[Elecraft] K3 sub rx matched filters

[Don Wilhelm]

Jeff,

The filter offsets should be set the same for diversity reception, and 
for that to happen most easily, the filters can be matched.  You may 
notice a "wush, wush" sound if the offsets are different.
But being practical, the *difference* between the actual offsets of the 
filters will be within tens of Hz, and for a wide filter (1.8 kHz or 2.7 
kHz), setting the K3 offset values to the average of the two filters 
will work fine.  OTOH, with narrow filters such as those used for CW, 
the two offsets must be closely matched because the difference in the 
offsets is a larger percentage of the filter width, and requires matched 
filters.  It is the difference between the offsets that matters, not the 
actual offset value.

Supposedly, the 8 pole filters do not have to be matched (they do not 
have offset numbers associated with them), but in practice, they may 
have a small offset and some ''tweaking" of the offset values may be 
required to eliminate the "wush, wush" sound when using diversity.

73,
Don W3FPR

jeff kb2m wrote:
>  I'm thinking of upgrading my K3 by adding a KRX3 sub receiver. One of the 
> things I want to try in the near future is diversity reception. Now, I think 
> I need a matched pair of filters to operate in diversity mode? Or does this 
> just pertain to the 5 pole  filters?  Or, if I already have an 8 pole 1.8 
> filter would I just have to buy another one ? I tried to search the archives 
> and there appears to be no keyword search? Thanks in advance for any help 
> with this....
>
> 73 Jeff kb2m
>   
>