From: "Sean H. Breheny" Subject: [EE]: 10GHz and fluorescent light > A while back I bought a 10GHz gunnplexer (combination 10GHz low-power > transmitter and simple homodyne receiver) and attached a sensitive audio > amplifier in an attempt to make a simple doppler radar. It was quite > successful; I can point it at cars up to about 100 feet away Mine only worked for 5-10 feet, with a milliwatt gunnplexer and a 'low-noise' audio amp (LF353 is 15nV/Hz^-2 IIRC). Maybe if I had a 100mW diode, an big horn with a lens(rather than a six inch one) and a filter to limit the audio bandwidth to a KHz I could get similar performance? I tried one from an alarm from a ham-fest. You can also find old radar detectors with even weaker outputs, that can be improved by removing those 'idler' screws designed to prevent the local osc from radiating. > For the most part, I understand how this works. However, one thing puzzles > me: when I point it at a fluorescent light, I hear a VERY loud 60Hz hum > (might actually be 120Hz, it is hard to tell because most of what we > usually attribute to 60Hz is really full wave rectified 60Hz which is > actually 120Hz). Probably 120 Hz >So, my only guess is that the radar is > seeing an echo from all the mercury (?) ions being jostled around inside > the light at 60 or 120Hz. I'm not surprised that I would be able to detect > such an echo, only surprised that it is SO strong, it is much stronger, for > example, than the echo from my power supply fan. > > Any ideas? Probably not the Hg ions, but the electrons themselves. Simply, the plasma switches between conductor and non-conductor 120 Hz. It is not merely 60 Hz capacitive or inductively coupled noise, but that could be a component if your circuit is not capacitively and inductively shielded. Plasma is very interesting. It has several types of resonant frequencies, and is affected by the earths magnetic field. I heard cases where spiral wires are wrapped aroundfluorescent tubes, making them into a kind of TWT (microwave traveling wave tube) that can even amplify and reflect radar, jamming it. You know those license plates with the fluorescent tubes wrapped around them? I hear they have a high-frequency ballast, so police radars are jammed by the noise they create. Just what I've read, FWIW. Scott ******************************************************* Is the American Identity freedom to pursue happiness and profit from the fruit of your own labors, or a servant leased to corporations by corrupt federal government taxing you to your tolerance? Colin Powell gives Taliban $43 Million to keep heroin price high for UBL! (Surely a bigger treason than Taliban Walker's!) http://www.robertscheer.com/1_natcolumn/01_columns/052201.htm The drug war counter-offensive: http://www.lp.org/ for our Constitution and Bill of Rights! ******************************************************* -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.