[Elecraft] K3 vs. HPSDR Mercury receiver

[Bill W4ZV]

Dave G4AON wrote:
> 
> The explanation from the article is as follows:
> 
> "When noise pulses/spikes pass through a crystal
> filter, the phase response of the filter
> changes, depending on the noise frequency.
> However, when noise pulses/spikes pass
> through an ADC with a linear response, the
> phase response stays the same, because the
> ADC treats them in a linear manner."
> 
> While the K3 is "SDR", it also includes crystal roofing filters which 
> the Mercury does not. My Perseus SDR (which also operates with a high 
> speed ADC for direct decoding - no crystals or mixers) does deal with 
> noisy signals better than my K3.
> 
> Next generation transceivers will not use crystal filters and mixers, 
> they are already appearing and the performance is outstanding.
> 
> 73 Dave, G4AON
> 

Blocking Dynamic Range (BDR) is the weak link of current SDR receivers
(typically 120-125 dB versus ~140 dB in the K3).  That will remain the weak
link until ADCs with higher resolution that the current 24 bits is exceeded. 
BDR is important in multi-transmitter environments or if you are close to a
neighbor (amateur or commercial BC station) that has very high signal levels
(which trigger ADC front-end protection and thus limit BDR).  

Until the BDR of current generation SDRs is improved, we will not see pure
SDR rigs (without crystal filter front ends) be competitive in contest
environments.  

73,  Bill  W4ZV

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