Hi Jim, Yeah, I thought about adding additional electronics (I could get a PIC in there that way!) but I just did this as a quick experiment to get some experience with low-power radar. I'm sure that there are various harmonics in the signal from the lamp, just as you say. If I get a chance, I'll load a section of the WAV file (containing the buzz) into MATLAB and do an FFT to see what freq components I see. It would also be interesting to see the spectrum of the echo from the fan! Here is the info on the gunnplexer, copied from an earlier email: http://shfmicro.com/gunn.htm (go half way down the page to the 10GHz one) I see that they have now gone up to US $86, though, I think they were about $70 when I bought one. Good luck! Sean At 09:01 AM 3/14/09 -0600, you wrote: >It would seem to me that you could add a frequency counter, and calibrate >frequency to speed. > >About the flourescent light deal, my guess is that the lamp is such a non >linear device that the 60 Hz being fed into it is being distorted to the >extent of creating many higher order harmonics, and the radar gun is >concentrating these high order harmonics and that's what you're detecting. > >BTW, how much was the Gunnplexer? I am a Ham and would like to get one for >some experiments I have in mind. > > Regards, > > Jim > > >-Original Message----- >From: Sean H. Breheny >To: PICLIST@MITVMA.MIT.EDU >Date: Friday, February 22, 2002 11:54 PM >Subject: [EE]: 10GHz and fluorescent light > > > >Hi all, > > > >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 and hear a > >tone which varies with their speed. I also can get some very interesting > >sounds by pointing it at my PC's power supply fan or the CD drive while it > >plays a CD or is ejecting a CD. I recorded a WAV file of this and I put it > >up on my web site: > > > >http://www.rocket-roar.com/BT > >(look under the section on "Small Doppler Radar Experiment" about 1/4 down > >the page) > > > >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). > > > >If it were simply a case of the audio amp picking up 60Hz noise, I wouldn't > >think that the antenna direction would make a difference, only the > >proximity to the lamp. But it makes a profound difference whether I point > >the horn antenna at the lamp or not. 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? > > > >Sean > > > >---------------------------------------------------- > >Sign Up for NetZero Platinum Today > >Only $9.95 per month! > >http://my.netzero.net/s/signup?r=platinum&refcd=PT97 > > > >-- > >http://www.piclist.com hint: The PICList is archived three different > >ways. See http://www.piclist.com/#archives for details. > > > > > >-- >http://www.piclist.com hint: The PICList is archived three different >ways. See http://www.piclist.com/#archives for details. ---------------------------------------------------- Sign Up for NetZero Platinum Today Only $9.95 per month! http://my.netzero.net/s/signup?r=platinum&refcd=PT97 -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.