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
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