[Elecraft] roofing filter questions

[Jack Smith]

>  
>
> Questions came up in a discussion with a friend of mine who is considering
> the INRAD roofing filter mod for his Kenwood TS-950SDX. He operates almost
> 100% CW, and doesn't hear any IMD products. His beef is noise from stations
> that are just outside the passband of his cascaded IF crystal filters. He's
> hoping the roofing filter will increase the selectivity of the radio.
>
>
>  
>
> 73, Dick WC1M
>
>  
>
>   
Dick:

The question is the source of this noise - it could well be reciprocal 
mixing from the 1st LO in which case no post-mixer filtering is going to 
fix the problem. This is exactly how reciprocal mixing appears to the user.

Until the noise origin is pinned down, it's not possible to state with 
certainty that a narrower high IF  filter will do anything.

Jack K8ZOA
www.cliftonlaboratories.com