[Elecraft] K3 TX CW Filter selection

[Joe Subich, W4TV]

On 2025-12-06 2:34 PM, Rick NK7I via Elecraft wrote:
>   2.7 can be used in all modes but FM (not wide enough).

2.7 can not be used in AM (not wide enough)

AM requires either the 6 or 13 KHz.  FM requires the 13 KHz.

Factory default is to use 2.7 or 2.8 KHz for SSB, data and CW
transmit.  Bandwidth is defined by the DSP modulator - the only
need for the IF filters in transmit is to remove the mixer image
at 8245 KHz.

73,

    ... Joe, W4TV


On 2025-12-06 2:34 PM, Rick NK7I via Elecraft wrote:
>   2.7 can be used in all modes but FM (not wide enough).  As you narrow the bandwidth control, the filters will switch (if in place and enabled).  (Also from memory, now using K4s).
> 
> To answer the OP, I suppose someone might want to hear a 2.7 KHz wide CW spectrum but that’s a lot of abuse to the ears; 500 (even in a contest) would make more sense.  If other narrower filters were installed, I wouldn’t use 2.7 on CW.
> 
> (250, is really about 325, it’s not that sharp.  Most found it not worth the expense.)
> 
> 73,
> Rick nk7i
> 
>> On Dec 6, 2025, at 11:21 AM, Rich Newbould via Elecraft <elecraft at mailman.qth.net> wrote:
>>
>> If memory serves my correctly the 2.7 filter is used for TX on all modes, except AM
>>
>> I could be wrong
>>
>> Rich
>>
>>
>>> On 12/6/2025 1:35 PM, Tony Casciato via Elecraft wrote:
>>> Was poking around in the K3 Utility this morning and noticed in the
>>> Configuration tab/Crystal Filter Configuration panel there are Radio Button
>>> choices for a TX CW filter to use Filters 1 thru 5; mine defaults to Filter
>>> 3 which is the 2.7Khz 5-pole standard one. I also have Filter 4 (500Hz
>>> 5-pole) and Filter 5 (250Hz 8-pole) available. Should it be set to
>>> something different for CW?
>>>
>>> I looked in the "Help" text, asked Google and didn't see an option to
>>> search these Mailman messages. I figured it was ok to ask here once and
>>> it's mostly a curiosity.
>>>
>>> Thanks and 73,
>>> Tony, KX3H
>>>