[Elecraft] [K3] Roofing filters are misunderstood

[Arie Kleingeld PA3A]

Well,

You defenitely need those filters in the K3.
When signals are strong and the band is busy, signals coming through the 
roofing filter (line S9+20dB) is said to pump the hardware AGC, even if 
you have the DSP filtering set to a small BW. Anyway, you can certainly 
hear that.
Try it on CW,  on 40m in the evening when there's a contest. You'll love 
the 400Hz roofing filter.


73
Arie PA3A




Al Lorona schreef op 11-5-2014 23:03:
> What determines the bandwidth you hear at the loudspeaker? It's not your roofing filter, despite a continuing notion that it is.
>   
> Dave Hachadorian's point in a post a few weeks ago was that you don't need a 1.8 kHz filter to get a 1.8 kHz bandwidth. You're free to set whatever bandwidth you want with any filter.
>
> Before rigs had DSP we got used to the idea that your crystal filter sets your bandwidth. That's not true any more. It sets your *maximum* bandwidth. You then have the freedom to narrow and position a bandwidth arbitrarily using the DSP controls [SHIFT and WIDTH or HI and LO].
>
>
> Here's a true-false quiz:
>
>   
> 1. I'm a contester, so I need a 1.8 kHz roofing filter in the K3.
>   
> 2. I should purchase the 400 Hz filter if I like to operate CW with bandwidths of 300 - 400 Hz.
>   
> 3. For SSB, the 2.7 and 2.8 kHz filters are 'too wide'.
>   
> 4. I have the 2.7 kHz filter installed, so for best results I should set my WIDTH control for a passband of 2.7 kHz.
>   
> 5. I can use my 2.7 kHz filter in CW mode with my LO=0.30 and HI=0.50 (that is, BW=0.20).
>   
>