[TenTec] V2.059 Speech Processing

[Merle Bone]

Ralph K8RYU wrote:
"Tis a fact of life--the more you "process" anything--be it water, cheese,
or audio--the less "natural" it becomes.  The question always is do you
want to make QSO's or be a hi-fi broadcaster."
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One of the outstanding features/functions of the Orion V1.373b5 radio was its very "natural" but effective 
Speech Processing. Unlike some other features, that seem to be of dubious value, speech processing can make a huge difference when Dx'ing in SSB mode. Doug Smith wrote:

"It might seem funny but in a DSP transmitter, it is relatively easy to compute the transmitter's RF envelope before the modulation is even performed! That, in turn, makes it possible to preprocess the audio applied to the modulator to get exactly the same effect as that produced by an RF compressor. See Fig 5. Post-modulation band-pass filtering maintains the desired occupied bandwidth. As the decay time of the compressor is decreased, an RF compressor approaches the behavior of an RF clipper, long known to be the most effective form of speech processing for SSB. In combination with the Orion's transmit equalizer, results are quite dramatic. The reason RF compressors and clippers are so effective is that they increase the average power transmitted. Human voices tend to have high peak-to-average power ratios-- as high as 15 dB. That means a transmitter whose peak envelope power is limited to 100 W may achieve an average power of as little as 3 W. Under such conditions, the Orion's RF compressor may add 10 dB or more to the average power, equivalent to a ten-fold increase in output power. The speech processor achieves this goal without introducing the kind of distortion that harms intelligibility, such as that created by heavy audio compression or clipping."


If you have a power meter that measures average power it is pretty easy to see the increase in average power with the SP on versus off when running V1.373b5 and on V2.059.  However, the SP function in the Orion 1.373b5 did that without "introducing the kind of distortion that harms intelligibility, such as that created by heavy audio compression or clipping." I told Jack Burchfield that V1.373b5 had the best speech processing I had ever heard (I worked as an HF communications engineer for a number of years). I'm not sure what the value added was of going to an envelope versus peak detection for the speech processing but while the results are functional they include much more distortion then the V1 speech processing. 

I can't comment on cheese.
Merle-W0EWM