[Elecraft] K2 - Low Pass Filter location

[Don Wilhelm]

Phil,

I would place the low pass filter between the K2/100 and the KAT100 in 
any case.
For any LPF to behave properly, it must be terminated in 50 ohms (or 
something close), and that is not realized with the LPF connected on the 
output of the KAT100.

Any low pass filter worth its salt should not create any non-linearity - 
but again, if it is not properly terminated, the cutoff frequency may 
not be where you expect it to be.

73,
Don W3FPR

Phil Kane wrote:
>   At present, I am using the K2/100 to feed a KAT100 antenna
>   tuner.  A 160m-10m dipole is connected to the KAT100 as ANT 1
>   through a low-pass filter and a dummy load is connected as ANT
>   2, controlled from the K2.
>
>   I am in the process of installing another antenna (40m-10m
>   vertical) as my prime antenna and the dipole will be my
>   secondary antenna.  For ease of operation I would install one
>   as ANT 1 and the other as ANT 2. To take advantage of the
>   low-pass filter for both antennas I am considering installing
>   it between the K2/100 and the KAT2.
>
>   My concern is with non-linear components in the KAT100 RF path
>   that would generate harmonics and negate the advantage of the
>   filter. Sampling diodes, as in a SWR bridge, are always suspect.
>   If this is to be a problem, I would have to get a second filter,
>   one for each antenna, which is something that I really don't want
>   to do unless I have to.
>
>   Anyone have words of wisdom based on practical experience?
>
> --
>    73 de K2ASP - Phil Kane
>    Elecraft K2/100   s/n 5402
>
>