[Elecraft] adding 250Hz filer, any improvement?

[Joe Subich, W4TV]

The "250 Hz" filter has a nominal -6dB bandwidth of 350 to 370 Hz
(see plots at http://www.elecraft.com/K3/filter_plots/250.gif and
www.inrad.net).   The 400 Hz filter has a nominal -6dB bandwidth
of 430 - 450 Hz (plots at the same sites).

Since the ultimate selectivity is generated by the DSP, *not* the
first IF filter, the difference in protection against strong adjacent
signals would be minimal (less than 50 Hz on either side).  There
would seem to be little practical difference between the two and
no justification for adding one if the other is already fitted.

If one already had the 400 Hz filter, adding the 200 Hz Elecraft
filter (narrower than the "250 Hz" Inrad down to at least -40 dB)
would make more sense.

73,

    ... Joe, W4TV


On 2/8/2011 12:49 PM, Jorge Diez - CX6VM wrote:
> Hello,
>
>
>
> I have both KFL3A-400 (400 Hz 8-pole) and KFL3A-1.8K  (1.8 kHz 8-pole)
> filters in my K3.
>
>
>
> If I add a KFL3A-250 (250 Hz 8-pole) filter I will notice it better to use
> in contests?  Or with the 400Hz is enough?  Notice I am not in USA or EU
> with strong stations near me, I don´t have the QRM this big populations
> have, trying to reduce the splatters.
>
>
>
> 73,
>
> Jorge
>
> CX6VM/CW5W
>
> k3 #4077
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>