On 28 Oct 2002 at 22:19, George, W5YR wrote:
> Very interesting, Gary, and thanks!
>
> I have made detailed spectral comparisons between the IF DSP filters
> in the ICom 756 PRO, the Kachina 505DSP of similar architecture and
> the Icom 765 with conventional crystal filters. There is no comparison
> whatever between the shape factors and overall shapes of the PRO
> filters compared to any of the others. The PRO filters are
> mathemeticallu nigh perfect in shape and performance. I think that you
> have found that the Pegasus IF DSP filters are not the equal to the
> conventional INRAD filters - that is very surprising to me.
>
If you put things in perspective, I don't think it's at all
surprising that 20 poles of Inrad in a Corsair and the DSP
filtering of the PRO are superior to the Pegasus. It all boils
down to one word..........COST.
In the first place I don't believe TT intended the Pegasus to be
a serious contest radio, and did not design it for that purpose.
In it's day and even today if you discount it's lack of digital
VFO's etc and add 20 poles of Inrad filtering, the Corsair is a
contest radio.
The Kachina and 'PRO both have more DSP horsepower to apply
to the filtering process so they too should be superior in that
regard.
The Pegasus on the other hand at approximately 1/3 the cost of
the 'PRO and 1/2 the cost of the Kachina, uses one 16 bit [I
think] DSP processor to not only do the filtering functions, but
also to control all other digital activity. So it has a limited
amount of time to devote to filtering and then goes on to other
assignments. Only Ten Tec knows if it is maxed out or not. Add
an outboard SCAF or DSP filter and you will be close to the
performance of the other radios and still be under their cost.
The Orion of course is designed to be a contest grade radio and
addresses these matters by giving the receivers two 32 bit DSP
processors and two general purpose microprocessors to take
care of other matters. No lack of horsepower here, and from
the looks of things, it will give Gary's Inrad Corsair a good run
for its money. :-).
-73-
-Lee-
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