[Elecraft] K3 receiver desensing on CW during contest

[Geoffrey Mackenzie-Kennedy]

Larry N8LP wrote on 24 Februay 2009, at 02:40.
 
> 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.
 
 ------------------------------ 
Larry,
 
You could be right, given an adequate amount of R&D funding and time.
 
When the performance of a state of the art HF receiver using xtal filters
will be surpassed by one digitizing at signal frequency is an open question
I think.. The performance standard in terms of Spurious Free 3rd
Order dynamic range vs. time set in recent years by real HF superhet
receivers using xtal filters, as I know it to be, is:
 
Year     3rd Order SFDR    3rd Order SFDR    Filter     Noise
                @ 2 kHz                In Passband         BW      Figure 
 
1993          110 db                      95 db           400 Hz     8 db 

 2007       122 db approx            115 db           500 Hz     7 db
 
 
So don't put the old horse out to pasture just yet :-)

Sorry to have digressed from the subject matter.
 
73,
Geoff
GM4ESD