To share a bit of my findings with the group.
I used a source of broadband white noise with input level held constant. No
change was made other than processor level being changed to obtain the
following values. The power output was measured using a Bird 43P and a
sampling loop to the Tektronics O'scope and Bird 50.5 ohm load. I started
with the SP off and set the levels to produce 2 watts PEP output. Then with
the SP on at 0% I observed that the power was 0.75 watts. As I advanced
the processor level the output level increased in roughly 3 to 4 dB
increments and clearly in steps not related to the actual display of SP
value.
It was noted that in between the steps there is no power change. Case and
point, at values between 18% and 28% the power remained at 2.0 watts.
Between 28% and 29% the power changed from 2.0 W to 3.5 W. The same held
true for other increment of steps. Back some time ago, John Henry confirmed
that there are actually 9 steps in the Speech Processor control algorithm.
Power output = 2 W with SP off
With the SP on the following is observed:
0% = 0.75W or - 4.3 dB
7% = 1.0W or - 3 dB
18% = 2.0W or 0.0 dB
29% = 3.5W or + 2.4 dB
39% = 6.7W or + 5.3 dB
50% = 15W or + 8.8 dB
62% = 40W or + 13.0 dB
73% = 70W or + 15.4 dB ALC is now on and no further increase in SP gain
produced any increase in output power
This seems to indicate that the effective SP value should be about 40% to
50% to attain some 6 to 8 dB of increase in output power. At the same time,
before the SP is activated, the MIC Gain was adjusted to give an occasional
flash of the ALC LED but by no means is solid on during words.
I tried another test which was to increase the audio input level to such,
with the SP off the ALC LED just flickered on and off. Power output was
about 50 watts. With the SP ON and at 0% the output level dropped to 20
watts. Increasing the SP level the power went to 70 watts at 29 to 30% and
stayed there. ALC LED now solid on. This seems to confirm that the ALC is
the controlling factor in PEP output while the SP does add significant
average power to lower level signals.
On air tests with folks with whom I regularly chat have not reported any
ill effects of the SP at values of 50% to 55% except to say the signal is
loud.
73
Bob, K4TAX
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