Tell him he should buy a K-3.
---- Dick Green WC1M <[EMAIL PROTECTED]> wrote: > Hi, > > > > I'm looking for articles on how the new roofing filter designs work. I've > seen the PowerPoint on Rob Sherwood's site, but it doesn't answer all my > questions. > > > > Questions came up in a discussion with a friend of mine who is considering > the INRAD roofing filter mod for his Kenwood TS-950SDX. He operates almost > 100% CW, and doesn't hear any IMD products. His beef is noise from stations > that are just outside the passband of his cascaded IF crystal filters. He's > hoping the roofing filter will increase the selectivity of the radio. > > > > My sense is that it will help, but not by providing additional selectivity. > My understanding is that it will improve the dynamic range within the > passband by keeping the hardware AGC in the downstream IF stages from being > triggered by loud adjacent signals. Is this the correct way to think about > it? > > > > My friend maintains that the roofing filter would provide selectivity as > well, but my sense is that unless it's narrower and/or has steeper skirts > than the IF filters, it won't. I believe the Kenwood roofing filter mod is > only on the order of 2K-3K wide, so the selectivity shouldn't improve. > > > > Even if the roofing filter was the same or narrower than his IF filters, > would it improve selectivity? Is there an analogy with cascaded IF crystals? > Typically, a filter in the final IF stage (e.g., in the 450KHz range) > outperforms a filter in an earlier stage (e.g in the 8 MHz range.) Is this > because it's easier to make better filters at lower frequencies, or because > it's more effective to filter after any amplification by previous IF stages? > > > > Obviously, I don't know squat about this. > > > > 73, Dick WC1M > > > > _______________________________________________ > 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
