[Elecraft] KFL1-4-Band Combinations

[Tom Hammond]

Hi Martin:

>I think I know the answer to this already but just in case, is it possible 
>to configure a 4-band K1 filter module for 80/40/20/15m. I know that pairs 
>of bands share some of the L & C components and maybe 80 & 40m are too far 
>apart in freq for it to work. I work mainly 80/40m on a 2 band module but 
>find it a bit tedious to swap to the 4-band module only to find that 20m 
>is dead and have to swap them back again, but maybe I'm just getting lazy 
>in my old age hi.

It's not only the frequency spread of 80/40, but also that the two ADJACENT 
bands must NOT be harmonically related (ar are 80/40). The filter must have 
a cutoff frequency BELOW the 2nd harmonic of the LOWER of the two bands in 
the pair. As a result, if you tried an 80/40 combination, any 2nd harmonic 
energy of 80 would be INSIDE the passband of the LPF and would not be 
attenuated.

Cheers,

Tom Hammond    N0SS