[Elecraft] [K3] K3NA on 5 pole vs 8 pole filters

[Bill W4ZV]

Alfred Frugoli wrote:
> 
> I remember reading a comparison by I think K3NA on the differences between
> 5
> pole and 8 pole filters that eventually lead me to stick with the 5 pole
> filters. 
> 

Eric and I are both ex-Orion users, which worked well with 4-pole filters so
I concluded 5-poles would be sufficient in the K3.  After receiving my first
K3 I discovered it had a much lower hardware AGC threshold. This led to the
"HAGC mod" which was implemented around S/N 350, but I still don't think the
threshold is as high as Orion's.  Therefore the steeper skirts in the 8-pole
filters are necessary to prevent AGC pumping from close-in strong signals. 
I've since switched from all 5-pole 500s to all 8-pole 500s (Inrads) in both
of my units.  

I suspect the K3 could be improved without other harmful effects by raising
the AGC threshold a little more.  Someday when I have nothing better to do I
may try some experiments to see.  The DSP filters in both rigs are probably
similar but the lower AGC threshold in the K3 makes it more susceptible to
strong adjacent signals if you only use 5-pole filters.  However if you
don't operate in extreme environments like 160 contests you may never notice
any difference.

73,  Bill
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