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microwave oven magetron + pringle can antenna
Any suggestions on how to build a 2.4 GHz CW transmitter with a microwave
oven magnetron and a 2.4 GHz "pringle" or coffee can style antenna? There are tons of "pringle" or coffee can antennas or similar on the web. For example: http://flakey.info/antenna/waveguide or http://www.turnpoint.net/wireless/an...coffeecan.html I suppose one need only insert the magnetron antenna into the coffee can where one would normally mount the N-connector feed point. A labeled diagram of a microwave magnetron can be found at: http://www.gallawa.com/microtech/mag_test.html I suppose the metal coffee can has superior micro shielding properties relative to the aluminumized cardboard pringle can. Would I be better off with plumbing copper drain pipe from the stray RF exposure perspective? Since microwave magnetron use a half wave power supply, can I use two magnetrons in the same coffee can powered from a single AC HV transformer with a pair of HV rectifiers to feed alternate cycles to the magnetrons? Greg, VE0ACR |
Anchor wrote:
Any suggestions on how to build a 2.4 GHz CW transmitter with a microwave oven magnetron and a 2.4 GHz "pringle" or coffee can style antenna? There are tons of "pringle" or coffee can antennas or similar on the web. For example: http://flakey.info/antenna/waveguide or http://www.turnpoint.net/wireless/an...coffeecan.html I suppose one need only insert the magnetron antenna into the coffee can where one would normally mount the N-connector feed point. A labeled diagram of a microwave magnetron can be found at: http://www.gallawa.com/microtech/mag_test.html I suppose the metal coffee can has superior micro shielding properties relative to the aluminumized cardboard pringle can. Would I be better off with plumbing copper drain pipe from the stray RF exposure perspective? Since microwave magnetron use a half wave power supply, can I use two magnetrons in the same coffee can powered from a single AC HV transformer with a pair of HV rectifiers to feed alternate cycles to the magnetrons? Greg, VE0ACR The July 1989 73 had an article on using a microwave oven for ATV. It involved keeping most of the oven intact (including interlocks), with a blocking plate over the opening between the magnetron and the oven cavity and an e-field probe to couple the output to coax. Beyond that I know nothing. -- ------------------------------------------- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
Here is one guy which considers "weaponizing" one, perhaps there is data
there you can use... http://www.nettwerked.net/EM-HERF_Weapons_p1.txt There used to be a webpage which showed, in quite some detail, one hooked up to a hornfeed and used to attack neighbors in a new york apartment... I can't find it now... the picture detail was excellent though--had thought of constructing one to goof around with back then... Warmest regards, John "Anchor" wrote in message .. . Any suggestions on how to build a 2.4 GHz CW transmitter with a microwave oven magnetron and a 2.4 GHz "pringle" or coffee can style antenna? There are tons of "pringle" or coffee can antennas or similar on the web. For example: http://flakey.info/antenna/waveguide or http://www.turnpoint.net/wireless/an...coffeecan.html I suppose one need only insert the magnetron antenna into the coffee can where one would normally mount the N-connector feed point. A labeled diagram of a microwave magnetron can be found at: http://www.gallawa.com/microtech/mag_test.html I suppose the metal coffee can has superior micro shielding properties relative to the aluminumized cardboard pringle can. Would I be better off with plumbing copper drain pipe from the stray RF exposure perspective? Since microwave magnetron use a half wave power supply, can I use two magnetrons in the same coffee can powered from a single AC HV transformer with a pair of HV rectifiers to feed alternate cycles to the magnetrons? Greg, VE0ACR |
a pringle 'can' would probably arc and burn up. i would really worry about
side/rear lobes with coffee can antennas, even a minor lobe when working with kw levels at those frequencies could do some real damage in a short time... and reflections off nearby objects of the main lobe could really do a job on you. remember what those things are meant to do and be darn sure you don't end up looking like a bag of popcorn. "Anchor" wrote in message .. . Any suggestions on how to build a 2.4 GHz CW transmitter with a microwave oven magnetron and a 2.4 GHz "pringle" or coffee can style antenna? There are tons of "pringle" or coffee can antennas or similar on the web. For example: http://flakey.info/antenna/waveguide or http://www.turnpoint.net/wireless/an...coffeecan.html I suppose one need only insert the magnetron antenna into the coffee can where one would normally mount the N-connector feed point. A labeled diagram of a microwave magnetron can be found at: http://www.gallawa.com/microtech/mag_test.html I suppose the metal coffee can has superior micro shielding properties relative to the aluminumized cardboard pringle can. Would I be better off with plumbing copper drain pipe from the stray RF exposure perspective? Since microwave magnetron use a half wave power supply, can I use two magnetrons in the same coffee can powered from a single AC HV transformer with a pair of HV rectifiers to feed alternate cycles to the magnetrons? Greg, VE0ACR |
On Sun, 12 Jun 2005 17:39:36 -0700, John Smith wrote:
Here is one guy which considers "weaponizing" one, perhaps there is data there you can use... http://www.nettwerked.net/EM-HERF_Weapons_p1.txt There used to be a webpage which showed, in quite some detail, one hooked up to a hornfeed and used to attack neighbors in a new york apartment... I can't find it now... the picture detail was excellent though--had thought of constructing one to goof around with back then... Warmest regards, John That web site is a joke, isn't it??? |
"Anchor" wrote in message .. . Any suggestions on how to build a 2.4 GHz CW transmitter with a microwave oven magnetron and a 2.4 GHz "pringle" or coffee can style antenna? There are tons of "pringle" or coffee can antennas or similar on the web. For example: http://flakey.info/antenna/waveguide or http://www.turnpoint.net/wireless/an...coffeecan.html I suppose one need only insert the magnetron antenna into the coffee can where one would normally mount the N-connector feed point. A labeled diagram of a microwave magnetron can be found at: http://www.gallawa.com/microtech/mag_test.html I suppose the metal coffee can has superior micro shielding properties relative to the aluminumized cardboard pringle can. Would I be better off with plumbing copper drain pipe from the stray RF exposure perspective? Since microwave magnetron use a half wave power supply, can I use two magnetrons in the same coffee can powered from a single AC HV transformer with a pair of HV rectifiers to feed alternate cycles to the magnetrons? Greg, VE0ACR I once looked at a microwave oven on a spectrum analyzer (Loosely coupled near the door seal). The signal was spread over 100s of MHz. It also appeared to be pulsed. The spectrum, however, did not look like the expected Sa(x) distribution. Magnetrons are not noted for their stability, and are probably not suitable for CW. I have played with tunable 500 mW klystrons, and they can drift 10s of MHz (at 12 GHz), in a very short period of time. 73, Frank |
Frank wrote:
snip I once looked at a microwave oven on a spectrum analyzer (Loosely coupled near the door seal). The signal was spread over 100s of MHz. It also appeared to be pulsed. The spectrum, however, did not look like the expected Sa(x) distribution. Magnetrons are not noted for their stability, and are probably not suitable for CW. I have played with tunable 500 mW klystrons, and they can drift 10s of MHz (at 12 GHz), in a very short period of time. 73, Frank In the article I quoted above they tune the magnetron frequency by varying the voltage to the magnetron. I wouldn't be surprised if the oven's DC to the magnetron was filtered lightly or not at all. -- ------------------------------------------- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
I would think a 1KW or greater magnetron run off a non-filtered and
particularly dirty, but rectified dc supply (you could even feed a ramp or triangle dc power wave to the magnetron to cause frequency sweep) and into a sloppy waveguide exhibiting multiple resonant frequencies would knock out all cell phone and wireless communications on shf+ freqs for blocks if not miles... you would probably start jamming the cell towers for miles around and have every "pirate transmitter" hunter in America on your tail... in a large city/metro area you would cause havoc to break out--this WOULD BE ONE SERIOUS OFFENSE!!! If caught, you would learn to call prison your home! And Bruce, in the cell next to you, would fall in love with you! Not to mention the danger of exposure to the freqs in question--this would be best left alone... John "Anchor" wrote in message .. . Any suggestions on how to build a 2.4 GHz CW transmitter with a microwave oven magnetron and a 2.4 GHz "pringle" or coffee can style antenna? There are tons of "pringle" or coffee can antennas or similar on the web. For example: http://flakey.info/antenna/waveguide or http://www.turnpoint.net/wireless/an...coffeecan.html I suppose one need only insert the magnetron antenna into the coffee can where one would normally mount the N-connector feed point. A labeled diagram of a microwave magnetron can be found at: http://www.gallawa.com/microtech/mag_test.html I suppose the metal coffee can has superior micro shielding properties relative to the aluminumized cardboard pringle can. Would I be better off with plumbing copper drain pipe from the stray RF exposure perspective? Since microwave magnetron use a half wave power supply, can I use two magnetrons in the same coffee can powered from a single AC HV transformer with a pair of HV rectifiers to feed alternate cycles to the magnetrons? Greg, VE0ACR |
"John Smith" wrote in message ... I would think a 1KW or greater magnetron run off a non-filtered and particularly dirty, but rectified dc supply (you could even feed a ramp or triangle dc power wave to the magnetron to cause frequency sweep) and into a sloppy waveguide exhibiting multiple resonant frequencies would knock out all cell phone and wireless communications on shf+ freqs for blocks if not miles... you would probably start jamming the cell towers for miles around and have every "pirate transmitter" hunter in America on your tail... in a large city/metro area you would cause havoc to break out--this WOULD BE ONE SERIOUS OFFENSE!!! If caught, you would learn to call prison your home! And Bruce, in the cell next to you, would fall in love with you! Not to mention the danger of exposure to the freqs in question--this would be best left alone... Interesting paper concerning microwave magnetrons at http://www-personal.engin.umich.edu/...laes_tps04.pdf Mention is made of magnetron cavity Qs in excess of 200. The spectral width of such a source, at the 3 dB points, would therefore be about 12 MHz. Not really suitable for CW, but far better than my observations. Comments about poor power supplies are probably correct. It is interesting to note that the spectral purity of oven magnetrons is of concern with regards to interference to the 2.4 GHz ISM band. There are techniques for the stabilization of magnetrons when used for Moving Target Indication (MTI) on RADAR systems. The fact is it is very easy to build a high stability synthesizer -- with spectral widths of the order of 1 or 2 Hz -- at 2.4 GHz. Amplification is another matter, since a 2.4 GHz TWT probably costs around $7,000. 73, Frank |
In article ,
"John Smith" wrote: I would think a 1KW or greater magnetron run off a non-filtered and particularly dirty, but rectified dc supply (you could even feed a ramp or triangle dc power wave to the magnetron to cause frequency sweep) and into a sloppy waveguide exhibiting multiple resonant frequencies would knock out all cell phone and wireless communications on shf+ freqs for blocks if not miles... you would probably start jamming the cell towers for miles around and have every "pirate transmitter" hunter in America on your tail... in a large city/metro area you would cause havoc to break out--this WOULD BE ONE SERIOUS OFFENSE!!! If caught, you would learn to call prison your home! And Bruce, in the cell next to you, would fall in love with you! Not to mention the danger of exposure to the freqs in question--this would be best left alone... John Bull****, a 2.4 Ghz Magnitron would NOT cause any problems for any 800 Mhz or even any 1.8 Ghz cellphone system no matter how bad the powersupply was filtered. This just doesn't COMPUTE, even in another world, lifetime, or dimension. Me |
Me:
Oh really, so if part of the waveguide is made resonant at 800 MHz and I am striking it with a "1KW hammer" it will not "ring" at all? Funny, but that runs against all I have seen here in the real world... John "Me" wrote in message ... In article , "John Smith" wrote: I would think a 1KW or greater magnetron run off a non-filtered and particularly dirty, but rectified dc supply (you could even feed a ramp or triangle dc power wave to the magnetron to cause frequency sweep) and into a sloppy waveguide exhibiting multiple resonant frequencies would knock out all cell phone and wireless communications on shf+ freqs for blocks if not miles... you would probably start jamming the cell towers for miles around and have every "pirate transmitter" hunter in America on your tail... in a large city/metro area you would cause havoc to break out--this WOULD BE ONE SERIOUS OFFENSE!!! If caught, you would learn to call prison your home! And Bruce, in the cell next to you, would fall in love with you! Not to mention the danger of exposure to the freqs in question--this would be best left alone... John Bull****, a 2.4 Ghz Magnitron would NOT cause any problems for any 800 Mhz or even any 1.8 Ghz cellphone system no matter how bad the powersupply was filtered. This just doesn't COMPUTE, even in another world, lifetime, or dimension. Me |
'Course, there is a method of running a STABLE SOURCE , relatively
low power , coupled to a microwave oscillator source, and locking it to a the frequency of the stable source- tho don't know if it works with Magnetrons-- does with klystrons, and Tuned Grid-Tuned Plate oscs, tho! Jim NN7K Me wrote: In article , "John Smith" wrote: I would think a 1KW or greater magnetron run off a non-filtered and particularly dirty, but rectified dc supply (you could even feed a ramp or triangle dc power wave to the magnetron to cause frequency sweep) and into a sloppy waveguide exhibiting multiple resonant frequencies would knock out all cell phone and wireless communications on shf+ freqs for blocks if not miles... you would probably start jamming the cell towers for miles around and have every "pirate transmitter" hunter in America on your tail... in a large city/metro area you would cause havoc to break out--this WOULD BE ONE SERIOUS OFFENSE!!! If caught, you would learn to call prison your home! And Bruce, in the cell next to you, would fall in love with you! Not to mention the danger of exposure to the freqs in question--this would be best left alone... John |
"John Smith" wrote in message ... Me: Oh really, so if part of the waveguide is made resonant at 800 MHz and I am striking it with a "1KW hammer" it will not "ring" at all? Funny, but that runs against all I have seen here in the real world... John A waveguide can be considered a very wide bandpass filter. Any frequency coupled to the waveguide, within its pass-band, will appear at the output of the waveguide. There will be no spurious signals attributed to the waveguide. As mentioned previously; measurements I have made on microwave oven magnetrons indicate an extremely wideband, highly unstable signal, covering hundreds of MHz either side of the nominal 2.45 GHz. The potential for interference to other services, particularly the 2.4 GHz ISM band, and to a lesser extent, the 1.9 GHz cell frequencies, is fairly high. It is doubtful that any significant energy will be present at 800 MHz. The relative spectral purity of the magnetron measured in http://www-personal.engin.umich.edu/...laes_tps04.pdf probably used a laboratory grade 4kV power supply. Note, however, that significant 120 MHz sidebands (and harmonics) are present. Frank |
.... if I was to attempt to jam that broad of range of freqs, I would
couple it to a waveguide which exhibited resonance on that whole spectrum (feed the center of circular guide/"modified horn" with shortest point to edge of circle resonant at 2.4 ghz resonant, longest point to edge of circle resonant at 800 mhz) , feeding the magnetron a ramp or triangle dc voltage/current of 1 mhz freq--is going to generate harmonics until the cows come home... I would feel like Dr. Frankenstein when the neighbors showed up on my door step with their pitchforks and scythes!!! Warmest regards, John "Frank" wrote in message news:obNre.54658$on1.13081@clgrps13... "John Smith" wrote in message ... Me: Oh really, so if part of the waveguide is made resonant at 800 MHz and I am striking it with a "1KW hammer" it will not "ring" at all? Funny, but that runs against all I have seen here in the real world... John A waveguide can be considered a very wide bandpass filter. Any frequency coupled to the waveguide, within its pass-band, will appear at the output of the waveguide. There will be no spurious signals attributed to the waveguide. As mentioned previously; measurements I have made on microwave oven magnetrons indicate an extremely wideband, highly unstable signal, covering hundreds of MHz either side of the nominal 2.45 GHz. The potential for interference to other services, particularly the 2.4 GHz ISM band, and to a lesser extent, the 1.9 GHz cell frequencies, is fairly high. It is doubtful that any significant energy will be present at 800 MHz. The relative spectral purity of the magnetron measured in http://www-personal.engin.umich.edu/...laes_tps04.pdf probably used a laboratory grade 4kV power supply. Note, however, that significant 120 MHz sidebands (and harmonics) are present. Frank |
"John Smith" wrote in message
... ... if I was to attempt to jam that broad of range of freqs, I would couple it to a waveguide which exhibited resonance on that whole spectrum (feed the center of circular guide/"modified horn" with shortest point to edge of circle resonant at 2.4 ghz resonant, longest point to edge of circle resonant at 800 mhz) , feeding the magnetron a ramp or triangle dc voltage/current of 1 mhz freq--is going to generate harmonics until the cows come home... I would feel like Dr. Frankenstein when the neighbors showed up on my door step with their pitchforks and scythes!!! Warmest regards, John Not sure how the magnetron would respond to a ramp, but at some amplitude the magnetron would cease oscillations. The fact is that the harmonic decay of a sawtooth waveform is slightly higher than a rectangular pulse. A worst case analysis would involve a rectangular pulse with a finite rise/fall time. If for example the magnetron were pulsed with a square wave, 50% duty cycle, at 1 MHz, with a rise time of 10nS, the 1,600 th harmonic (i.e. lower sideband at 800 MHz) amplitude is about -50 dBC. This result is obtained from the solution of the products of two Sa(x) functions involving the rise time, period, and pulse width of a symmetrical trapezoidal waveform. If you have a burning desire to know, I can vary the parameters of rise time, pulse width, etc. to see how the spectral shape changes. These sidebands, in the vicinity of 800 MHz, are therfore of significant amplitude. I am, however, fairly certain that 800 MHz is below the waveguide cut-off frequency. I will try and measure the dimensions of a typical oven waveguide to determine its cut-off frequency. The other factor is the Q of the magnetron cavities how would this effect the banwidth of the spectrum? Since the magnetron is coupled to the waveguide from a probe in one of its cavities, I would think that the higher sidebands would be significantly reduced. Possibly you have made measurements on such a system. The math, at least, does indicate the potential of building a very wide band jammer -- probably not a good idea! 73, Frank |
.... no need, I have seen the results of such devices in practical
operation... I do a class at the jr. college here, have 3 sons in the computer field, my garage is a clubhouse/wireless point/computer lab... .... lot of cs/electronics majors... they have fired up such devices before I said, "Not here!!!" Really got ****ed when it jammed my "late night talk radio" which I fall asleep to... Warmest regards, John "Frank" wrote in message news:37_re.49668$wr.42366@clgrps12... "John Smith" wrote in message ... ... if I was to attempt to jam that broad of range of freqs, I would couple it to a waveguide which exhibited resonance on that whole spectrum (feed the center of circular guide/"modified horn" with shortest point to edge of circle resonant at 2.4 ghz resonant, longest point to edge of circle resonant at 800 mhz) , feeding the magnetron a ramp or triangle dc voltage/current of 1 mhz freq--is going to generate harmonics until the cows come home... I would feel like Dr. Frankenstein when the neighbors showed up on my door step with their pitchforks and scythes!!! Warmest regards, John Not sure how the magnetron would respond to a ramp, but at some amplitude the magnetron would cease oscillations. The fact is that the harmonic decay of a sawtooth waveform is slightly higher than a rectangular pulse. A worst case analysis would involve a rectangular pulse with a finite rise/fall time. If for example the magnetron were pulsed with a square wave, 50% duty cycle, at 1 MHz, with a rise time of 10nS, the 1,600 th harmonic (i.e. lower sideband at 800 MHz) amplitude is about -50 dBC. This result is obtained from the solution of the products of two Sa(x) functions involving the rise time, period, and pulse width of a symmetrical trapezoidal waveform. If you have a burning desire to know, I can vary the parameters of rise time, pulse width, etc. to see how the spectral shape changes. These sidebands, in the vicinity of 800 MHz, are therfore of significant amplitude. I am, however, fairly certain that 800 MHz is below the waveguide cut-off frequency. I will try and measure the dimensions of a typical oven waveguide to determine its cut-off frequency. The other factor is the Q of the magnetron cavities how would this effect the banwidth of the spectrum? Since the magnetron is coupled to the waveguide from a probe in one of its cavities, I would think that the higher sidebands would be significantly reduced. Possibly you have made measurements on such a system. The math, at least, does indicate the potential of building a very wide band jammer -- probably not a good idea! 73, Frank |
"John Smith" wrote in message ... ... no need, I have seen the results of such devices in practical operation... I do a class at the jr. college here, have 3 sons in the computer field, my garage is a clubhouse/wireless point/computer lab... ... lot of cs/electronics majors... they have fired up such devices before I said, "Not here!!!" Really got ****ed when it jammed my "late night talk radio" which I fall asleep to... Warmest regards, John When people try to say you are talking garbage it sparks my curiosity, and have to see for myself. I should have realized that Sa(x) almost goes on forever. Even at 100 GHz from the carrier the sidebands are about -85 dBc. Other factors will probably suppress these very high order sidebands, but still interesting to crunch numbers. Now I have an overwhelming desire to build a -4000 V pulse generator, just to see how close it comes to theory. 73, Frank |
Frank:
Lol, it is catching huh? Almost without doubt, what was tearing up my am radio was the signal being fed on the B+ rail (~1Mhz run by a "chopped" supply--and most likely leaking some signal onto the house mains--I am guilty of not making those suspicions clear)... however, their intent was to jam wireless wans/lans--from what I heard--they were/are more than successful... I know there was great experimentation here in trying to get a microwave magnetron "rock stable"--when that failed it lead to the "other" experimentation... Just in case there is something to this--be careful when and where you operate it...I think it just might surprise you... Warmest regards, John "Frank" wrote in message news:Rx%re.49680$wr.38116@clgrps12... "John Smith" wrote in message ... ... no need, I have seen the results of such devices in practical operation... I do a class at the jr. college here, have 3 sons in the computer field, my garage is a clubhouse/wireless point/computer lab... ... lot of cs/electronics majors... they have fired up such devices before I said, "Not here!!!" Really got ****ed when it jammed my "late night talk radio" which I fall asleep to... Warmest regards, John When people try to say you are talking garbage it sparks my curiosity, and have to see for myself. I should have realized that Sa(x) almost goes on forever. Even at 100 GHz from the carrier the sidebands are about -85 dBc. Other factors will probably suppress these very high order sidebands, but still interesting to crunch numbers. Now I have an overwhelming desire to build a -4000 V pulse generator, just to see how close it comes to theory. 73, Frank |
"John Smith" wrote in message
... Frank: Lol, it is catching huh? Almost without doubt, what was tearing up my am radio was the signal being fed on the B+ rail (~1Mhz run by a "chopped" supply--and most likely leaking some signal onto the house mains--I am guilty of not making those suspicions clear)... however, their intent was to jam wireless wans/lans--from what I heard--they were/are more than successful... I know there was great experimentation here in trying to get a microwave magnetron "rock stable"--when that failed it lead to the "other" experimentation... Just in case there is something to this--be careful when and where you operate it...I think it just might surprise you... Warmest regards, John When the microwave oven is running it interferes with my 200 kHz (conducted over house wiring) intercom system (Rat Shack). I suspected that it was noise from the power supply, and not the actual magnetron. I am still inclined to believe that the selectivity of the magnetron cavities will limit the modulated spectrum, not to mention the waveguide cut-off frequency. If I get a chance I will look more carefully at the RF output on a spectrum analyzer. As for magnetron frequency stability and phase noise performance, I remember COHO/STALO MTI RADAR, and thought that the magnetron was stabilized. This is not true, as explained in http://www.alphalpha.org/radar/coho_e.html The only way I can conceive of stabilizing is by the use of a tunable magnetron and AFC system. Then there is also the possibility of injection locking. 73, Frank |
Reading the responses, some valid, some not*, I guess the best
thing to try is: o illuminate a surplus TVRO 12 ft dish with the magnetron - collect and focus side lobes - 36+ dbi gain o use a regulated power supply the decrease the bandwidth o use some form of bandpass filtering such as cavity resonators o point the thing at the moon and listen for echos o experiment using it as a ground mapping radar I vaguely recall seeing something in a late 80's (?) magazine, may be 73 or CQ VHF, that built a digital data link from a pair of 2 mbit PC network cards and a magnetron. * FYI: o GSM cell phone bands = 850/1900 MHz for the Americas, 900/1850 MHz outside the Americas, not 2.4 GHz. o microwave ovens with the door closed already interfere with most 2.4 GHz ISM band FCC Part 15 devices in close proximity |
"Anchor" wrote in message
.. . Reading the responses, some valid, some not*, I guess the best thing to try is: o illuminate a surplus TVRO 12 ft dish with the magnetron - collect and focus side lobes - 36+ dbi gain o use a regulated power supply the decrease the bandwidth o use some form of bandpass filtering such as cavity resonators o point the thing at the moon and listen for echos o experiment using it as a ground mapping radar I vaguely recall seeing something in a late 80's (?) magazine, may be 73 or CQ VHF, that built a digital data link from a pair of 2 mbit PC network cards and a magnetron. * FYI: o GSM cell phone bands = 850/1900 MHz for the Americas, 900/1850 MHz outside the Americas, not 2.4 GHz. o microwave ovens with the door closed already interfere with most 2.4 GHz ISM band FCC Part 15 devices in close proximity The problem with the spectral width, and stability, of the magnetron limits is usefulness for low signals. As mentioned before, see http://www-personal.engin.umich.edu/...laes_tps04.pdf Now I know what you are doing you might consider a "COHO/STALO" system, as used in MTI RADARs, see http://www.alphalpha.org/radar/coho_e.html With COHO/STALO, you could probably reduce the BW to near 1 Hz with digital filtering. You may also consider applying the free-space RADAR equation, to determine the feasibility. With a nominal ERP of 4 MW you may be successful without using COHO/STALO. Try pulsing the magnetron with a very low PRF, and use an "A" scan monitor. Regards, Frank |
In article ,
Anchor wrote: * FYI: o microwave ovens with the door closed already interfere with most 2.4 GHz ISM band FCC Part 15 devices in close proximity Agreed, and it's not too surprising. The FCC doesn't regulate microwave oven leakage, and the FDA's standard limits leakage for an installed microwave oven to 5 milliwatts per cm^2 at a distance of 5 cm from the surface. I've read that a fairly high percentage of older microwave ovens leak more than the standard would allow. That level could add up pretty quickly... a watt or more of leakage from an older microwave oven would not surprise me very much. A 15-milliwatt Part 15 device can't compete. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
Frank,
Thanks for the advise. Obviously if it was trivial to modify magnetrons for communications in the 13 cm S band, there would be a lot of high power activity on that band and fewer dead microwave ovens in landfill sites. Surely a near KW of radio energy can be used for more than re-warming left-overs. Maybe not. |
Here is an excellent and practical discussion of rough design and
practical use of can antennas, make sure to follow the link on the bottom of the page... http://www.turnpoint.net/wireless/an...coffeecan.html John "Anchor" wrote in message .. . Any suggestions on how to build a 2.4 GHz CW transmitter with a microwave oven magnetron and a 2.4 GHz "pringle" or coffee can style antenna? There are tons of "pringle" or coffee can antennas or similar on the web. For example: http://flakey.info/antenna/waveguide or http://www.turnpoint.net/wireless/an...coffeecan.html I suppose one need only insert the magnetron antenna into the coffee can where one would normally mount the N-connector feed point. A labeled diagram of a microwave magnetron can be found at: http://www.gallawa.com/microtech/mag_test.html I suppose the metal coffee can has superior micro shielding properties relative to the aluminumized cardboard pringle can. Would I be better off with plumbing copper drain pipe from the stray RF exposure perspective? Since microwave magnetron use a half wave power supply, can I use two magnetrons in the same coffee can powered from a single AC HV transformer with a pair of HV rectifiers to feed alternate cycles to the magnetrons? Greg, VE0ACR |
Thanks for the advise.
Obviously if it was trivial to modify magnetrons for communications in the 13 cm S band, there would be a lot of high power activity on that band and fewer dead microwave ovens in landfill sites. Surely a near KW of radio energy can be used for more than re-warming left-overs. Maybe not. No problem, glad to help. It still might be interesting to plug in the parameters to the free space radar equation, considering receiver noise figure, and signal BW, etc.. I am sure there is data available on the reflectivity of the Lunar surface. Of course COHO/STALO will only work if you are receiving your own signal, so not much use if you are attempting to work others. As I suspected, some work has been done on the injection locking of magnetrons; as in http://www.lancs.ac.uk/cockcroft-ins...ul04/tahir.pdf This presentation recommends an injection signal of 2% power, or 20 W in the case of a 1 kW magnetron. I have no experience on solid state amplifiers at such a frequency (except for TWTs), but the construction of a single loop synthesizer using ,a National Semiconductor chip, and a Z-Communications (or Mini-Circuits etc.) SMT oscillator is trivial. There are lots of eval. boards available for a nominal cost. I think Z-comm. has one, but have not priced it recently. I guess such projects are a bit impractical unless you have a good spectrum analyzer 73, Frank |
Found the following interesting site: http://www.df9cy.de/pathloss.htm
There is a downloadable spread sheet concerning moon-bounce path loss. I have not verified the accuracy of the spread sheet, but it looks reasonable: From the spread sheet, if you plug in the following parameters: Power 1 kW; BW 3 MHz; Antenna gain 35 dB; Frequency 2.4 GHz and many more, such as noise figure, etc. The received signal will be 40 dB below the noise. Reducing the bandwidth to 100 Hz the signal will be about 4 dB above the noise -- as 10*log(BW1/BW2) will confirm. Reduction in bandwidth to between 1 and 10 Hz would seem to be desirable. Stability required is about 0.0004 ppm, not to mention degradation due to TCXO 1/f noise. Frank |
One consideration is that Magnetrons are NOT designed, normally for ccs
service-- they are designed for "PULSE" service, even the ovens- (duty cycle of MUCH less then even .5) and, pulse transmissions arn't looked favorably on many of the microwave bands any more. Anchor wrote: Frank, Thanks for the advise. Obviously if it was trivial to modify magnetrons for communications in the 13 cm S band, there would be a lot of high power activity on that band and fewer dead microwave ovens in landfill sites. Surely a near KW of radio energy can be used for more than re-warming left-overs. Maybe not. |
"Jim - NN7K" wrote in message
m... One consideration is that Magnetrons are NOT designed, normally for ccs service-- they are designed for "PULSE" service, even the ovens- (duty cycle of MUCH less then even .5) and, pulse transmissions arn't looked favorably on many of the microwave bands any more. Sorry if I am repeating stuff that you may have seen before, but I have noticed things that do not seem to add up. For example the paper at: http://www-personal.engin.umich.edu/...aes_tps04.pdf; Shows the CW output of the magnetron spectrum as -10 dBm. Since for the output is monitored via a 30 dB coupler, and a 30 dB attenuator I would have expected the amplitude to be 0 dBm. It is hard to imagine such testing being done with a grossly overheated magnetron. Having observed the output of a microwave oven on a spectrum analyzer, it did appear to be pulsed, although the spectrum was more characteristic of a frequency hopping (or swept) signal. Frank |
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