Ken K0PP has pointed out I said it all wrong. With my poor choice of the terms I have confused even myself, and produced gibberish. I'll quote Ken because he said it clearly:
Loops, if built correctly, have a NULL in both broadside directions ... through the hole in the loop, so-to-speak. The nulls are -very- narrow, but deep and are essentially the only directivity exhibited by a loop. I've successfully used the cardboard/test-lead loop antenna and TH-F6A HT I described to locate noise coming from a switching power supply for a lamp in a neighbors house, the charger on my robot vacuum cleaner (a menace surely no 1950's ham ever faced), a laptop power supply, and a home music player power supply. Turning off the house breakers is a great first step to tell you what room it's in, but if you already know it's coming from the shack, the small loop helps a lot. Leigh/WA5ZNU > Mitch, > You may be doing this already, but you can make a small loop antenna > for your HT (TH-F6A?) to DF the noise. > A really simple one is just a short SMA to BNC jumper with a square > wire loop (alligator test leads?) taped to a piece of cardboard. > When the loop is broadside to the noise, it will be the loudest, and > when parallel, the null will be sharpest. > This type of antenna is inefficient, and so it work well to DF noise > sources to a few inches. > So you can tell where noise is being radiated inside your shack. (It > might be created in one spot and radiated elsewhere, of course.) > > If you need a better DF antenna for RFI, make a better version that is > shielded, by using a piece of scrap coax: > http://lists.contesting.com/_rfi/2005-01/msg00078.html > > Leigh/WA5ZNU >> Hello, >> I have been hearing an annoying noise on 160m that has a pulse rate >> of about 1/3 of a second. After observing the behavior when I do >> certain things with my K3 and my computer I found that the source of >> the pulsing is Ham Radio Deluxe polling the K3 for VFO changes -- it >> polls every 300ms. However, when HRD is shut down (no other serial >> port activity) the noise is still present as a constant tone with no >> pulsing effect. My first suspicion is the USB to Serial adapters on >> the computer, but I am also thinking that maybe the noise is coming >> from the USB hubs or their wall warts. I can hear the noise on the >> K3, my winradio, and my handheld (which is picking up the noise on >> 80m). I was wondering if anyone has seen something like this and >> whether this might be coming from inside the computer or the USB >> hubs. I am going to pull out my desk from the wall and start >> tracking this down to the source but I wanted to see if anyone else >> had experience with this sort of thing and any thoughts or >> recommendations? >> >> Best Regards, >> >> Mitch Mitchell >> AE5HO >> [email protected] >> >> > > > ______________________________________________________________ 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
