Interesting to note that the 250 hz 8 pole filter actually has a -6 dB bw of 370 kHz.
-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Bill Tippett Sent: Thursday, May 03, 2007 9:13 AM To: [email protected] Subject: [Elecraft] 8-pole vs. 5-pole roofing filters? roofing filters? Good question, but the answer is more than simply bandwidth and shape factor. You need to know its performance *in the radio^ with IMD and BDR measurements. As ARRL discovered with Orion's 500 Hz 8-pole filter, it had much worse IMD than the stock 1000 Hz 4-pole. Granted this had much to do with a poor circuit design but there is no substitute for *in radio* measurements, since the gain distribution for a 5-pole versus 8-pole MUST be different due to different insertion loss which can affect overall IMD/BDR performance. >For crowded-band CW performance am I better off with a 5-pole 200-Hz or a 8-pole 250-Hz filter? Given no IMD/BDR issues, probably the 250 because of better skirt selectivity, but you really should look at the individual filter response plots to know for sure. >Also, do I need separate roofing filters for the main and sub-RX? Yes, 5 slots available in both. 73, Bill W4ZV _______________________________________________ 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 _______________________________________________ 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
