[Elecraft] Xtal Filters

[Tony Fegan VE3QF]

Hi Knut and all,
    I totally agree with you. CW operation of the filters is fine. With 
SSB it would be way easier if the filter centre frequency would be 
reduced by a small amount as the width is reduced. In the "heat of 
battle" those small filter knobs are not easy to adjust without nudging 
the VFO (I don't have much feeling in my finger tips).
    I would prefer to use the XFIL button to immediately switch to a 
narrower filter which is suitably centered for SSB reception. With a 
2.1KHz xtal filter the low frequency could be about 250Hz and 350Hz for 
a 1.8KHz filter.
    As this (XFIL button) seems to be the unused button on the K3 maybe 
one or two extra narrower filters for SSB could be setup in DSP with 
appropriate centering. This then would function even if you did not have 
the extra "roofing" filters. It would be way simpler than fiddling with 
those filter knobs. I always thought those knobs should have had a very 
positive detent (a 1/2 in. longer knob would help too). My shaky hands 
don't handle them well at all.

Food for thought.

73
    Tony Fegan VE3QF
    K3 #137

ab2tc wrote:
> Hi,
>
> I am assuming that you are using SSB. For SSB, use the Hi Cut / Lo cut mode
> instead and adjust the Hi Cut for lower bandwidth. The Shift / Width mode is
> not suitable for SSB since it wants to keep the center frequency constant,
> while what you want in almost all cases is simply decreasing the high end of
> the passband, keeping the low cut at 300Hz or so. SSB with a low cut of
> 600Hz sounds extremely bad. For the same reason, I find the XFIL button
> unsuitable in SSB mode since it wants to "center" the new filter which again
> causes the low cut to be way to high. I still think some of the design
> choices for this rig are not optimal for SSB operators.
>
> Knut - AB2TC
>
>
> Evert Bakker (PA2KW) wrote:
>   
>> Hello all,
>>
>>  
>>
>> Today I received the 1.8 Kc 8 pole filter and installed it tonight.
>>
>> I did the configuration with the software tool used for firmware updates
>> as
>> well (also performed an update as well).
>>
>> All went OK, but I do have a feeling something is wrong or my ears/brains
>> work a little different from the majority (yeh yeh I know...)
>>
>> When XFil 2.7 is selected together with the DSP at 2.7 Kc, the audio
>> sounds
>> great. When decreasing the BW with the DSP to 1.8 (but keeping the centre
>> the same), the hardware filter is switched in at 1.8 Kc DSP setting.
>> During
>> the decreasing process I'm loosing "information" (Ofcourse!) but my
>> feeling
>> says too much. When during the decreasing process I also lower the centre
>> freq, the excessive loss of "information" is compensated. This gives me
>> the
>> feeling as if the filter isn't centered anymore.
>>
>> First I thought this might have to do something with the Offset (-0.91 for
>> a
>> 2.7 5 pole filter) but nothing was written on the 1.8 Kc 8 pole filter. I
>> just tried it, but that didn't compensate the excessive loss.
>>
>>  
>>
>> During a process of decreasing bandwidth while listening to an SSB signal,
>> I
>> would appreciate if a shift of the centre-freq of the DSP is not required
>>
>>  
>>
>> Any suggestion?
>>
>>  
>>
>> 73's, Evert PA2KW
>>
>>  
>>
>>  
>>
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>>     
>
>