A friend and I were discussing the K4HD and he said that it
sounds a lot like the K3S. Well, we both agreed that since the
K3S has world class receiver specs, that would not be a bad thing.
I started comparing the information about the K4HD with the K3S
manual and found:
K3S K4HD Feature
8.215MHz ~8MHz First IF
15KHz ? Second IF (if used in the K4)
24 16 ADC width
~30KHz? 122MHz ADC sample rate (WAG for the K3S)
5 2+1 Crystal filters (one empty slot is from a post
on this list.)
Note: In the K4 FAQ there are forward references to a K4HD
section, but I couldn't find it on the web site.
Analysis and wild speculation
Both DSPs and ADC technology have had at least 10 years to
improve between the K3S and the K4. WHile I don't track ADC
tech, DSPs are computers and we all know what has happened in
computers. The basic processors are somewhat faster, and there
are many more cores on a chip. The K4 certain to have taken
advantage of these improvements.
The K3S uses a 32 bit floating point DSP, and I don't see any
reason to change that specification for any of the K4 models.
Not changing means that much of the K3 DSP code should easily
port to the new DSP.
I don't understand how the basic K4 can get good dynamic range
with a 16 bit DAC. The K3's 24 bit DAC seems a better choice,
although getting high speed and wide bit width at the same time
is hard and expensive.
In the wild speculation department, there seem to be several
approaches for the K4HD. (1) Run a K3 like superhet with an
~8MHz IF and digitize that into the DSP. (2) Duplicate the K3's
2nd IF and use the 16 bit ADC at 15Khz. (3) Use a wider ADC at
either 8MHz or at 15KHz. Note that one of the features of the K4
is ease of upgrade to new ADCs.
73 Bill AE6JV
---------------------------------------------------------------------------
Bill Frantz |"Web security is like medicine - trying to
do good for
408-356-8506 |an evolved body of kludges" - Mark Miller
www.pwpconsult.com |
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