Hi all, I'm trying to make sure that I understand something kind of weird that I ran across today; I hate resolving a problem without fully appreciating everything that was causing it.
Since 10M was pretty active today, I thought I'd pop on, and since the ground was nice and wet, I thought I'd give my "Home Depot" ground-mounted vertical a go. (It's a vertical made entirely out of things you'd find in Home Depot's plumbing, lumber, and window departments. I didn't have the tape-measure radials connected today, just the ground stakes around it.) Midway through the day I started picking up what looked and sounded like a 60Hz + harmonics buzz. I did not have a power supply connected to the KX3, and I pulled all the other connectors from the computer to make sure I wasn't getting some kind of ground loop hum. No dice. To make matters more interesting if I backed the antenna connector halfway off, such that the ground was no longer connected, the hum disappeared. I started worrying that I was having some trouble with the local utility, but decided I'd better rule out something in the house first. Through the course of troubleshooting, I came to find the culprit was a USB phone charger on the other side of the wall from the antenna, with the USB cable stretched out across the floor. Unplugging it or disconnecting the USB cable mostly made the noise go away (but not entirely, though there are so many different power supplies and things inside the house, there could be multiple sources of noise, too). I mostly sorted the problem by winding the proximal end of the USB cable about 6 times through a ferrite core, though a small amount of noise remained just by virtue of the thing being plugged in at all. Then I noticed that tuning up or down a few Hz had no effect at all on where the noise showed up in the waterfall, which got me wondering if it was a noise getting picked up in decoding. I set the RX SHFT setting to 8.0, and indeed, the noise disappeared entirely. I don't completely understand the "why" part of what happened here... that is to say, why did it change based on whether the ground side of the antenna was connected or not, and why did changing the RX SHFT get rid of it? (Also I note that the ground is particularly wet and conductive today, which may or may not be a factor in why I noticed it today.) Any thoughts? Nick -- *N6OL* Saying something doesn't make it true. Belief in something doesn't make it real. And if you have to lie to support a position, that position is not worth supporting. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
