[Elecraft] Filter loss

[Tom Hammond]

Hi Stewart:

At 06:07 PM 6/20/03, Stewart Baker wrote:
>I will try to send the message again this time with another mail program
>
>K2 S/N 3527.
>
>On SSB if I switch to FL2 (2.0khz) I get a loss of about 6dB compared to 
>FL1 OP1, the same loss occurs with FL3 & FL4.
>
>Is this normal ?
>
>I have done the 2.5khz filter mod which works well.

What you are seeing is generally normal.

ANY time you receive SSB through a filter other than the OP1 filer 
(regardless of which FLx has been chosen), you are receiving through the CW 
filter which was not designed for use in the SSB mode... though it _can_ be 
used in SSB receive, but with some level of signal degradation due to 
excessive ripple within the CW filter passband. this is most readily 
evident if you use the Spectrogram program and your PCs sound card to 
actually WATCH what the CW filter passband looks like as you narrow/widen it.

This does NOT mean that the CW filters are not usable on SSB... heck, I use 
them all the time when I'm operating SSB (about 0.5% of my HF operation), 
but I _do_ use them when I'm SSB contesting. The added signal loss, unless 
on very weak signals, is generally not a significant problem, and you CAN 
use them to narrow down the passband in some instances to where the 
received signal is much more easily copied, even though it may be a bit 
weaker due to passband ripple.

Hope this helps.

73,

Tom Hammond   N0SS