A few days ago somebody was asking who it might be who's been experimenting with shielding on the KSB2 board. I was that guy I suspect, because nobody else I've observed on this net seems to be as annoyed as I about the bad skirts, high ripple, bad ultimate selectivity, etc. when the K2 is used with the KSB2. This is an unbelievably competent radio; no matter whether it's measured against $10,000 machines, $600.00 machines, or whatever. BUT------------------------ The performance of its filter, and the way that it performs when installed in the radio, is DISMAL!!!!!!!! On sideband, tight skirts (the electronic kind, gentlemen!) are terribly important, maybe more so than on CW. There is nothing neater than listening to a weak SSB signal through an IF system that has a 1.2:1 shape factor. That complete absence of interference on the sides is marvelous to hear. I'd be surprised if the KSB2 manages 2:1. Just tune through loud broadcast signals on forty meters sometime; listen to the audio "images" the other side of zero beat even on moderately strong signals. If this radio were a piece of junk that might be acceptable. On a radio that is truly world class in every other respect it's absolutely unacceptable. Take a look at something like a TR-4C; the way the sideband switch is oriented so that the input side of the filters cannot "see" the output is typical of the care that used to be taken with filter installation. Similar with Collins S line receivers: those not so wonderful mechanical filters are, nevertheless mounted in such a way as to utilize every drop of filtering that's available. That was fifty or so years ago! How far have we come? I have had good success on the KSB2 with shielding the input and output toroids in little tine cans. Yeah, I know, toroids are self shielding; but even the small wires that go into the board act as little antennas. I've also tried putting a small shield on the bottom of the board, separating the input from the output. It works, as well. All of these things work, but I'm more than a little disappointed that apparently no concern was given to filter isolation when the design was originally created. How about somebody designing a filter? I've contacted Inrad; they already have a CW filter for the K2, but the K2's CW performance isn't as much of a problem as it's sideband performance. Inrad doesn't just doesn't seem to be interested in coming up with a sideband filter. Is anybody else as annoyed as I am about this stuff?
Merlin W3ICT _______________________________________________ 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
