[Elecraft] K3: use of 1.8 filter - clarification

[DOUGLAS ZWIEBEL]

IMHO, there are few folks in the contest world that are better
technically than Bill (W4ZV), so I would suggest that everyone take
his comments very seriously.

Bill...I do have a question or two, with respect to your statement below.

1.  Just how often do you find that you run into a situation such as
you describe below?  I don't mean simply, "during every a contest," I
mean more like how often during a contest?  For how many Q's?

2.  If the really close and really strong signal is pumping your AGC,
why not just turn off the AGC and ride the RF?  This is not a
rhetorical question, because I know you do this.  So I'd like to learn
why you would, in some situations, prefer to not do that.  I would
love to learn a new trick!

3.  And just out of curiosity (on SSB), how long would you tolerate
being so close to someone who would pump your AGC?  Of course, for me
(QRP), the answer is zero seconds.  :-)

W4ZV said:
I agree IMD reduction is not a big issue on SSB but blocking dynamic
range (BDR) is the primary reason I sometimes need a narrower filter.
If you have an S9+25 SSB signal CQing next to you (sometimes the case
in  crowded contests), a narrower filter will prevent it from
de-sensing your receiver.  If part of the interfering signal falls
inside your 2.7k filter, signals on your frequency will be gain
modulated by his signal (commonly called   AGC pumping).  In this case
a narrower filter will prevent the problem.  Of course when this
happens, we still have to contend with his transmitted "splatter"
(typical SSB TXs run -35 dB IMD which would result in ~S7 splatter
from an S9+25 signal), but at least you can still copy signals at S7
or above (and lower when he's not transmitting).

73,  Bill