[Elecraft] [K3] Roofing filters are misunderstood

[Phil Wheeler]

At least I do, Arie. Maybe those with fewer 
"local" signals do not.  Dunno.

Phil w7ox

On 5/12/14, 9:23 AM, Arie Kleingeld PA3A wrote:
> 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).