[Elecraft] K3 CW Filter

[Joe Subich, W4TV]

 >  Eg define the 400 filter as if it were 1.4.  Then use a high PITCH
 > setting of 700 to make sure that audio rolloff is not in play.

Or enable the filter and measure the bandwidth in DATA A.  DATA A
will center the filter at 1500 Hz and you can make the DSP bandwidth
up to 4 KHz.

73,

    ... Joe, W4TV


On 9/25/2010 6:39 PM, Guy Olinger K2AV wrote:
> Make sure you're not trying to measure the 400 filter offsets with the DSP
> set to 400.  To measure the filter offset correctly, first define the filter
> "too wide" in the K3 utility.  Eg define the 400 filter as if it were 1.4.
> Then use a high PITCH setting of 700 to make sure that audio rolloff is not
> in play. Make sure that MENU:RX EQ settings are all at zero.  Be sure the
> AGC is OFF for your measurements and use ATT.  Adj SHIFT until the FC value
> shows a *0.70. Set WIDTH to 1.20.  Now measure your 6 dB points.  Average
> the two, and offset the filter by that amount.  RECHECK and readjust for any
> leftover.
>
> In my case, to align the roofer rejection skirts to match DSP skirts and get
> max dive on the skirts, I use -30 dB points to set offsets rather than -6 dB
> points.  For me the roofers are all about the steepest possible skirts for
> rejection.  The best matching DSP setting is the one (after setting offset)
> that when you narrow it up changes the -30 to -60. When I've done that THEN
> I measure the -6 dB points and that is my best aligned operating bandwidth
> for that filter.  Add 50 Hz to that WIDTH setting and use that as the filter
> width definition in the K3 utility.  This gives me both a "loose" and
> "tight" setting for that roofing filter.
>
> 73, Guy.
>
> On Sat, Sep 25, 2010 at 1:03 PM, Jim Brown<jim at audiosystemsgroup.com>wrote:
>
>>   It is quite normal for there to be offset in the 8-pole filters. I
>> have three, and they all do. Enter the offsets and be happy.
>>
>> 73, Jim K9YC
>>
>> On 9/25/2010 9:17 AM, SCOTT D ELLINGTON wrote:
>>> I'm just setting up a new K3 (4657), and the 400 Hz 8-pole CW filter
>> (KFL3A-400) seems to have a significant offset.  The 6 dB audio bandwidth
>> (AGC off, internal dBV meter) was 236 Hz, and the center about 100 Hz below
>> the sidetone/CWT.  Setting the offset for that filter to -0.13 put the
>> center frequency within 2 Hz of the sidetone, but only increased the audio
>> bandwidth to 316 Hz.   (ARRL measured 341 for that filter.)   Since the
>> audio bandwidth is still low, I'm guessing the filter bandwidth is less than
>> 400 Hz, in addition to having an offset.
>>>
>>> Any comments or suggestions before I bother Elecraft support?
>>>
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Elecraft at mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>