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Many used car dealers often install long-term GPS tracking systems, the purpose is self-evident. Therefore, signal jammers and signal detectors become popular equipment.

GPS signal jammer are small, high-power radio frequency (RF) transmitters that interfere with legitimate communication devices (cell phones, GPS, Wi-Fi networks, and toll readers).

It emits radio frequency signals at the same frequency as GPS signals, causing interference and preventing GPS devices from receiving accurate signals. This interference can cause GPS devices to lose their connection to GPS satellites, making it impossible to track their position or receive accurate location information. gps jammer are illegal in many countries, including the United States, because they can disrupt the operation of emergency services and other vital systems that rely on GPS signals. Using GPS jammers can also be dangerous and can lead to accidents, especially in industries such as aviation and navigation.

GPS receivers rely on low-power microwave signals broadcast by GPS satellites. GPS signal jammers work by overwhelming these satellite signals with radio signals of higher power but shorter range, creating "noise" that causes the GPS receiver to be unable to accurately calculate its position.

GPS jammers are small, portable and easy to operate. Anyone who wants to disrupt the operation of GPS devices or systems can buy them online and use them.

What does a GPS jammer look like?

Because the devices that can block GPS come from a number of manufacturers, they vary widely in shape, size and dimensions, making them difficult to spot inside a driver's vehicle. Most commonly, GPS interceptors operate over short distances and are small enough to plug into a power source such as a cigarette lighter or iPhone and intercept signals from GPS trackers installed in the cockpit of a vehicle.

Some GPS jammers look like small black boxes or cylindrical devices with antennas, while others are designed to look like everyday items like cell phone chargers or USB drives.

Handheld GPS jammers are usually small and easy to carry. They usually have a small built-in battery that is used to interfere with GPS signals from nearby devices. Larger GPS jammers are typically used on vehicles, boats, or buildings and are designed to cover a larger area or distance.

Cigarette lighter GPS jammer structure

Making a DIY GPS jammer for your car tracker is not an easy task, as it requires a deep understanding of the fundamentals. However, if you are determined to build one, you can disassemble a simple GPS jammer as a reference.

The weakness of GPS signals makes it easy for low-cost jammers to jam them. These jammers do not attempt to mimic GPS satellites, but transmit loud enough noise to drown out the real signal. As a result, legitimate satellite signals become undetectable. When the jammer is activated, the effect on the already weak signal is obvious, as the mode of the device broadcast completely overrides the signal

Now, the only thing to do is to examine its internal components and understand its functionality. Given the low price, it's still amazing to see how something so cheap can cause such significant damage.

On one side of the PCB, we can only identify two key components, the 78M05 regulator that reduces the vehicle's 12-volt power supply to 5 volts, and the infamous NE555 timer known to hackers. Unfortunately, it took the removal of illegal jammers to finally discover one of the most iconic integrated circuits in the history of electronics, but that's the reality.

Radio frequency in vessel

There is no doubt that the component labeled 13BA A041 is the main attraction. So, what is it? Although I was unable to find a datasheet for that particular model, it has been identified as a microwave voltage controlled oscillator (VCO). The metal top we see is actually a shielding material, and with some effort we can examine the surprising array of components crammed into the tiny space of 9mm x 7mm.

The basic working principle of the device is that the control pin of the VCO (identified as VC on the screen) is linked to the output of the 555 timer on the other side of the board. The signal of the 555 timer modulates the output of the VCO, which causes us to observe noise centered on the 1,575 MHz GPS frequency.

By connecting the oscilloscope to the VC pin, we can see the 133 KHz sawtooth signal produced by the 555 timer. Adjusting this signal could change the frequency range in which the jammer operates, but the extent of this possibility is unclear without a VCO data sheet. Since these components are likely to be the cheapest, it is reasonable to assume that the limitations may not be too great.

In addition, it is necessary to study the small four-pin device designated Q6 at the top of the board. When the high frequency signal is passed from the VCO to the center pin of the antenna connector, it is placed directly in the path of the high frequency signal, so it makes sense to use it as an amplifier. However, it can also be used as a diode to protect electronics from anything that might be picked up from the antenna.

What are the frequencies of all GPS signals?

GPS signal frequency band:

GPS L1:1570-1580MHz

GPS L2:1227.60 MHz

GPS L3:1381.05MHz

GPS L4:1379.913 MHz

GPS L5:1176.45MHz

Usually, the civilian frequency band only needs to block GPS L1 L2. Most devices only use GPS L1.