[Elecraft] Crystal Filter Offset in 4.81, What does it mean?

[Joe Subich, W4TV]

On 2/5/2014 9:55 AM, Brian Alsop wrote:
 > I should also point out that his shows no measurable effect on the
 > 250 and 200 Hz filters.

It will if you choose a 300 Hz offset and Pitch less than 425 Hz for
the 250 Hz filter or a 300 Hz offset and pitch less than 400 Hz for
the 200 Hz filter.

One will see effects due to staggering the IF and DSP filters if the
selected Pitch is less than [Offset + (IF Filter width)/2].

73,

    ... Joe, W4TV


On 2/5/2014 9:55 AM, Brian Alsop wrote:
> I should also point out that his shows no measurable effect on the 250
> and 200 Hz filters. 400Hz and wider are impacted.
>
> On 2/5/2014 14:37, Brian Alsop wrote:
>> Guys,
>>
>> I ran a sweep of the filter response with a 400 Hz filter at nominal 0.2
>> and 03.
>>
>> I have the plot but can't post here.
>>
>> In short the left side of the filter response is moved to the right. The
>> right side moves slightly inward as well.
>>
>> The net effect is a narrowing of the filter -6db bandwidth and also a
>> small shift in center frequency.
>>
>> Here are the numbers:
>>
>> BW (-6dB) =380 Hz, center 485 Hz @ 0.2
>> BW (-6db) =300 Hz, center 508 Hz @ 0.3
>>
>> It appears if you do this, you might also have to adjust the filter
>> offset to bring the center of the passband back to the nominal pitch
>> value.
>>
>> 73 de Brian/K3KO
>>
>> On 2/5/2014 13:40, Mike K2MK wrote:
>>> I installed the 4.81 beta firmware and I am able to change the crystal
>>> filter
>>> offset as described in the firmware notes. I can hear slight
>>> differences in
>>> a CW signal between 0.1, 0.2, and 0.3 KHz. What I don't understand is
>>> what
>>> does it mean. Previous to this release I would have assumed that the
>>> crystal
>>> filter is centered on my chosen CW pitch suggesting a 0 KHz offset. If I
>>> choose one of the 3 offsets am I now listening (and transmitting)
>>> slightly
>>> off zero beat. Why would I want this? Wouldn't I also want a 4th
>>> choice of 0
>>> KHz?
>>>
>>> Explanations in layman's terms would be appreciated.
>>>
>>> 73,
>>> Mike K2MK
>>>
>>>
>>>
>>> --
>>> View this message in context:
>>> http://elecraft.365791.n2.nabble.com/Crystal-Filter-Offset-in-4-81-What-does-it-mean-tp7583674.html
>>>
>>>
>>> Sent from the Elecraft mailing list archive at Nabble.com.
>>> ______________________________________________________________
>>> 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
>>>
>>>
>>> -----
>>> No virus found in this message.
>>> Checked by AVG - www.avg.com
>>> Version: 2012.0.2247 / Virus Database: 3684/6563 - Release Date:
>>> 02/05/14
>>>
>>>
>>
>>
>>
>> -----
>> No virus found in this message.
>> Checked by AVG - www.avg.com
>> Version: 2012.0.2247 / Virus Database: 3684/6563 - Release Date: 02/05/14
>>
>> ______________________________________________________________
>> 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
>>
>>
>> -----
>> No virus found in this message.
>> Checked by AVG - www.avg.com
>> Version: 2012.0.2247 / Virus Database: 3684/6563 - Release Date: 02/05/14
>>
>>
>
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 2012.0.2247 / Virus Database: 3684/6563 - Release Date: 02/05/14
>
> ______________________________________________________________
> 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
>