FROM: j.e.mcmillan@nospam.sheffield.ac.uk (John McMillan) SUBJECT: Re: Using a photomultiplier tube? DATE: Mon, 05 Feb 2001 12:31:01 +0000 ORGANIZATION: University of Sheffield NEWSGROUPS: sci.optics In article <3A7D8E56.786ECE2@hk.gin.net>, kt Chan wrote: > Ionization of gas produce light, photomultiplier can detect it. > Police can check if you install a radar alarm, the resonance circuit of the > receiver will absorb energy from the echo box and indict that you have one in > your car, it is illegal to process one in our area. > > Regards > > K.T.Chan You need an immense amount of radio energy (radar) to ionise gas. Air cherenkov experiments are simply not affected by radar and I do not believe that this technique can be used as a radar detector. Photomultiplier tubes were used as broad band noise sources for radar jammers - this is described in the RCA Photomultiplier Manual (now Burle PM Manual). jm FROM: kt Chan SUBJECT: Re: Using a photomultiplier tube? DATE: Mon, 05 Feb 2001 22:53:32 +0800 ORGANIZATION: Global Information Networks, http://news.hk.gin.net NEWSGROUPS: sci.optics John McMillan wrote: > In article <3A7D8E56.786ECE2@hk.gin.net>, kt Chan wrote: > > > Ionization of gas produce light, photomultiplier can detect it. > > Police can check if you install a radar alarm, the resonance circuit of the > > receiver will absorb energy from the echo box and indict that you have one in > > your car, it is illegal to process one in our area. > > > > Regards > > > > K.T.Chan > > You need an immense amount of radio energy (radar) to ionise gas. > Air cherenkov experiments are simply not affected by radar > and I do not believe that this technique can be used as a radar > detector. > > Photomultiplier tubes were used as broad band noise sources > for radar jammers - this is described in the RCA Photomultiplier > Manual (now Burle PM Manual). > > jm Look at http://www.seintl.com/prod.htm Geiger counter like. Regards K.T.Chan FROM: kt Chan SUBJECT: Re: Using a photomultiplier tube? DATE: Wed, 07 Feb 2001 19:51:31 +0800 ORGANIZATION: Global Information Networks, http://news.hk.gin.net NEWSGROUPS: sci.optics Sid Washer wrote: > << counter like.>>> > Yes, a nice line of X-ray and radiation detectors. > Nothing about radar; it's not their line. Is this one OK? http://www.c14dating.com/lsc.html FROM: j.e.mcmillan@nospam.sheffield.ac.uk (John McMillan) SUBJECT: Re: Using a photomultiplier tube? DATE: Wed, 07 Feb 2001 18:06:09 +0000 ORGANIZATION: University of Sheffield NEWSGROUPS: sci.optics In article <3A8136C3.A92EC843@hk.gin.net>, kt Chan wrote: > Is this one OK? > http://www.c14dating.com/lsc.html Yes, its fine. Its all about liquid scintillation counting for which photomultipliers are used a lot. Still nothing about radar though. Here's a quote from the RCA Photomultiplier Handbook - reprinted by Burle in 1980. ===================================================== Radar Jammer A totally unexpected application for the new photomultiplier tube occurred during World War II. The development of radar for detecting and tracking aircraft led to the simultaneous need for wideband electronic noise sources as radar jammers. Although other sources of noise were tried, the photomultiplier proved the most successful. The advantage of the tube was its high gain (10^7) and wide bandwidth (several hundred MHz). As a noise source the tube was operated with a non-modulated input light source and with high gain. The output amplifier photoelectric shot noise was "white" and thus indistinguishable from natural noise sources. This application of photomultiplier tubes resulted in production of thousands per month compared with previous production measured in only hundreds per year. ====================================================== FROM: Lou Boyd SUBJECT: Re: Using a photomultiplier tube? DATE: Tue, 06 Feb 2001 03:27:55 +0000 ORGANIZATION: Newsfeeds.com http://www.newsfeeds.com 80,000+ UNCENSORED Newsgroups. NEWSGROUPS: sci.optics Dan McKenna wrote: > > The photo multiplier was not used to detect the rf pulse but > to modulate (a.m.) a wide bandwidth transmitter (at the time) used > as a noise jammer. These days one would use a solid state noise diode. Using the PMT alone did a satisfactory job. With a couple of hundred volts between the last dynode and the anode and a dim light source on the cathode a 931A PMT can put out over a watt of white noise into an antenna with no additional amplifier. Do that with semiconductor diode! -- Lou Boyd Fairborn Observatory FROM: "Bob May" SUBJECT: Re: Using a photomultiplier tube? DATE: Tue, 6 Feb 2001 15:24:13 -0800 ORGANIZATION: Posted via Supernews, http://www.supernews.com NEWSGROUPS: sci.optics Might remind you that the power consumption of a diode is a lot less than the tube. That makes a watt of power easy for the tube but difficult for the solid state equivalant. All part of the greening of electronics so we can get more done on the same amount of source power. -- Bob May Remember that computers do exactly what you tell them to do, not what you think that you told them! Bob May FROM: "Joe Rongen" SUBJECT: Re: Using a photomultiplier tube? DATE: Tue, 6 Feb 2001 21:18:37 -0500 ORGANIZATION: http://extra.newsguy.com NEWSGROUPS: sci.optics "Lou Boyd" wrote in message news:3A7F6F3B.7AB9BDF0@fairborn.dakotacom.net... > Dan McKenna wrote: > > > > The photo multiplier was not used to detect the rf pulse but > > to modulate (a.m.) a wide bandwidth transmitter (at the time) used > > as a noise jammer. These days one would use a solid state noise > > diode. > > Using the PMT alone did a satisfactory job. With a couple of > hundred volts between the last dynode and the anode and a dim > light source on the cathode a 931A PMT can put out over a watt > of white noise into an antenna with no additional amplifier. > Never heard of that very inefficient method. I think at one time they used a small vibrating high-pressure mercury chamber with two or three connections. The output was much higher. ----- Regards Joe joe@alpha.to FROM: Lou Boyd SUBJECT: Re: Using a photomultiplier tube? DATE: Wed, 07 Feb 2001 03:46:05 +0000 ORGANIZATION: Newsfeeds.com http://www.newsfeeds.com 80,000+ UNCENSORED Newsgroups. NEWSGROUPS: sci.optics Joe Rongen wrote: > > Never heard of that very inefficient method. > I think at one time they used a small vibrating > high-pressure mercury chamber with two or > three connections. The output was much higher. I'm curious why you call the method "very inefficient" yet you say you never heard of it? A PMT is in fact a quite efficient broadband noise generator as it produces very fast impulses of moderately high energy for each electron emitted from the cathode. The rate of emission is random and the average rate is easily adjusted. If you allow efficiency in this case to be defined as radiated white noise divided by total input power I believe you would find a PMT to be competitive with any other method which was available during WW2. Little energy is wasted in the dynode string as each stage has power gain of about 5x. It is about efficient as any vacuum tube noise generator, and there is no filament to waste power. Using solid state devices could no doubt make a more compact and somewhat more efficient unit today mostly because the output frequency spectrum can be taylored more easily. There were higher power noise generators then, but PMT's were in fact used successfully as radar jammers in many US aircraft during WW2. -- Lou Boyd Fairborn Observatory FROM: "Joe Rongen" SUBJECT: Re: Using a photomultiplier tube? DATE: Wed, 7 Feb 2001 10:49:01 -0500 ORGANIZATION: http://extra.newsguy.com NEWSGROUPS: sci.optics "Lou Boyd" wrote in message news:3A80C4FD.6F6F2A33@fairborn.dakotacom.net... > Joe Rongen wrote: > > > > Never heard of that very inefficient method. > > I think at one time they used a small vibrating > > high-pressure mercury chamber with two or > > three connections. The output was much higher. > > I'm curious why you call the method "very inefficient" > yet you say you never heard of it? You did explain it with enough details, and yes it seems very inefficient. For jamming purposes one watt (like you wrote) is like a drop of water in the ocean. The idea of a radar jammer is to override all possible bands that the enemy may use. Brute force jamming of all frequencies over a wide spectrum is what counts. That small vibrating high-pressure mercury chamber with two or three connections gave an output of much more than a few watts. Compared to PMT's and associated circuitry, it was dirt cheap to produce and simple to install/setup - it did the job. But than again who can understand the military? It is common knowledge that they have a strange way of looking at life in general. ------- Regards Joe joe@alpha.to FROM: Dominic-Luc Webb molmed SUBJECT: Re: Using a photomultiplier tube? DATE: Fri, 9 Feb 2001 23:53:10 +0100 ORGANIZATION: Stockholm University NEWSGROUPS: sci.optics On Sun, 4 Feb 2001, kt Chan wrote: > A photomultiplier tube in the dark chamber can detect radio wave from the > radar, and trigger a counter radar apparatus. The receiver of radar signals > by a cavity is illegal, and police can check by an echo meter, not the > photomultiplier. This is sadly a dying art/science. I have electronics books from the 50's and 60's. Most of them describing tubes at all discuss this principle. It is interesting so many younger people who are skilled in electronics don't immediately see how PMTs could be used for jamming... Cheers, Dominic North 59 37' 30" East 17 48' 10"