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Re: [TenTec] RE: DIgital Signal Processing

To: tentec@contesting.com
Subject: Re: [TenTec] RE: DIgital Signal Processing
From: Martin Ewing <martin@aa6e.net>
Reply-to: tentec@contesting.com
Date: Mon, 16 Aug 2004 13:57:42 -0400
List-post: <mailto:tentec@contesting.com>
I think there is a useful distinction between the various CPUs, and it's important for the Orion.

TT doesn't tell us quite enough about the logical architecture of the Orion, but here's what I've learned so far. The "Sharc" DSP chips do the filtering, detection, and modulation.

But the "Dragonball" processor (Mot 68000 family) handles the LCD, VFO control, the keyer (with jitter), serial I/O, and front panel functions. Most of the firmware problems seem to be in the Dragonball code.

The interesting feature (for me) is that, while the control processor directs the DSP operation, the received audio/IF data are mostly not available to the control processor. (Excepting the spectrum display) This means, among other things, that the LCD can't show a tuning indicator (for FSK or PSK), can't show demodulated digital modes, etc. Also we can't show signal statistics that might help set up the digital AGC. Some of these functions are available in the IC-7800, and hopefully we will see them "trickle down" to us proletarian Orion users. (no flames, please!)

I'd say that control processors, high-level signal processing (codecs), and the user interface is where the real innovation will be in the future, because RF and basic DSP are becoming commodities. Anyone agree with that?

73, Martin


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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