[TenTec] A Look at NR

[Sinisa Hristov]

Orion I Noise Reduction Testing
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Tested with NR settings of 1 and 9, firmware V1.373b5.

Testing performed in LSB mode, PBT = 0 Hz, BW = 2500 Hz
Steady input consisting of white noise plus a CW signal at 700 Hz.
A stream of 25 wpm dits was used, dit duration = pause duration = 50 ms.
Prior to each test, NR was "trained" to a different tone to ensure "fresh" operation.

Actual audio files are enclosed, along with waveform and spectrogram displays.

Bandpass filtering action is obvious from spectrograms.
NR forms a bandpass filter around signal.
The bandwidth can be estimated to 500 Hz.

Both views show that it takes around 600 ms for NR to reach a steady state.
Therefore it is unable to follow actual CW code elements, or different parts of speech.
Instead, NR adapts itself to the "average" signal spectrum.

Please go to http://www.geocities.com/va3ttn and download
the first file from the list (OrionNR1.373b5.zip  454,743 bytes)


73,

Sinisa  YT1NT, VE3EA