--- tlogan7@cox.net wrote:
But while I'm
> exploring, two questions come to mind:
> 1)I've paisted below a description of the DSP in
> the Japan Radio NRD-545 receiver. It mentions 40 bit
> floating point processor with 18 bit over sampling.
> The Pro II and the Orion are newer yet use 32-bit.
> In my simple brain I have to ask why is that? How
> much of a difference does this make? I don't pretend
> to understand DSP - so SIMPLE explanations would
> really help:-)
I wouldn't get overly wrapped with figures touting
numbers of bits alone. What ultimately defines a DSP
radio's performance is still its ANALOG design
characteristics. As long as the A to D and is being
fed signals that are within its range of capability it
will do its job. Also consisder that a 18 bit A to D
could possibly be inferior to a 16 bit A to D interms
of noise figure (S/N ratio), IMD, and so on, so
looking at bits alone really doesn't tell you a whole
lot, you really do have to dig deeper. So it is
important to look at the specs of the A to D chip
itself in term of S/N, IMD, and acurracy, not just
number of bits alone. Our radios really push the
technological limits of A to D technology, both in
terms of dynamic range and S/N (and accuracy)
especially at extremely weak signal levels. Once
digitized it is merely a question of how much
horsepower a DSP chip provides irregardless of the
number of bits it actually processes with. However
with the price/performance ratio of 32 bit vs. 16 bit
DSP's today there is no reason not to use 32bit DSP's
anymore, or even two 32 bit DSP's in one radio.
> 2) My Pro II can hear anything my K2/100 and my
> Omni V did and has better ability to narrow
> filters/notch/noise reduction etc. The Pro II does
> not require me to buy additional filters (of a
> design that have been around for years). That makes
> the Orion even further out of my reach. Why does the
> Orion need those filters?
Simple answer is that the Orion doesn't *need* those
optional filters, it will ship with 3 roofing filters
standard vs the *one* 15 - 20KHz wide ones that
everybody else's DSP radios do. The design "age" of
the Orion roofing filters are irrelevant, there has
been negligible change in analog filter technology for
more than 30 years. It's those roofing filters
passband shapes, group delay, and ripple is what will
be relevant, same is true for all the other DSP radios
already out there.
I cannot imagine that 5
> years down the road all DSP radios will still have
> filters in them. After all, most companies are
> trying to get away from such filters because the are
> getting more costly. So why is Ten Tec throwing them
> into the Orion? How much better could it make it
> than the Pro II? Can someone shed some light?
This remains to be seen in the real world once the
Orion actually hits the street. But the 2 extra
*standard* (and narrower) roofing filters should
theoretically reduce the liklihood of the A to D being
fed (or producing its own) IMD products within the
roofing filter bandwidth, again remember that all of
the competition thus far only use one 15KHz (or so)
filter ahead of the A to D. Additionally the A to D
will be fed less noise energy in the narrower roofing
bandwidths. Also consider that broadband noise and IMD
products not digitized won't then need to be processed
in the DSP either. It cannot be overstressed the
importance of feeding the A to D a good clean signal
to begin with, once digitized the signal can only
really be screwed up by bad coding of the DSP itself,
and that is actually correctable by writing new code
(firmware); as long as the radio manufacture
themselves are so inclined to and are proactive in
addressing any issues like that there may be, plus
have field update-ability built into the hardware
design.
> 3) - I cannot figure out if the 516 is a flash in
> the pan, or here to stay, and what the majority of
> users feel about it at this point? Anybody have a
> clear impression there yet?
All radios are a "flash in the pan" to one degree or
another. The 516 targets and fits and certain market
niche, nothing more nothing more, nothing less.
Duane
N9DG
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