Re: K3 Filter advice...

Posted by John W2XS on Dec 26, 2007; 4:10pm
URL: http://elecraft.85.s1.nabble.com/K3-Filter-advice-tp457507p457508.html


There were many great posts about the filter options.  Thanks to all who provided good advice. I read all of them. This is my take on all of the postings about filters.

1. The shape factor of a roofing filter is not as important as the shape factor of a conventional main IF filter.  Therefore, a 5-pole will be fine for a roofing filter.  Based on this, I went with the default 5-pole 2.7kHz filter. Since I am a CW operator, I also went with the 500 Hz and 200 Hz CW filters.  The 200 Hz may be overkill since the rig has the "shift" control, but it was not that much more money.

2. The widest roofing filter determines the widest receiver selectivity.  In other words, you must have a roofing filter installed - you cannot "jumper" over a slot for wide hi-fi selectivity. Based on that, since I also like to listen to SW and AM BCB, I added the 6 kHz AM filter.

So my widest bandwidth will be 6 kHz and the narrowest bandwidth will be whatever the DSP can do (50 Hz or so) in series with a 200 Hz roofing filter.

That sounded like a good combination to me.  The biggest problem will come when trying to listen to a weak station who is near another station with a "noisy" transmitted signal.  

Time will tell if my assumptions are valid, but I was happy with the choices when I ordered.

73,

John W2XS

KX1 (S/N 015 and S/N 925) w/KXPD1, KXAT1, KXB30
K2 (S/N 1116) w/KAT2, KSB2, K160RX, KIO2, KBT2, KNB2, KAF2, FDIMP
K3/100 (S/N TBD) w/KAT3, KBPF3, KUSB, KFL3A-200, 500, 2.7K, 6K
HexKey (S/N 113 )
DL1, BL1, BL2, N-gen, XG1, BNC-MM