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There is a good interest in a high performance input stage. Here is an  
example using a medium power FET following the input filter with asymmetrical  
loading. I will change it to inductive coupling and provide a 2 tone test in a  
few days. The filter can be made with binary switched inductors and  capacitors 
and computer controlled selected  so it will be  tracking. The gain can be 
reduced at the output by looser coupling ,. This is  ideal since the noise figure 
of the A/D converter  is about NF=20 dB and  requires a pre amp . A simple 
band pass .should follow to reduce any  wide band noise.
 
The older tube receivers (the better ones ) had an additional   tracking band 
pass filter between the  pre amp and the mixer, or a total of  4 tuned 
circuits.
 
Such an arrangement will make it unbeatable for a contents operation with  
many high power transmitters around.  

Ulrich 
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