Conditions:
Run #1: PRO, ACC1, WIDE. Po =100W (0 dBr) at fo = 1000 Hz. | ||||
f1 (Hz) | f2 (Hz) | Po (W) | dBr | OBW (Hz) |
63 | 2934 | 50 | -3 | 2871 |
51 | 2948 | 25 | -6 | 2897 |
40 | 2968 | 10 | -10 | 2928 |
33 | 2980 | 5 | -13 | 2947 |
Note: Further testing has revealed no substantive difference between the PRO and PRO2 for ACC1 transmit audio input. |
Run #2: PRO2, ACC1, WIDE. Po =100W (0 dBr) at fo = 1000 Hz. | ||||
f1 (Hz) | f2 (Hz) | Po (W) | dBr | OBW (Hz) |
64 | 2933 | 50 | -3 | 2869 |
52 | 2948 | 25 | -6 | 2896 |
40 | 2970 | 10 | -10 | 2930 |
33 | 2981 | 5 | -13 | 2948 |
Run #3: PRO2, MIC, WIDE. Po =100W (0 dBr) at fo = 1000 Hz. | ||||
f1 (Hz) | f2 (Hz) | Po (W) | dBr | OBW (Hz) |
96 | 2935 | 50 | -3 | 2839 |
85 | 2953 | 25 | -6 | 2868 |
72 | 2977 | 10 | -10 | 2905 |
65 | 2986 | 5 | -13 | 2921 |
Run #4: PRO2, ACC1, MID. Po =100W (0 dBr) at fo = 1000 Hz. | ||||
f1 (Hz) | f2 (Hz) | Po (W) | dBr | OBW (Hz) |
260 | 2733 | 50 | -3 | 2473 |
243 | 2747 | 25 | -6 | 2504 |
220 | 2770 | 10 | -10 | 2550 |
205 | 2783 | 5 | -13 | 2578 |
Note: These results are fairly close to ITU-R Recommendation M.1173 (350 ~ 2700 Hz @ -6 dB). |
Run #5: PRO2, ACC1, NAR. Po =100W (0 dBr) at fo = 1000 Hz. | ||||
f1 (Hz) | f2 (Hz) | Po (W) | dBr | OBW (Hz) |
462 | 2730 | 50 | -3 | 2268 |
446 | 2744 | 25 | -6 | 2298 |
422 | 2766 | 10 | -10 | 2344 |
406 | 2777 | 5 | -13 | 2371 |
Low-end response for ACC1 Pin 4 vs. MIC input.
With reference to Runs #2 and #3, it will be seen that in the WIDE setting, ACC1 Pin 4 yields -6dB points at 64 ~ 2868 Hz, as compared to 85 ~ 2868 Hz for MIC input. This difference is a function of the high-pass filter in the speech-amplifier circuit. Read Adam, VA7OJ's notes on the transmit audio inputs.
Effect of compression on occupied bandwidth:
Previously-conducted tests have shown that the COMP function increases the occupied bandwidth by about 100 Hz. This increase is due to the signal-level-following action of the COMP function. As the signal is reduced near the edges of the passband, the COMP amplifies it back up, thereby slightly raising the skirts on both ends of the spectrum. I monitored the output signal on the scope using the MONITOR at all times, and could never see any obvious distortion of the sine-wave output signal, even with very high input audio levels. The output power held steady at 107W over a wide range of input levels.
Compression and PSK31:
Using a PSK31 two-tone input signal, the COMP produced serious flat-topping distortion for any power output over about 25W average on the Bird 43. I have previously found that best IMD is obtained for PSK31 with the PRO operating at 40W PEP or 20W average with the PSK31 idle tone excitation.
Copyright © 2002/2003, George T. Baker, W5YR
Page created by A. Farson. Last updated: 06/15/2018