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Re: [TenTec] RE: DIgital Signal Processing

To: tentec@contesting.com
Subject: Re: [TenTec] RE: DIgital Signal Processing
From: Ken Brown <ken.d.brown@verizon.net>
Reply-to: tentec@contesting.com
Date: Mon, 16 Aug 2004 09:30:18 -1000
List-post: <mailto:tentec@contesting.com>
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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