> I think Doug has hit the nail on the head. For casual CW, > just use the DSP. If it isn't good enough, you can always > add the 500 Hz roofing filter later.
The take-away advice was to not add any additional filters until: 1. You know what bandwidth(s) you will use a lot in each mode of interest, AND 2. You know that you have large signals near your operating frequency that interfere with the DSP filtering. Most of us seldom have condition 2, so the DSP filtering is completely satisfactory with the 2.7 or 2.8 kHz roofing filter. Unless one is very sure about both points above, it makes much more sense to use the K3 for a while until you have definitive answers before selecting protective roofing filters. > For more serious CW operating, I'm thinking the next filter > to get is the 1 KHz filter to give better > tuning-across-the-band performance. My 3rd choice would then > be the ultra narrow (250?) filter. As has been stated many times on this reflector, the 250 Hz 8-pole filter is actually 370 Hz at the -6 dB points. Review the filter plots on the Elecraft web site. If you already have a 400 (actually 435 Hz) or a 500 (about 520 Hz, I think), then the "250 Hz filter" is superfluous. If you need a narrow roofing filter for crowded 160 meter band conditions, then the 200 Hz 5-pole is an excellent complement to the 400 or 500 Hz roofer. The only cases I see for the 250 Hz filter are: A. If you do NOT have a 400 or 500 Hz filter and want a slightly tighter CW/RTTY filter, then 370 Hz (called "250 Hz") is great. B. If you are primarily interested in RTTY contesting with very crowded band conditions, then the 370 is the tightest roofing filter now available for the K3 that doesn't roll off the outside passband of a 170 Hz shift tone-pair. Even so, I often use 200 Hz DSP and tolerate the roll off in exchange for attenuation of more of the pile-up. When the variable crystal filters come out, the 200-500 Hz (or whatever it turns out to be in that range) will be another excellent alternative. 73, Ed - W0YK _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
