[TenTec] RE: DIgital Signal Processing

[Ken Brown]

I think that there are some reasonable and logical distinctions that can 
be made between digital control techniques and digital signal 
processing. Most  production radios have been using digital techniques 
for controlling the function of a basically analog radio for many years 
now. When an optical shaft angle encoder drives a microprocessor  which 
then controls a PLL to determine the local oscillator frequency of the 
receiver, this is digital control, NOT DSP. When the received SIGNAL 
gets DIGITIZED and PROCESSED DIGITALLY, this is DSP.

Here is a contrived example of digital control versus digital signal 
processing:

If the radio uses an up/down button to control the volume, and the 
microprocessor is controlling an analog attenuator in the audio path, 
this would be digital control, not DSP.

If the radio uses an up/down button to control the volume, and the 
microprocessor is controlling the volume by performing an arithmetic 
function on a stream of bits that represent the audio, this would be DSP.

 From the outside of the box they appear the same.

DE N6KB


Merle Bone wrote:

>Mario,
>I really don't make much of a distinction between which of the CPUs are
>involved in performing the function digitally. While it is true that the
>general purpose processor has a different instruction set, it is still
>involved in digital control of the radio functions - part of digital signal
>processing. I recommend Doug Smith's book "Digital Signal Processing
>Technology." Doug was the main designer of the Orion. In his book he covers
>this by saying:
>
>"In general, modern DSP systems characterize and modify analog signals,
>producing other analog signals as their outputs. Note that this is not
>always the case, though; the output of a DSP circuit might just as well be
>the opening of a squelch gate or the triggering of a VOX."
>
>Merle - W0EWM
>
>
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