[Elecraft] K3 Filter advice...

[Bill W5WVO]

Don Wilhelm wrote:

> For AM you will need either the 6 kHz or the 15 kHz filter - an AM
> signal will not fit through the 2.7 kHz filter without seriously
> degrading the fidelity.

True enough -- but if you are a SW DXer trying to verify the ID of a weak, 
rare SWBC station, and therefore not particularly interested in fidelity, you 
can listen to AM in USB/LSB mode quite satisfactorily by zero-beating the 
carrier. This is especially cool because by switching between LSB and USB, you 
can pick the sideband that is the least interfered with by adjacent-channel 
signals. Having chosen the sideband to listen to, you can then tailor the DSP 
passband to maximize intelligibility. I use this mode often when DXing on 
broadbanded GC receivers in preference to using the wide AM mode provided.

Bill / W5WVO
K3 in February 2008

>
> The 2.7 kHz filter along with the DSP filtering does an acceptable job
> for casual CW, but if a strong (S-9+30) station comes on the air
> within that 2.7 kHz bandpass, the DSP input can be overloaded, so you
> may want to consider a filter more narrow than the 2.7 - I think 500
> Hz is a good choice.  For data modes, 200 Hz is a good choice, and
> IMHO is a bit narrow for normal CW.
>
> If you are into operating during periods of heavy band use (like
> contest times), then the 8 pole filters with their steeper skirts may
> be helpful, but for more casual use, the 5 pole filters do a great
> job.
> Remember that the filters are 'roofing filters', and not the final
> filtering (which is done in DSP).  Their purpose is to reduce the
> strength of undesired signals ahead of the DSP ADC - as long as the
> DAC is not overloaded, the DSP can provide all the filtering needed. Right 
> now, I have only the 2.7 kHz filter in my K3 and it does quite
> well on CW with only the DSP filtering - but then I have not operated
> on a contest weekend yet either.
>
> 73,
> Don W3FPR
>
> drewko1 at verizon.net wrote:
>> I'm wondering what minimum complement of filters would work for me in
>> a K3. I am only interested in general coverage reception of SWBC
>> stations, plus operating CW. I am a little unlclear about what filter
>> would be required for AM (reception only), with the KBPF3 option.
>>
>> For CW I generally prefer a wide filter (my K2 is set at 2.0 kHz most
>> of the time). I suppose I would want a narrower filter as well but
>> can't decide whether 500/400 or 250/200.
>>
>> Does a 2.1 kHz + 200 Hz filter pair seem like a useful combo for CW?
>>
>> Finally, I don't have a clue what noticeable difference there would
>> be between a 200/5-pole and a 250/8-pole. If the difference is really
>> subtle or limited to very occasional use I suppose I'd go for the
>> cheaper one.
>>
>> 73,
>> Drew
>> AF2Z
>>
>>
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