I got one for you that goes to show everything does have a fundamental resonant frequency.
I had recently purchased an Icom AH-4 antenna coupler and was trying out antenna configurations. I had never used a tuner or coupler before, but I "thought" I knew what I was doing (NOT!). I decided to mount the AH-4 under an eve on the end of the house and run a long wire out to one of the trees in the back yard. So far, so good. Since the antenna coupler was about 16 feet off the ground and it needed a connection to ground, I ran a 1" ground strap to the earth and terminated it with a ground rod, since that is what the instructions "told" me to do. Being extra smart, I tied this ground rod to the A/C service ground as per the NEC. Now, remember that 16' long ground strap? Ok, now what is the length of a wire that is 1/4 wavelength on 20 meters? About 16'. So, I crank this puppy up with 100 watts and I am now effectively transmitting a 20 meter signal into the ground of my house wiring. The one device that REALLY didn't like this was my powered subwoofer for the Home Theater that started feeding back at the EXACT resonant audio frequency of the metal chimney connected to the fireplace insert. It REALLY starts oscillating since I have magically "found" its fundamental resonant frequency. It made the loudest noise; sounding like the walls were being drummed on by some giant Org. The dogs went crazy. The XYL is running through the house screaming, thinking that a tornado is hitting the house. Now I'm at the other end of the house, the shack door closed, headphones on making QSOs as fast as I can with Europe using my new antenna. I can't hear a thing going on in the far end of the house. The shack door bursts open, which does get my attention and in flies 2 dogs and a XYL totally freaking out! Needless to say it was easy to find the root of the problem and I decided that I needed a little more fundamental knowledge about what a "real" RF ground is and why balanced antennas a really good things. The fireplace was grateful too. -Tim --- Integrated Technical Services "Too much of everything is just enough." -Rob Barlow -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Mike Naruta Sent: Monday, September 11, 2006 7:53 PM To: Allen Boehm; FlexRadio@flex-radio.biz Subject: Re: [Flexradio] SDR1000 WPI (Water Pipe Interference) Problem Yep, it was an interesting demonstration on Mythbusters. Too bad Jerry changed it. I'm guessing that it would not have vibrated with just carrier. Mike - AA8K Allen Boehm wrote: > It is not an urban legend. Every thing has a resonate frequency. If > you dig back into the history of Nikolai Tesla and his earthquake > machine. Here are two related patents registered by Tesla: Patent No. > 511,916 (Jan. 2, 1894) titled "Electric Generator" and Patent No. > 514,169 (Feb. 6, 1894) titled "Reciprocating Engine". > Al > _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
