[Elecraft] Re: AGC Design of the K3

[wayne burdick]

The K3 selects a filter based on the user's WIDTH setting, which 
usually varies with the mode of operation. Typically you might select 
50 Hz to 1000 Hz WIDTH while using CW mode. We offer several crystal 
filters in this range (200, 250, 400, 500, and 1000), and if you have 
more than one installed, the K3 will select the optimal one 
automatically.

The idea of a variable-passband crystal filter is that it could replace 
two or more fixed-bandwidth filters. For example, if we made one with a 
BW of about 200-500 Hz, it could replace up to four crystal filters (in 
practice, it would be replacing two or three at most). This would free 
up one or two slots for other fixed- or variable-bandwidth SSB filters.

Since this variable-passband filter has 8 steps of bandwidth, we can 
optimize automatically it to be equal to or just a bit higher than the 
selected DSP bandwidth (i.e., the WIDTH control setting). So you could 
think of them as "DSP-tracking crystal filters."

Wayne
N6KR

On May 12, 2008, at 7:23 PM, Shane White wrote:

>
> Wayne, I don't understand the concept of variable passband filters. 
> Surely
> the K3 will just choose a filter based on the current operating 
> frequency,
> and that filter will be used over a range of frequencies. How are 
> these new
> filters you describe different?
>
>
> wayne burdick wrote:
>>
>>
>>
>> 3. Later this year we'll be offering variable-passband crystal filters
>> that each cover a significant bandwidth range, e.g. 200-400, 400-800,
>> etc. (These are not finalized.) Each of these filters will have 8
>> discrete bandwidths. As you adjust the DSP controls, the K3 will again
>> optimize the passband of the selected filter.
>>
>> 73,
>> Wayne
>> N6KR
>>
>>
>
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