[Elecraft] K3 Received Signal Drops When Roofing Filter Switched In

[engineercm]

Gents,

I wasn't sure how to even search for a question similar to mine, so if this
a duplicate, please forgive me.
Have a K3 with the 400 Hz 8-pole filter.  With the band conditions being so
poor, I've been experimenting with different settings of DSP on weak
signals.  I've also been experimenting with NR on weak signals.  

Tonight I as listening to D4D on 17m CW.  Using NR with a wide setting for
DSP, I could copy him fine. When I turned OFF the NR and readjusted DSP to
400 Hz (where the filter kicks in), the noise level dramatically dropped as
did the signal.  In fact, I could copy him better at 450 Hz when the roofing
filter is not switched in.  It's almost like there is some insertion loss in
the filter.  Is that what I'm hearing?  I would expect a step-function
change in noise between 450 hz (no roofing filter) and 400 hz (roofing
filter) but not the signal.   

I'm using headphones and the Rx Eq is set up to per p.127 of KE7X manual
with 6db boost at 400 hz and 800 Hz.  

73,

Clark/WU4B



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