IC-756Pro II and IC-746Pro: 500 Hz CW Filter Comparison

Contributed by George T. Baker, W5YR
Figure 1. Spectral plots for no-signal, IC-746Pro and IC-756Pro II.
Figure 1. Spectral plots for no-signal, IC-746Pro and IC-756Pro II.

 

Test Criteria:

  1. Signal source: band noise on 50.197 MHz CW with 500 Hz BPF setting.

  2. Peak in-band responses set equal as shown.

  3. Sampling was 88,200 sample/sec with 16,384 FFT samples and a running 500-spectrum average with Hanning smoothing.

  4. Radio input to program via audio-to-USB conversion unit, Edirol UA1A with opto-coupled stereo input and output and 44.1 kHz sampling of 16-bit data.

  5. Filter centered on 700 Hz. Almost precisely 500 Hz wide at the top.

  6. Note that IC-746Pro stopband attenuation is approx. 10 dB better than that of IC-756Pro2. This suggests slight superiority of the newer IC-746Pro code and TI DSP processor (vs. ADI SHARC in IC-756Pro II).

  7. Disregard spikes in 0 ~ 250 Hz region (probably AC mains harmonics).

Copyright  2002, George T. Baker, W5YR
Page created by A. Farson. Last updated: 06/16/2018