In a message dated 11/1/04 8:36:41 PM Eastern Standard Time, [EMAIL PROTECTED] writes:
> I cannot help but note that the venerable Kenwood TS-930S and TS-940S > rigs had their big hunk of a power transformer mounted right next to the > PLL section - and no hum problems were apparent, and it was NOT a > toroidal type transformer, just a standard E+I section type, with no > outer cover - you could see the laminations and windings. > > > Yes, the PLL assemblies were inside shielded compartments, but there did > not appear to be anything special about them - specifically, they were > not "Mu Metal", although they were steel. There's the answer. Steel is ferromagnetic, aluminum isn't. Steel isn't as good a shield as MuMetal, but it does the job. I suspect that a K2 built with a steel cabinet would be much more magnetic-field immune than the stock aluminum case. It would also weigh a lot more, but that may not be a problem for home use. However, the radio would > > operate just fine when the shield covers were open - as during testing > and alignment, so the shielding or lack thereof (in the Kenwoods) was > not germane to that sort of problem. Was the entire shield removed, or just the covers? I suspect a lot of the shield wss still in place. What was different about their > > design that made it "hum proof" - at least from fields induced by the > mains transformer? > > The steel shield is a big factor. Another is that they may not have used iron-core coils in the PLL, or used a different type of iron. Yet another is the frequency range of the PLL. The prime suspect, IMHO, in the K2 hum pickup is the PLL coils with their iron cores. 73 de Jim, N2EY _______________________________________________ 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
