Schematics on Cell phone Blocker & Square Wave Generator
Square Wave Generator
The TL074 quad op-amp (U1) sweep generator of the cellular jammer exciter is based around a few simple op-amp building blocks. First, op-amp U1a is configured as a relaxation oscillator, or square wave generator. Basically, feedback resistor Rf charges capacitor C until it reaches a voltage level set by resistors R1 and R2. The op-amp then discharges, resulting in a waveform which is a square wave. The frequency of the square wave is determined via the following Perl equation:
# $FRQ is the oscillator's output frequency, in Hz
$Rf = 10000; # resistor Rf, in Ohms (10k)
$C1 = 0.00000001; # capacitor C1, in Farads (0.01 uF)
$R1 = 3300; # resistor R1, in Ohms (3.3k)
$R2 = 22000; # resistor R2, in Ohms (22k)
$FRQ = 1 / (2 * $Rf * $C1 * log(((2 * $R1) / ($R2) + 1)));
This equation is usually accurate only for a dual-supply op-amp configuration, (i.e. op-amps using both + and - voltages). A single-supply configuration will often output at a slightly higher frequency - and I'm not really sure why. It will help to experiment a bit.
The above values produce a frequency of approximately 19 kHz. "Real world" testing, however, showed the frequency to vary between 17-18 kHz. It reached 30 kHz when using a single-supply op-amp configuration. The component's exact value isn't too critical in this application. The main feedback resistor (Rf) is the main determining factor of the oscillator's frequency. Change it to a potentiometer (100k to 1M) to vary the output frequency. The other resistors in the oscillator control the duty cycle of the square wave, and for the most part can be left alone.
Integrator / Buffer
A square wave is pretty useless in a jamming circuit. Ideally, we want a "ramp" or "triangle" waveform. When applied to the voltage tune pin on an external Voltage Controlled Oscillator (VCO), the resulting RF output will be "swept" across the entire tuning band. This is what is neeed for wideband jamming applications.
In this particular circuit, op-amp U1b is configured as an integrator, or triange wave generator. The resistor (R4) and capacitor (C2)in the integrator op-amp's feedback network form a RC time constant which is used to convert the incoming square wave into a triangle wave. I actually found the best resulting output waveform by experimenting with different capacitor values in the feedback network (it will be frequency dependant). The feedback resistor (R4) should be approximately 10 times the input resistor (R3). A feedback capacitor value of 2200 pF was found to output the cleanest triangle waveform with minimum signal attenuation.
Mathematically, the integrator's components are found via the following Perl equations:
# $R4 is the integrator's feedback resistor, in Ohms
# $C2 is the integrator's feedback capacitor, in Farads
# $FRQ is the input square wave's frequency, in Hz
$R3 = 10000; # resistor R3, in Ohms (10k)
$R4 = 10 * $R3;
$C2 = 1 / ($FRQ * $R4);
But, I'd trust what an oscilloscope has to say more...
Op-amp U1c is configured as a buffer (gain = 1). This helps to isolate the oscillator network from the rest of the circuits. The series 0.1 µF capacitors remove any DC bias voltage which may be present on the op-amp's outputs. Low-leakage film capacitors will work the best.
Mixer / DC Offset
The final op-amp, U1d, is configured as a summing amplifier (gain = 1), otherwise known as a mixer. The output of a summing amplifier is the sum of the input voltages. The sum of these input voltages should not exceed the the +9 VDC of the TL074's positive voltage rail. The input to this mixer is a triangle wave and a random "noise" signal. These signals are mixed to form a new, "noisy" triangle waveform. When applied to the VCO, the resulting RF signal will "sweep" across the cellular downlink frequencies, and will be Frequency Modulated (FM) with the noise signal. This noise modulation helps to increase the jammer's effectiveness.
Another thing this op-amp performs is to provide a DC offset for the VCO's voltage tune pin. What this does is give the triangle wave a positive DC voltage offset to help "center" the triangle wave within the required frequency range.
Example:
(RF Output of a Particular VCO)
Voltage Tune (+ Volts DC) Frequency Output (MHz)
0 790
1 810
2 830
3 850
4 870
5 890
6 910
In our above example, a particular VCO is capable of tuning between 790 to 910 MHz with a voltage tune of 0 to +6 VDC. This works out to about 20 MHz of tuning per Volt. So, if a person wanted to "jam" the frequencies between 870 and 890 MHz, they would need a +1 Volt Peak-to-Peak triangle wave, with a DC offset of +4 Volts. This would result in voltage signal sweeping between +4 and +5 VDC (referenced from ground), sweeping the VCO RF output between 870 and 890 MHz. Of course, in real life, the voltages-to-frequency mappings are not this precise.
The DC offset is provided via two multiturn potentiometers. One provides a "coarse" tuning and the other, smaller value one provides the "fine" tuning. The use of multiturn potentiometers is not a requirement, but is highly recommended for ease of tuning.
Noise Generator
The noise generator is just a standard 6.8 Volt Zener diode with a small reverse current and a transistor buffer. The National LM386-1 audio amplifier acts as a natural band-pass filter and small-signal amplifier. The noise jamming signal is then mixed with the triangle wave input. This will help in masking the jamming transmission, making it look like random "noise" to an outside observer. Without the noise generator, the jamming signal is just a sweeping, unmodulated Continous Wave (CW) RF carrier.
The LM386-based noise generator may break into oscillation or output a very low signal. If it does this, adjust the Zener bias resistor (2 k) up or down a few hundred Ohms while observing the signal (disconnected from the LM386) on an oscilloscope for the maximum noise signal. Be sure that everything is grounded properly. The LM386 will oscillate without a good grounding system and poor power supply bypassing.
Any Zener diode above or equal to 6.2 Volts will work in the noise generator, as these Zener diodes have an "avalanche" region which generates a tremendous amount of noise when properly biased.
VCO
The Voltage Controlled Oscillator (VCO) is arguably the most important component in a cellular phone jamming system. It is little four-terminal device (Power, Ground, RF Output, and Voltage Tune) which generates the required, low-level RF output signal with a minimal of fuss. Unfortunately, they can be harder to find than a black man in Canada. Companies such as Mini-Circuits and Z-Communications are very helpful to amateur electronics enthusiasts, and will sell their VCO models in single quantities directly, or point you to a local distributor.
Ideally, the VCO you choose should cover the frequency range of the cellular base station's downlink frequencies (tower transmit) you wish to jam. You always jam a receiver, so in this case, you'd jam the mobile station's (handset) receive frequencies - which are the cellular tower's transmit frequencies.
Here's a little chart to help you choose the right cellular frequency ranges:
GSM / GPRS / HSCSD / EDGE
All TDMA formats.
Mainly used in Europe, Asia, Latin America, and North America. (MS) = Mobile Station Frequencies (BS) = Base Station FrequenciesGSM 450 Band
450.4 - 457.6 MHz (MS)
460.4 - 567.6 MHz (BS)
GSM 480 Band
478.8 - 486 MHz (MS)
488.8 - 496 MHz (BS)
GSM 750 Band
777 - 792 MHz (MS)
747 - 762 MHz (BS)
GSM 850 Band
824 - 849 MHz (MS)
869 - 894 MHz (BS)
GSM 900 Band
890 - 915 MHz (MS)
935 - 960 MHz (BS)
GSM 900 Extended Band
880 - 915 MHz (MS)
925 - 960 MHz (BS)
GSM 900 Railway Band
876 - 915 MHz (MS)
921 - 960 MHz (BS)
DCS 1800 Band
1710 - 1785 MHz (MS)
1805 - 1880 MHz (BS)
PCS 1900 Band
1850 - 1910 MHz (MS)
1930 - 1990 MHz (BS)
EIA-136 / EIA-95 / EIA-95A / EIA-95B / CDMA2000 / 1xEV-DO
EIA-136 is TDMA, the rest are CDMA formats.
Mainly used in North America, some Latin America, Korea, some Asian countries, Japan. (MS) = Mobile Station Frequencies (BS) = Base Station Frequencies800 MHz Systems
824 - 849 MHz (MS: US, Korea)
869 - 894 MHz (BS: US, Korea)
887 - 925 MHz (MS: Japan)
832 - 870 MHz (BS: Japan)
1900 MHz Systems
1850 - 1910 MHz (MS: US)
1930 - 1990 MHz (BS: US)
1750 - 1780 MHz (MS: Korea)
1840 - 1870 MHz (BS: Korea)
NMT 450 Band
411 - 483 MHz (MS)
421 - 493 MHz (BS)
NMT 2000 Band
1920 - 1980 MHz (MS)
2110 - 2170 MHz (BS)
W-CDMA / TD-SCDMA
Combination TDMA and CDMA formats.
Mainly used in North America, Europe, Korea, Japan, some Asian countries. (UE) = User Equipment Frequencies (BS) = Base Station FrequenciesIMT 2000 Band
1920 - 1980 MHz (UE)
2110 - 2179 MHz (BS)
PCS 1900 / W-CDMA Band
1850 - 1910 MHz (UE)
1930 - 1990 MHz (BS)
DCS 1800 Band
1710 - 1785 MHz (UE)
1805 - 1880 MHz (BS)
W-CDMA Band
1900 - 1920 MHz (UE/BS)
1910 - 1930 MHz (UE/BS)
2010 - 2025 MHz (UE/BS)
TD-SCDMA Band
2010 - 2025 MHz for TD-SCDMA mode.
GSM 900 and DCS 1800 for GSM mode.
The Global System for Mobile Communications (GSM) system was introduced in Europe around 1992. Its development and deployment went something like this:1910 - 1920s -
* U.S. Bell System develops first mobile radio telephone. It was the size of a large truck.
* Europe kills millions and millions of people.
1930s -
* U.S. Bell System continues development on the mobile radio telephone.
* Europe kills millions and millions of people.
1940s -
* U.S. Bell System stops development, uses copper to protect Europeans.
* Europe kills millions and millions of people.
1950s -
* U.S. Bell System develops first long-range VHF mobile telephones.
* Europe denies the whole Hitler thing.
Demands the U.S. protect, help, and feed them.
1960s -
* U.S. Bell System growing faster and faster, first radio telephone cellular network appear.
* Europe builds a wall.
1970s -
* U.S. cellular phones become common. AMPS standard is started.
* Europe wastes Marshall Plan money.
Does everything except build a Holocaust museum.
1980s -
* U.S. cellular phones become even more widespread, full country coverage.
* Europe sells weapons to hostile countries and terrorists.
Never repays any WWII debts or Marshall Plan money.
1990s -
* U.S. cellular phone starting to move to a new, superior CDMA format.
* Holy Shit! Europe develops GSM with Marshall Plan money, money they save
by denying the Holocaust, money the save by denying the whole Hitler thing,
money stolen from Jews, and by spying on the U.S.
2000s -
* U.S. has full coverage of a superior CDMA cellular format.
* Europe brags about their "advanced" cellular network technology, which ham radio
operators invented, and where using, 15 years earlier.
Crystek VCOs can be ordered in single quantities from Mouser Electronics for about $30 each.
Micronetics VCOs can be ordered in single quantities from Richardson Electronics for about $45 each.
Z-Communications VCOs can be ordered in single quantities from Richardson Electronics for about $20 each.
Mini-Circuits VCOs can be ordered in single quantities from Mini-Circuits' Small-Order Account hotline: (800) 214-6428 Ext. 606 (Dept. F).
RF Parts Company sells various RF power amplifier modules.
Picture 1 Picture of the prototype TL074 triangle wave generator.
Picture 2 Example oscilloscope picture of the raw TL074 triangle wave generator's output. Y = 1V, X = 20 µS.
Picture 3 Example oscilloscope picture of the LM386 noise generator's output. Y = 0.5V, X = 10 mS.
Picture 4 Example oscilloscope picture of the triangle wave output (1 Vpeak amplitude) with a 0V DC offset. Y = 2V, X = 0.1 mS.
Picture 5 Example oscilloscope picture of the triangle wave output (1 Vpeak amplitude) with an approximate 2.3V DC offset. Y = 2V, X = 0.1 mS.
Picture 6 Example oscilloscope picture of the triangle wave output (1 Vpeak amplitude) mixed with a 100 kHz sine wave, to simulate noise, and an approximate 4V DC offset. Y = 2V, X = 0.1 mS.
Picture 7 Example overview picture of the GBPPR JAMCAT. Noise generator is on the left-hand side.
posted by Underground CEO @ 8:04 AM
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