On Wed, 2007-12-05 at 20:15, Bob wrote: > I am looking for a consensus as to the value of switching the stock > 2.7Khz for the 2.8Khz filter at time of order and paying the > difference based on a $30 credit? I would like some input as to what > the difference really is and what it would mean in terms of > functionality. Additionally, if the 2.8 is that much better, why > would it not be part of the basic radio offering visa vis the 2.7? > > Thanks > > Bob
I suspect you would be hard-pressed to see any difference at all between the 5-pole 2.7 kHz filter and 8-pole 2.8 kHz filter in on-the-air operation. According to the K3 FAQ, only the first 30 dB or so of stop-band rejection is important in the roofing filter - the DSP takes care of the rest. Of course, the 5-pole filter is actually slightly narrower at the -6 dB attenuation point. Let's say the 8-pole filter is narrower at attenuations beyond 10 dB. So the only practical advantage it would have is a few dB better attenuation between the -10 and -30 dB points. If there were a VERY strong signal in that range (say from +/- 1.5 to 2.0 kHz from center frequency) the 8-pole filter might prevent it overloading the ADC/DSP system where the 5-pole might not. To make the more-expensive filter worthwhile, the signal strength would have to be right in that few-dB range where the 8-pole filter would work and the 5-pole would not. I think that's a rare enough occurance not to be worth worrying about. Al N1AL _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
