[Elecraft] Filter Selection Approach

[Don Wilhelm]

Ed,

The DSP filtering is quite effective all by itself - I have only the 2.7 
kHz filter installed and fine it quite effective *except* for heavy 
QRM/pileup situations - like contesting or serious DXing, and when the 
'going gets tough', I go do something other than hamming.

Caution - I am going to present my own opinions here - YMMV.

If I were ordering a bunch of filters, I would have the 13 kHz in the 
main for FM transmit (and receive), and the 6 kHz also in the main for 
AM transmit.  I do not see much sense in having both the 13 and the 6 
kHz in the sub since either can be used for AM receive.  Besides, why 
would you want FM and AM receive only capability (by putting them in the 
sub) if you have no transmit capability in those modes.

If you do SSB contesting or serious DXing, the 2.1 or even the 1.8 
filters may be beneficial, and I would select one width of those two and 
put one of those in the sub and one in the main to allow diversity 
reception (if and when you get a separate receive antenna) for SSB 
operation.

Similarly, I would pair up the narrow CW filters for CW use, and I would 
choose the 400 and the 200 Hz filters.  At 1 kHz CW width, I would use 
the 2.1 (or 1.8) filter and narrow it down with the DSP.  I just cannot 
foresee conditions where I would want to listen to a wide CW bandpass 
under conditions when the DSP could not handle the dynamic range.  My 
normal CW tuning is done with a 500 to 700 Hz bandwidth, so I would 
likely choose a 500 Hz filter for normal CW work and if I were 
interested in CW contesting, I would likely choose the 200 Hz width.

So, my 'ideal' filter setup would be.
Main (with no AM or ESSB transmit capability) - 13kHz - 2.8 kHz, 2.1 (or 
1.8) kHz, 500 Hz and 200 Hz.
OR -  Main (with no FM transmit or receive capability) - 6 kHz - 2.8kHz, 
2.1 (or 1.8) kHz, 500 Hz and 200 Hz.
Sub - 2.8kHz, 2.1 (or 1.8) kHz, 500 Hz and 200 Hz.

If I wanted both FM and AM/ESSB transmit/receive capability, I would 
bump out the 500 Hz filters and install both the 13kHz and the 6 kHz in 
the main, and the choice of 2.1 or 1.8 kHz would tend toward the 1.8 
because I would use that roofing filter along with the DSP for normal CW 
operation and switch in the 200 Hz filter when the 'going gets tough'.

So my choice for all possible modes would be:
Main -- 13 kHz, 6 kHz, 2.8 kHz, 1.8 kHz and 200 Hz.
Sub ---  2.8 kHz, 1.8 kHz, 200 Hz.

That combination would allow future diversity reception for all modes 
except FM and AM/ESSB where I do not believe diversity would offer me 
much advantage (I would not regularly use those modes), but preserve the 
possibility for diversity reception in SSB, DATA and CW modes.

As you can see, the choice will depend on your operating aspirations.  
Consider the reasons for *my* choices, and then match *your* filter 
selections to your anticipated operation requirements.

I might emphasize that at present, my K3 does not have the subRX and has 
only the stock 2.7 kHz filter installed.  I can always add filters later 
when (and if) I find a need for them.

73,
Don W3FPR

Ed G wrote:
> Hello,
>      I am getting ready to order a K3 with subreceiver soon, and have been
> thinking about which filters to order.  From most of what I read, folks seem
> to order duplicates for the subreceiver of what they have ordered for the
> main receiver, or perhaps just go with just a couple narrower ones for the
> subreceiver. Since I work mostly CW, and am not too interested in diversity
> reception (don't have the antennas either), I was thinking of the following:
>
> Main Rx: 2.8 - 1.8 - 1 - 400 - 200
> Sub Rx: 13 - 6 - 2.8 - 2.1 - 1 or 400
>
> I know that's a lot of filters, but other than going broke, are there any
> drawbacks to this? Has anyone else tried to essentially give themselves all
> the filter options by populating both receivers with different filters?
>
> --Ed--
>   
>