Jan Erik Holm wrote: > > Interesting review. > > Considering IMDDR3 it seems like one should stay > way from the 500 Hz filter, looks like the 400 Hz > is the filter to get. >
I haven't read the review but he must have had a bad 500 Hz filter from what I've heard reported (i.e. the 2.7k better than the 500 Hz). That makes no sense and is contradictory to previous measurements by both Elecraft and Sherwood: Elecraft: Filter 20kHz 10kHz 5kHz 2kHz 200 Hz, 5 pole 100+ 100+ 100+ 95 250 Hz, 8 pole 100+ 100+ 100+ 95 400 Hz, 8 pole 100+ 100+ 100+ 95 500 Hz, 5 pole 100+ 100+ 100+ 94 1 kHz, 8 pole 100+ 100+ 100 94 2.7 kHz, 5 pole 100+ 98 92 n/a 2.8 kHz, 8 pole 100+ 100 93 n/a http://www.zerobeat.net/mediawiki/index.php/K3_Roofing_Filters Sherwood: Filter - IMD @ 2 kHz 500 Hz - 95 dB 400 Hz - 96 dB 200 Hz - 101 dB* *I listed the 200 Hz because it's a 5-pole filter (just like the 500 Hz) in case some believe there is an inherent problem with 5-pole filters. http://www.sherweng.com/table.html It's odd but Peter Hart reported something similar when he did Orion's review. The 2.4k filter was much better than the 1.0k, which again makes no sense unless the 1.0k was defective. I'm sure Peter reported what he measured but common sense would dictate that one should suspect something was wrong with the filter and request another when anomalous results like this are measured. It also reminds me when ARRL once reported better IMD performance with Preamp ON versus Preamp OFF. Common sense would say "TILT"! 73, Bill W4ZV -- View this message in context: http://www.nabble.com/RSGB-RadCom-K3-review-posted-on-RSGB-Members-web-page-tp17869976p17958106.html Sent from the Elecraft mailing list archive at Nabble.com. _______________________________________________ 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
