Yes I did read this too. But IC-718 and IC-703 came after the IC-746
and still had the conventional filter concept.
--- In ic7000@..., "Oba" <ja7ude@g...> wrote:
Hi,
It reminds me of an ICOM engineer saying in an interview that IC-
746
would be the last transceiver that uses conventional crystal
filters
for IF.
73 de JA7UDE Oba
--- In ic7000@..., Adam Farson <farson@s...> wrote:
Hi Buck,
Yes, the IC-7000 will use DSP filtering in the final IF. This is
the same
technology as used in the IC-756Pro series, the IC-746Pro/7400
and
the
IC-7800.
The ultimate performance of the DSP-IF subsystem - dynamic
range,
noise
floor, filter shape factors, noise reduction etc. is a function
of
the ADC
(analogue/digital converter) which is the interface between the
analogue
RF/IF chain and the DSP. The faster the DSP chip, the better the
filter
shape factors, NR etc. are likely to be. All the current Icom
DSP-
based
radios use a 24-bit ADC and DAC and a 32-bit floating-point DSP.
The 756Pro
series uses the ADI SHARC, whilst the 746Pro and 7800 use faster
TI
devices.
The ADC used in the 756Pro series has a slightly better noise
floor
than
that of the 746Pro. The 7800 uses very high-quality ADC's which
are
rather
costly.
The demands placed on the DAC (digital/analogue converter are
rather less
than those which the ADC has to meet, although the DAC plays an
important
role in setting the dynamic range of the transmitter. The ADC is
the key to
the receiver; if it degrades the incoming IF signal, all that
information is
lost forever and cannot be recovered.
There are a number of articles covering these topics (and
others)
on my Icom
page.
Cheers for now, 73,
Adam VA7OJ/AB4OJ
