Post by thread:[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.

From: "Sean H. Breheny" <spam_OUTshb7TakeThisOuTCORNELL.EDU> 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!) 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.

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 <.....shb7KILLspam@spam@CORNELL.EDU> To: PICLISTKILLspamMITVMA.MIT.EDU <.....PICLISTKILLspam.....MITVMA.MIT.EDU> Date: Friday, February 22, 2002 11:54 PM Subject: [EE]: 10GHz and fluorescent light {Quote hidden}>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.

Dear Claudio, I used a 10GHz "gunnplexer" made my M/A Com. I think M/A Com has discontinued them and another company has now started to make them. In any event, you can find them here: 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. Gunnplexers are a combination of a Gunn-diode oscillator with a schottky diode mixer. Mine also includes a varactor diode for tuning the radar frequency (but I don't bother to use it, just tie it to a fixed voltage). The Gunn diode (which produces about 10mW in this one) not only produces the output power but also excites the mixer. Any incoming signals are mixed with the carrier in the mixer, and the output is low-pass filtered to the audio range and then amplified by (IIRC, I'd have to take it apart again to check) half of an LMC6482 dual op-amp and then an LM386 to drive the headphones. I also bought a metal-plated plastic horn antenna from the same company (shfmicro, address given above) which is meant to mount right onto the waveguide flange on the output of the gunnplexer. Sean At 11:52 AM 2/23/02 +0100, you wrote: >Small question: what radar sensors and transmitter are inside that box? >We had a small radar experiment also, but the sensor we used was >discontinued... > >{Original Message removed}

Hi Scott, Actually, I'm using the 10Ghz M/A Com gunnplexer from shfmicro (the company that you told me about in a personal email which was a reply to a question on the piclist months ago). Thanks for telling me about them, it's a great company! I did some back of the envelope calculations using the datasheet for the gunnplexer and this suggests that you should be able to get a 1:1 signal to noise ratio in a typical audio bandwidth (a few kHz) with the 10mW source and the small (about 5 inch wide) horn when pointed at an object of 1m^2 radar cross section at 50 feet away. In my circuit, the audio amplifier produces about the same amount of noise as the gunnplexer, and I am barely able to detect with my ear echos from cars as far away as 100 feet. At 50 feet the echo can be easily heard. I think that an audio filter helps, but I am puzzled as to why you didn't get similar performance. About the electrons vs. ions, I wonder what the RCS of an Hg ion is at 10GHz? I have actually seen the figure for a free electron, and it's pretty darn small :-), although if you have trillions of them(or even more!), it does add up! I saw an article from a car magazine where they tested various police radar countermeasures. They said that some of them contained several fluorescent tubes with wire wrapped around them (like you said) and they had no effect. This is probably a case of something that would work if you made it very carefully and energized the tube properly but has little chance of working if you just throw it together in a plastic case. Sean At 07:11 AM 2/23/02 -0600, you wrote: {Quote hidden}>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!) >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. ---------------------------------------------------- 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.

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: {Quote hidden}>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 <EraseMEshb7spam_OUTTakeThisOuTCORNELL.EDU> >To: PICLISTspam_OUTMITVMA.MIT.EDU <@spam@PICLISTKILLspamMITVMA.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! > >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.

Hi Zim, Yes, now that you mention it, I do see how it is a much smaller version of Auroral propagation! Sean At 05:43 PM 2/23/02 +1100, you wrote: {Quote hidden}>Sea, > > > 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? > >Inside the Fluoro' tube is a column or ionised gas which is thrashing around >like an angry snake, >as well as being formed and extinguished at a 100 Hz rate. > >By definition, it is heavily ironised/conductive and thus reflects radio >waves exceedingly well... > >I guess your experiment is similar to the ham radio operators who bounce >signals off the Aurora. >They hear very strong signal which are heavily modulated and distorted by >the rapid movements of the Aurora > > >............................ Zim > >-- >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.

From: "Sean H. Breheny" <KILLspamshb7KILLspamCORNELL.EDU> > Hi Scott, > > gunnplexer from shfmicro... Thanks for telling me about them, it's a great > company! Your welcome. I visited the them several years ago, great people, kewl stuff. >...you should be able to get a 1:1 signal to > noise ratio in a typical audio bandwidth (a few kHz) with the 10mW source > and the small (about 5 inch wide) horn when pointed at an object of 1m^2 > radar cross section at 50 feet away. In my circuit, the audio amplifier > produces about the same amount of noise as the gunnplexer ... > I am puzzled as to why you didn't get similar performance. My noise increased significantly when the gunn diode was energized. I should correct myself and say that the of the several units I've used, the alarms used a short approx. 1"x2"x2" horn, with a wide field for area protection. I could trigger at 10 feet and hear targets up to 20'. The 20 GHz thumb-sized units were very dissapointing. not over 5 feet. The gunnplexor with the 6" horn just didn't work as well. You may have gotten a new unit, I got the cheaper 'junk'. Got my alarms at a hamfest. Perhaps as the gunn diodes age, they get weak and noisy. > About the electrons vs. ions, I wonder what the RCS of an Hg ion is at > 10GHz? I have actually seen the figure for a free electron, and it's pretty > darn small :-), although if you have trillions of them(or even more!), it > does add up! Your talking about bulk behavior. The atomic cross section would be in electron volts for photons. And the nuclear cross section in Barns. Many orders in magnitude between the bulk (tube) scale, atomic and nuclear scale. Whipping out my handly "NRL Plasma Formulary" (Do a web search and download a PDF or they'll even mail you a free one. I wish I could feel so greatfull more often!) Electron plasma (Langmuir) frequency * 2 Pi = (4 Pi Ne E^2 / Mi)^1/2 where Ne is electron 'number' (charge) or particle density, E is charge of electron and Mi is mass electron cyclotron (gyro) resonant frequencies * 2 Pi = E B / Mi C where B is magnetic field Similar frequencies for ions, but with ions you multiply the numerators by Z (charge-ionization state) and divide by ion mass. So typicaly your electron frequencies are in GHz and ion frequencies are in MHz, because ions (especialy heavy metals!) are massive and vibrate slowly, and are in charge equilibrium with the electron (1000x lighter). As you increase a magnetic field the gyro and plasma frequencies begin to separate. The gyro resonance is like a microwave magnetron type resonance. As the plasma gets hotter, the electrons vibrate faster and are more mobile and the 'Debye' length (the insulator/conductor transition distance) shortens. Much above the plasma frequencies the waves wont strongly interact, until you get to molecular resonance and atomic photon absorption spectral lines. Then (much) further up, nuclear resonances and energy level transitions. At the plasma (and gyro) frequencies, you can get negative resistance - plasma maser (not to confuse with molecular maser) action. Very similar to the Gunn effect in semiconductors! And there's Landau damping - absorption. Of course magnetic fields are anisotropic, and make a plasma look 'capacitive' across the field lines because the electrons must curve. And as they curve, there path is longer, the frequency lower - more magnetic field, lower frequency and the plasma and gyro frequencies diverge. And there are several types of plasma waves - electron plasma and ion acoustic, Alfven - magnetosonic (the plasma vibrates lengthwise along the magnetic field). There are helical waves, spinors, right & left handed along the field, and of course there are hybrid modes. I've lost a few more hairs 8^( If there are thermal and density (acoustic) variation in the plasma, all kinds of kewl stuff can happen as self-interacting electrodynamic, acoustic and thermal shit happens. I'm fascinated with the idea of firing little plasma bubbles (spheromaks) with a microwave accelerator (waveguide accelerator). A plasma-rifle in the 40 joule range 8^) You could probably research plasma, fusion, and (microwave) accelerators on the web for years. Maybe someone will stick the right sized quartz or alumina tube with some washers or coils on it through there microwave oven, and some really kewl stuff shoot out at a few MeV. Or perhaps fire a rocket/jet engine down a weakly oscillating waveguide with plasma in it, and see the field significantly amplified (are HPM's ag'in the Geneva convention? What a great hunting weapon! A gun thats got no bang to scare off prey, no recoil, leaves no environmentaly unsafe lead, no bloody mess, sterilizes and cooks yer bird on site too!). Matlab must be good for something? > I saw an article from a car magazine where they tested various police radar > countermeasures. They said that some of them contained several fluorescent > tubes with wire wrapped around them (like you said) and they had no effect. > This is probably a case of something that would work if you made it very > carefully and energized the tube properly but has little chance of working > if you just throw it together in a plastic case. Maybe its snake oil, or maybe they didn't buy ads in the magazine. Traveling wave tubes are non-trivial devices. I'd just as soon try cooking a semiconductor, cuz its black art. But as far as a plasma intermodulating, any plasma heated with RF should intermodulate AFAIK. I remember a fox hunt I was on, where I used a switched dipole antenna. Just a diode (1N914/4148) switching between a couple 2 meter 1/2 wave dipoles. As a guy using it moved near the receiver, we could hear the switching frequency in a different receiver as the antenna's intermodulated signals . So re-radiating a signal (repeat-back jamming) isn't tough to spoof a dumb digital toy, but designing a negative resistance electron or plasma TWT is rocket science. I heard a can of rusty nails (iron oxide semiconductor) could cause a cell site to drop calls. But there your transmitting hundreds of watts, recieveing microwatts, and dropping calls if the SAT tone is messed up. That's the idea behind passive RFID transponders. Put a diode on a tuned circuit, the diode switched with a very low current micropower PIC, and interrogate it with a radar beam. Suppose any of those food packages we dropped over Afghanistan had similar tags for pilfering looters to signal those Specter Gunships? My I do ramble. Scott -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

>Maybe its snake oil, or maybe they didn't buy ads in the magazine. Traveling >wave tubes are non-trivial devices. I'd just as soon try cooking a >semiconductor, cuz its black art. But as far as a plasma intermodulating, >any plasma heated with RF should intermodulate AFAIK. I remember a fox hunt >I was on, where I used a switched dipole antenna. Just a diode (1N914/4148) >switching between a couple 2 meter 1/2 wave dipoles. As a guy using it moved >near the receiver, we could hear the switching frequency in a different >receiver as the antenna's intermodulated signals . So re-radiating a signal >(repeat-back jamming) isn't tough to spoof a dumb digital toy, but designing >a negative resistance electron or plasma TWT is rocket science. I heard a >can of rusty nails (iron oxide semiconductor) could cause a cell site to >drop calls. But there your transmitting hundreds of watts, recieveing >microwatts, and dropping calls if the SAT tone is messed up. That's the idea >behind passive RFID transponders. Put a diode on a tuned circuit, the diode >switched with a very low current micropower PIC, and interrogate it with a >radar beam. I have always thought that the ideal police radar jammer would be a length of microwave plumbing with PIN diodes across it at a critical point, probably several spaced at 1/4 wave intervals, and then driving the diodes from a current source so they switch off and on at a suitable audio frequency to represent a car at about 30mph. If the plumbing was long enough the radar unit may think there was two cars in the beam because of the time between echoes. I had even considered the possibility of having a U shaped piece of plumbing with a horn at each end running around the roof of the car to get the length! Totally passive device - if you can hear it officer you must be transmitting :) -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

From: "Alan B. Pearce" <spamBeGoneA.B.PearcespamBeGoneRL.AC.UK> Subject: Re: [EE]: 10GHz and fluorescent light > I have always thought that the ideal police radar jammer would be a length > of microwave plumbing with PIN diodes across it at a critical point, Switching the transmition line terminated in a significantly below-line impedance to above-line impedance, to create same and reversing polarity pulses (hope I got the polarities right!). >so they switch off and on at a suitable audio > frequency to represent a car at about 30mph. Better dither the frequency and inject audio noise. If there are other psychological speed queues, the cop might get suspicious. I hear in Texas their gettin medieval on truck drivers with just radar detectors. Obvious plumbing on the car wouldn't look good. > If the plumbing was long enough > the radar unit may think there was two cars in the beam because of the time > between echoes. I had even considered the possibility of having a U shaped > piece of plumbing with a horn at each end running around the roof of the car > to get the length! Might be a bit more elegant to use a loaded line with signifcantly lower phase velocity, ferrite (well, probably not above X-band) or glass or teflon. Then the line can be much shorter and smaller. I think they use to use mercury in acoustic delay lines for radar processing before the advent of SAW filters. Magnetic film technology for delay lines and matched filters is probably how the pro's do it. A negative resistance oscillator, (GaAs Fet's would probably be easier to work with than Gunn's) to amplify the reflected signal would help too. All that trouble when the cops are probably all using lasers now. You can spoof them too, just not as easy ;-) (low power) microwaves are just fun to play with anyway. Scott ******************************************************* If you are cheater #1 of 10, shame on you. If you are cheater #1 of 3, shame on your leaders, your culture, and shame on you if you're caught! ******************************************************* -- http://www.piclist.com hint: To leave the PICList TakeThisOuTpiclist-unsubscribe-requestEraseMEspam_OUTmitvma.mit.edu

----- Original Message ----- From: "Peter L. Peres" <RemoveMEplpTakeThisOuTACTCOM.CO.IL> Subject: Re: [EE]: 10GHz and fluorescent light > In the light of Alan B. Pearce's posting with PIN modulators the > flurescent light 'jammer' (with spiral around it) makes a lot of sense. Having a tuned waveguide just means that more energy gets a better match into and out of the modulator. > the fluorescent is driven with just the right frequency and the spiral is > tuned to the radar frequency it will become a AM modulated reflector. The spiral around the fluorescent tube hopes to exploit a negative resistance effect of the plasma. If the spiral and plasma are just right, plasma-maser instability or negative resistance means a bigger signal is re-radiated than is incident! But if you get it wrong, Landau damping absorbs incident energy and you get a hotter plasma. In effect, the plasma is an active transducer. The stream of current in the spiral tuned waveguide is like an air current across a read and tuned pipe - a whistle. > radar will be looking for doppler but maybe supermassive AM of the return > wave will cause it to produce that pseudo doppler harmonic in the radar > gun itself (either by intermodulation in the detector or by overriding the > FM limiter channel with too strong AM). Perhaps 'swamp' rather than 'supermassive' is a better term, and pseudo Doppler harmonic? And I've never heard of 'Doppler harmonics', but a hard-limited, FM limited, AM modulated signal would appear to be an FM signal, because the jittering edges of the signal would still contain the AM sidebands. The clipping would just create high-order harmonics. And a PLL detector will just lock on to the 'loudest' signal. Sorry about that stuff about repeat-back jamming which is useful in other contexts. Simple, (non pulsed or chirped) Doppler radar doesn't need it. > Hmm. Is it still legal if we know > how it works or does it have to be snake oil to be legal and work ? Or > some other combination ... What? ******************************************************* Is the American Identity freedom to pursue happiness and profit from the fruit of your own labors, or a servant leased to corporations by federal government that taxes you to your tolerance? ******************************************************* -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Hi Peter, Actually, I was comparing the signal strength of the echo from the light with the echo from my PC's power supply fan. I have not compared it to the signal from a car at the same distance. Since the discussion here, I was talking to a friend about this and he suggested that possibly what I am hearing is actually microwave noise emitted by the light(modulated by 120Hz), not an echo. Since the gunnplexer needs to be transmitting in order to receive anything (in order for the mixer diode to work it needs to be excited by the Gunn diode), the only way I can think to test this would be to put an isolator in the signal path between the horn antenna and the gunnplexer (so that the Gunn oscillator can still run, the gunnplexer can receive, but no signal will be emitted). However, I do not have an isolator for 10GHz so I can't run that test. Sean At 08:03 PM 2/28/02 +0200, you wrote: {Quote hidden}>Sean Breheny wrote that the signal he gets from the fluorescent light with >his Gunnplexer is several times stronger than the reflection from a car at >the same distance (or did I read it wrong). Maybe if the fluorescent would >have a wire wound on it to form a resonator/reflector at the Gunnplexer's >frequency the echo and modulation would be even stronger. > >Peter > >-- >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.

Sean Breheny wrote: > >Hi Peter, > > Actually, I was comparing the signal strength of the echo from the >light with the echo from my PC's power supply fan. I have not compared >it to the signal from a car at the same distance. > > Since the discussion here, I was talking to a friend about this and he >suggested that possibly what I am hearing is actually microwave noise >emitted by the light(modulated by 120Hz), not an echo. Since the >gunnplexer needs to be transmitting in order to receive anything (in >order for the mixer diode to work it needs to be excited by the Gunn >diode), the only way I can think to test this would be to put an >isolator in the signal path between the horn antenna and the gunnplexer >(so that the Gunn oscillator can still run, the gunnplexer can receive, >but no signal will be emitted). However, I do not have an isolator for >10GHz so I can't run that test. Maybe you can try the Fizeau trick to find out. Build a fast square wave oscillator and modulate the Gunn diode with it. You will need to put some distance between you and the lamp so the frequency becomes reasonable (20 meter band will do probably with the target at 10 meters). If there is no change in the tone between when the Gunn runs on DC and on AC then the source does not emit. If there is a change it emits. (obviously you use AC of a frequency such that the Gunn is on exactly when the reflected wave, that was emitted during the previous peak of AC, comes into the receiver. This means that the distance is 2 x d = lambda (of modulating frequency)). I have big doubts about the Hg lamp emitting microwaves of any kind (look up the Franck-Her(t)z (sp?) experiment) at room temperature. In my limited experience in the 10 GHz band (mostly satellite dish adjustments) fluorescents do not play a role as emitters. However they make a lot of noise in lower bands, up to 10-20MHz. You can see the RFI 'garbage' made by a fluorescent tube by holding a scope probe set on 10Meg and about 10mV/divY scale, 100ms/X directly to the glass (!) of the working tube. Ringing and negative resistance characteristic waveforms are very strongly present, often only on one half period's crest. Maybe in combination with the buffer gas (Argon or Helium) some sort of maser effect is possible in the fluorescents but I don't think so. Peter -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservEraseME.....mitvma.mit.edu with SET PICList DIGEST in the body