[Elecraft] K3 receiver desensing on CW during contest

[Alan Bloom]

On Mon, 2009-02-23 at 18:40, N8LP wrote:
...
> I think the days of receivers with xtal filters are numbered. High speed
> ADCs capable of 140dB dynamic range without xtal filtering are on the
> horizon. A 20-bit ADC with enough processing gain would do it. 

I don't think you'll find a 20-bit ADC with a high enough sample rate to
digitize the 3-30 MHz HF band (i.e. >65-70 MHz or so).  At least not at
a reasonable cost.

I believe the best suitable, reasonable-cost ADCs available these days
are able to achieve a 500-Hz blocking dynamic range in the low 120's dB,
maybe 15-20 dB worse than the K3.  That's significantly better than the
previous generation of ADCs could achieve, and no doubt someday we'll
get even better parts that are good enough to challenge the traditional
superhet/crystal filter architecture.  But I don't believe we're close
to that level of performance today.

Another issue, of course, is spurious responses.  I'm pretty sure that
current ADCs don't have good enough spurious-free dynamic range to
challenge a state-of-the-art receiver like the K3.

Al N1AL