[Elecraft] K3 Filter question - SSB

[Bill W4ZV]

Barry N1EU wrote:
> 
> 
> Bill W4ZV wrote:
>> 
>> 1. It *WILL* keep your AGC from pumping if there's another strong station
>> within the 1.8 kHz passband. However, do you really think you could copy
>> a weak
>> signal while a S9+30 interfering signal is inside your 1.8k bandwidth? I
>> don't
>> think so. With any typical SSB filter bandwidth, AGC pumping is not a
>> practical
>> issue (it IS a big deal for CW however).
>> 
> 
> Bill, I'm confused by that first sentence.  How can a signal within the
> passband NOT pump the AGC?
> 
> Normally when AGC pumping is discussed, it's a negative reference to an
> adjacent signal that's outside of the passband.
> 
> Barry N1EU
> 

You're correct Barry.  I meant to say just outside your passband.  However,
given that most SSB signals generate 3rd garbage (spurs, phase noise, etc)
in the area of -35 dBc, an S9+30 signal just outside your 1.8k passband will
easily obliterate a weak signal inside the passband.

I found my ears to be the best tool for copying weak signals in the presence
of strong adjacent splatter.  For whatever reason they heard better using
the stock 5-pole 2.7k set to a DSP BW of 2.0-2.1k than the 8-pole 1.8k set
to actuate at DSP = 1.9k.  I tried many times to use the 1.8k but simply
just found the 2.7k worked better for me.  Of course that's just my
experience which wouldn't necessarily apply to everyone.

73,  Bill


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