[Elecraft] CW Filter and Roofing Filter

[Don Wilhelm]

Robert,

Actually there is no good comparison with either your Yaesu or the TenTec.
The DSP sets the ultimate signal bandwidth and is continuously variable 
from greater than 2.8kHz down to 50 Hz.  There is no specific CW 
filter.  Adjust for a width that is appropriate for your mode, band 
conditions and your personal choice of a good filter width.

That leaves the question of the roofing filter(s) unanswered.  The K3 
(or K3S) will work with only the stock 2.7kHz or the 8 pole 2.8kHz 
filter - you must have one or the other in the K3.
Other roofing filters may be desirable in your K3 when you are working 
in crowded band conditions where there may be strong nearby signals that 
are outside your DSP filter, yet are within the passband of the roofing 
filter - in other words, you may not hear them.  Those strong signals 
will activate the hardware AGC (which is there mainly to protect the A 
to D converter from overload).  If those signals activate the Hdwr AGC, 
you will hear "AGC Pumping" in the receiver and the receiver sensitivity 
will be reduced when that strong signal transmits.
The cure for the effects above is to add narrow roofing filters to 
reduce the K3 response to those nearby strong signals.  The roofing 
filters are automatically switched in as you narrow the DSP filter 
bandwidth.

73,
Don W3FPR

On 6/23/2015 2:42 PM, rclark01 at comcast.net wrote:
> Hi all:
> I currently own a Yaesu FT-950 and am considering selling it to move the the Elecraft K3S line. My question is about filters. My FT-950 has a roofing filter and a variable CW filter down to 200hz. Quite frankly, I can't tell much different when I switch in the roofing filter but the variable CW filter makes a big difference. I also have a 1970's TenTen Century 21 which has a 500Hz filter that, to me, seems to do a better job than the FT-950. So..when I read that a 500 Hz roofing filter is an option for the Elecraft K3S, what am I actually reading? Could there be a 500Hz roofing filter and a 500Hz CW filter or are they the same? In several Youtube videos, I've seen operators using the variable width the filter signals. What am I seeing? Are they adjusting the roofing filter or the cw filter? And...is the cw filter variable (like my FT-950) or fixed (like the Century 21)?
>