[TenTec] KB7OEX: a big plus favoring ORION

[n9dg@yahoo.com (Duane Grotophorst)]

--- Tom Rauch <w8ji@contesting.com> wrote:
<snip>
> That's why I won't buy a DSP based radio.
> Performance is poor 
> enough using conventional filters because the filter
> follows too 
> many mixers and semiconductors.
> 

These kinds of shortcomings are not specific to DSP
designs. Any RX that has a ton of mixers will share
these issues. This is precisely why I'm partial to a
direct conversions scheme along the lines of the
Collins 95S-1A. As anyone will tell you a DC RX is one
of the cleanest sounding designs there is, just don't
expect any selectivity. But that is where the
wonderful new world of ADC and DSP come in.

<snip>   
> The last thing I want is a receiver that moves
> selectivity even further 
> back in the system running at frequencies my dog can
> hear so 
> marketing departments can say it is "true IF DSP".

I'm still puzzled why low frequency DSP IF designs are
so frequently derided. With a direct conversion/DSP
scheme the selectivity is moved to being just after
the very first (and only distortion producing) mixer.
No doubt there some other design tradeoffs that would
need to be made. 

> 
> It appears we have been brain-washed by the
> marketing 
> departments into ignoring performance!

No argument from me on this point. But my contention
is that it isn't the DSP design per se that have poor
performance, is is all of the design decisions made 
along the way that set the overall performance limits.

Duane
N9DG



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