[RTTY] K3 filter for rtty?

[Joe Subich, W4TV]

 > Is the 250 Hz 8 pole too sharp?

The 250 Hz 8-pole filter is really 370Hz at -6dB (250 Hz at -1 dB)
- see the curves at http://www.elecraft.com/K3/K3_filter_plots.htm

The 250 Hz 8-pole filter coupled with DSP set to 400 or 500 Hz is
fine for RTTY.  However, I would not spend the money for both a
400 Hz 8 Pole filter or 500 Hz 5 pole filter *and* the 250 Hz 8 pole
filter as the difference between the 400 Hz (435 Hz @ -6dB) and 250
Hz filters is not enough to justify having both.

I am not a fan of the 500 Hz - 5 pole filter.  Having had four of
them (main/sub in a pair of K3s), I find them to have excess ripple
in the passband and poor shape factor (> 3:1 6/60 dB).

I find the 400 Hz filter a minimum useable bandwidth for general
CW operation and would recommend either 500 Hz 8 Pole (from INRAD
- actual bandwidth not specified, estimated 525 Hz @ -6dB) and
250 Hz 8 pole *or* 400 Hz 8 pole and 200 Hz 5 pole for critical CW.

73,

    ... Joe, W4TV


On 2014-08-21 8:53 AM, Jerry Pixton wrote:
> Fellow rttyers,
>
> If I get a new K3, what filter do I want for rtty? Bandwidth and 5 or 8
> pole? Is the 250 Hz 8 pole too sharp?
>
> My primary operating mode is rtty followed by cw for Dxpeds
>
> Jerry, W6IHG
>