[Elecraft] Recommended filters for Diversity Receive?

[Edward R Cole]

John W2ID:

You do realize that these are roofing filters and that operating bw 
is set by the DSP?  Of course if you are operating in a dense high 
signal environment (lots of QRM on adjacent freq) then having a 
roofing filter that matches your operating bw is helpful.

I have both main and sub Rx but only use a duplicate of my SSB filter 
(2.8-KHz 8-pole) in my sub receiver.  I initially bought a 13-KHz 
filter for the sub-Rx not realizing it was not going to be used for 
diversity on FM so I sold it soon after purchase.  I have 13-KHz 
because I use my K3/10 with VHF/UHF transverters operating FM.  I do 
no AM but can use that filter for AM.  I also bought a 400-Hz filter 
thinking it would help receiving CW, and it does (almost too good). 
But having more noise suppression in the narrower bw does help weak 
CW copy (since I only use CW for eme).

Adding more filters to the sub-Rx is not as difficult as to the 
main-Rx.  The sub-Rx has to be removed to add/remove or change 
filters in the main-Rx.  So try to get the arrangement in the main-Rx 
before installing the sub-Rx.

But for casual CW listening I usually dial DSP bw to 1.0 KHz for 
easier listening.

I only run diversity mode for running 2m eme using digital mode of 
JT65b using MAP65 sw which enables dual receive of two receivers.

But like the KX2,  both K3 and K3s do not provide IQ interface, so I 
tap off the 1st IF of both receivers to go to two SDR which are 
phase-locked in frequency so that diversity info is preserved at the 
soundcard.  Because I tap off the 8.2 MHz IF's the signal does not go 
thru the roofing filters or the DSP in the K3.  The K3 merely acts as 
a tunable down converter from 28-MHz which what my transverters input at.

I know this has little to offer in your decision on filters to 
install.  I kept it simple (one SSB filter in my  sub-Rx).


73, Ed - KL7UW
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