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"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 |
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