Ken, > I am looking for something somewhere that will help > me decide between the two.
I went back and forth several times before I finally decided to go with the 8-pole filters. 1) The 2.8 Khz filter is actually a bit tighter than the 2.7 Khz filter. As W4ZV writes: > 1. 6 dB bandwidth and 6/60 dB shape factor: > > Filter BW(-6dB) Shape Factor > > 2700 2910* 2.9 > 2800 2888 1.6 > > *The 2.7k may have wider BW than the 2.8k. This is > Elecraft's measurement and my 2.7k closely agrees with it. 2) If you extend the analysis to the skirts, the 2.8 KHz filter shows some significant bandwidth advantage at -30 dB. Using a simple linear skirt approach I first used for comparing the CW filters we see: > 2700 2800 > ------------------------------------------------- > - 6dB 2910 2888 Hz > -60dB 8329 4620 Hz > slope 50.18 16.03 Hz/dB > > -10dB 3311 3016 Hz > -20dB 4315 3337 Hz > -30dB 5319 3657 Hz > -40dB 6322 3978 Hz > -50dB 7326 4299 Hz While the shape/width of the roofing filter is not critical, the added selectivity can't help but be some benefit when the strong station fires up 2.5 KHz away. 3) Eric indicates that the 8-pole filters are tested to a higher standard than the 5-pole filters. They will have less filter IMD than the 5-pole filters. For me, the little things added up. I decided "better safe than sorry" was the best course of action ... I ordered the 8 pole filter up front rather than possibly regret not doing so every time I used the radio. However, the second receiver will have the 2.7 KHz filter. 73, ... Joe, W4TV _______________________________________________ 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
