayashi's measurement results from Dropbox for NHK-FM Tokyo 82.5MHz
  with his FPGA receiver at 1100JST 21-AUG-2019 (with Efu's WaveSpectra):
  - Noise level RMS: -82.5dB
  - 880Hz time tone THD: 0.013%, THD+N: 0.081%
  - 880Hz tone RMS: -14.27dB

