[Elecraft] Dual PB filter

[Brian Alsop]

Just looked at what this Dual PB filter was doing with SPECTROGRAM.

Set up with a width of 600Hz and a 1.8 KHz roofing filter.  DPB off and on.

The 600 Hz alone has the normal filter passband shape. 
DPB on gives a narrower center filter less than 200 Hz wide and two 
augmented wings down about 30db filling out the rest of the normal 
filter passband.

This explains why DPB sounded quietern to one poster.  I suspect turning 
the K3 width setting to 200 Hz would have the same quieting effect.

73 de Brian/K3KO

David Wilburn wrote:

> It has really saved the day on a couple of RTTY QSO's.  That is the 
> only place I have used it.
>
> David Wilburn
> K4DGW
>
>
> alsopb wrote:
>
>> Anybody out there playing with this feature or actually used it in a 
>> contest?  What are your experiences?
>>
>> Playing with it yielded the following:.
>>
>> 1) Narrower CW filters can't be used (at least not my 400 Hz and 
>> narrower
>> filters).  The wings are outside the narrow filter passband.
>> 2) For me that meant the 1.8KHz roofing filter was used.
>>
>> It seems like that defeats the purpose of having a K3.  In a contest
>> situation, I would certainly like as many rock crusher signal outside 
>> the
>> roofing filter passband as possible.
>>
>> It would suggest one might consider the 1 KHz roofing filter, if you 
>> want to
>> seriously use this option.
>>
>> If there existed some intermediate (say 700Hz) or variable roofing 
>> filter, what would it's width have to be to include the wings and be 
>> used for dual
>> PB filtering?
>>
>> de Brian/K3KO
>
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