On 3/30/2011 11:10 PM, Fred Atchley wrote: > My P3 started displaying persistent clumps of noise across each band. These > clumps reoccurred at about every 72KH over most bands.
This is the signature of a switching power supply. They are everywhere, and most of them are noise RF noise generators. Spectrum displays like the P3 are very useful in exposing noise sources like these. You find and eliminate one and you start seeing weaker ones. The noise comes and goes and you and your neighbors turn on and off the equipment powered by these nasty little buggers. You'll also see them drift up or down in frequency as they warm up, and drift up and down as their oscillator frequency is dithered (frequency-modulated by noise). RFI regulations limit the field strength at a single frequency. Dithering is a cheat that makes it easier to stay below those limits by spreading the noise over the dithered bandwidth. I recently identified the source of really loud noise on 12M as coming from the switching power supply for my SteppIR controller. 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
