N8LP's LP-100 has a function for evaluating
Peak to Average performance of speech processors. SSB
isn/t of much interest to me until 10 meters comes back
so I haven't played with this mode in the LP-100. Larry
has a K3 on order and maybe he will compare the K3
speech processor to others when he gets his K3.
73, Bill W4ZV
See LP-100 at
http://telepostinc.com/* Peak to Average ratio screen. Allows accurate checking
and setting of compression in your speech processor.
Peak-to-Average Mode
This mode lets you determine the average power in a signal by taking
40,000 samples/second, and compares this to the peak power in
the signal. The result is displayed as a ratio in dB. I provide a
couple test tones, which are available on my website at
http://www.telepostinc.com/Files/two-level-tone-loop3.zip and
http://www.telepostinc.com/Files/loud_tone.zip. The loud tone is used to
set the maximum power and proper ALC range (with processing OFF). The
two-level tone is used to determine the peak-to-average
ratio of the output signal. It can be played back on your PC, or
converted to mp3 and played on a portable player. It can be played over
a speaker into the microphone, or directly into the mic input. The
two-level tone provides alternating loud and soft tones with 20 dB
difference in level. This tone should provide the following
Peak-to-Average ratios vs. effective compression ratio.
Compression Ratio Peak-to-Average Ratio
0dB 5.2dB
5dB 5.6dB
10dB 3.6dB
15dB 2.2dB
20dB 0dB
I plan more test tones with different characteristics in the future,
which is why I decided to keep the display as Peak-to-Average as
opposed to Compression, which would only be accurate with one test
signal. I will provide additional tables such as the one above with
the additional test signals
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