the7thguest
10-11-2006, 02:14 AM
If you set up an FM modulation system with the carrier around the same frequancy as the mid GSM(ish) freq, and then modulate that with a sine wave of enough amplitude you should be able to "over modulate" (which may be the wrong choiuce of words as its what you want to do) you should in theory be able to bottom out around the lower GSM limits and go all the way up to the upper limits of the band... I feel some maths coming along...
FM Modulation: http://en.wikipedia.org/wiki/FM
Frequancy Deviation: AF
Voltage Deviation: AV
Rated System Deviation: Fd
Frequency Deviation Constant: k, k=AF/Fd
Modular Sensitivity: AF/AV
Modulation Index: Mf, Mf = AF/Fm = (k * Fd)/Fm
Deviation Ratio: D, D= (Fd)/(Fm Max)
Carson's Rule for calculating FM Bandwidth...
BW = 2(fm + AF) - OR - BW = 2(Fm + k * Fd) * Fm
Which basicly means that if you can design a say... PLL carrier generator & a suitable modulation system, you could in theory modulate your carrier, with your carrier therefore transmit no relevant information, and by doing so at a suitable voltage you would have a system that would transmit noise across a broad spectrum essentially blacking out relevant bands such as GSM, GPS, WiFi etc...
Due to the nature of radio though, one would have to be very careful to apply proper filtering to ensure that your not going to be causing interferance to other bands... cos that would be bad karma...
Cheers!
FM Modulation: http://en.wikipedia.org/wiki/FM
Frequancy Deviation: AF
Voltage Deviation: AV
Rated System Deviation: Fd
Frequency Deviation Constant: k, k=AF/Fd
Modular Sensitivity: AF/AV
Modulation Index: Mf, Mf = AF/Fm = (k * Fd)/Fm
Deviation Ratio: D, D= (Fd)/(Fm Max)
Carson's Rule for calculating FM Bandwidth...
BW = 2(fm + AF) - OR - BW = 2(Fm + k * Fd) * Fm
Which basicly means that if you can design a say... PLL carrier generator & a suitable modulation system, you could in theory modulate your carrier, with your carrier therefore transmit no relevant information, and by doing so at a suitable voltage you would have a system that would transmit noise across a broad spectrum essentially blacking out relevant bands such as GSM, GPS, WiFi etc...
Due to the nature of radio though, one would have to be very careful to apply proper filtering to ensure that your not going to be causing interferance to other bands... cos that would be bad karma...
Cheers!