Searching for interesting electronic devices on eBay often leads to suggestions for questionable gadgets. Recently, I stumbled upon these tiny GPS jammers that plug directly into an automotive 12V outlet. Shipped to your door for under $10 USD, it seemed like the perfect device to experiment with, in the name of science. Now, you might be wondering what legitimate uses such a device might have. Well, as far as I’m aware, there aren’t any. The only reason you’d want to jam GPS signals in and around a vehicle is if you’re trying to get away with something you shouldn’t be doing. Maybe you’re out driving a tracked company car and want to enjoy a quick two-hour nap in a parking lot, or perhaps you’re looking to disable the integrated GPS on the car you just stole long enough for you to take it to the chop shop. You know, as one does. But we won’t dwell on the potentially nefarious reasons that this device exists.

Eager to explore the boundaries of technology, hackers have always embraced a wide range of devices for their investigations and experiments. Without discrimination, they dive into the unknown, seeking to understand the inner workings of each piece of hardware. Today, we join them in this quest, venturing into the gray areas with a particular device. Let’s see what makes it tick and what secrets it holds.

• Can You Hear Me? Signal Jammer
• Betrayed: Can You Trust Your Oldest Friend?
• RF Magic: Jamming Signals in a Can?
• Surprise Turned Sour: What Happened?

Can You Hear Me? Signal Jammer

The fragility of GPS signals, with their low power and weak reception, actually makes low-cost signal jammers possible. GPS satellites orbit at an average altitude of 20,200 kilometers, which is quite far away, resulting in a very weak received signal that is generally below the noise floor. Despite this incredible distance, and given the small size of antennas on most GPS-equipped devices, it’s remarkable that we can receive any signal at all. However, this weakness allows simple jammers to easily overpower the legitimate GPS signal. These jammers don’t mimic a GPS satellite, but instead broadcast enough loud nonsense that the real satellite can no longer be heard. Clever algorithms and a bit of wizardry are needed to turn these whispers from the stars into useful information on your phone.

The legitimate signal, originating from tens of thousands of kilometers away, stands no chance against the powerful broadcast of the jammer. As the device screams its head off at arm’s reach, the already meager signal is completely obliterated by its patterns. I didn’t prolong the test to determine the jammer’s precise range, but it’s evident that it can effectively disrupt signals at several meters, if not more.

Betrayed: Can You Trust Your Oldest Friend?

Operating this device for just a few minutes confirmed its advertised capability, albeit illegally. Upon tearing it down, we discovered how it works with such simplicity, yet causing significant disruption. Inside, for the mere $8 spent, lies a 78M05 regulator, converting the vehicle’s 12 volts to 5 volts, and the infamous NE555 timer. It’s remarkable to see this iconic IC from the electronics history in an illegal jammer. However, unless targeting AM radios, the 555 alone won’t suffice. Turning the PCB over reveals the main culprit behind the chaos.

RF Magic: Jamming Signals in a Can?

Looking at the compact and powerful 13BA A041 component, it’s evident that we’re dealing with a microwave voltage-controlled oscillator (VCO). While specific datasheet details for this model remain elusive, its intricate design reveals an impressive array of components packed tightly within a mere 9 mm x 7 mm space. Delving deeper, we find that the VCO’s control pin, marked as VC on its surface, is cleverly linked to the output of a 555 timer situated on the board’s opposite side. This clever configuration allows the signal from the 555 to modulate the VCO’s output, ultimately generating the distinct noise centered around the 1,575 MHz GPS frequency. The metallic shield, visible as the top plate, protects this intricate circuitry, ensuring optimal performance even in demanding environments.

Examining the inner workings of a signal jammer reveals several key components at play. Notably, the 555 timer produces a 133 KHz sawtooth signal, visible with a scope connected to the VC pin. This signal is adjustable, potentially shifting the jammer’s operational frequency range. However, without a datasheet for the VCO, it’s hard to determine the exact limits of this adjustment. Given the presumed use of cost-effective components, the range may not be extensive. Another component worth noting is the small four-pin device labeled Q6, situated at the board’s top. Its location in the high-frequency signal path, between the VCO and the antenna connector’s center pin, suggests a strategic role. This could be an amplifier, boosting the signal strength, or possibly a diode, offering protection to the electronics from any incoming signals picked up by the antenna. Each component serves a crucial function, contributing to the overall performance and capabilities of the signal jammer.

Surprise Turned Sour: What Happened?

Exceeding all expectations, a cheaply imported Mini GPS Jammer from eBay proved to be highly effective, despite initial doubts. Its ease of accessibility and use poses significant risks, especially in the wrong hands. Although information on building such devices has been publicly available for years, sourcing parts and assembly were previously obstacles. Now, with the low barrier to entry, this technology’s potential for misuse is alarmingly high. While WiFi or cellular jammers pose an immediate threat, the proliferation of GPS jammers is equally concerning. This device’s effectiveness and affordability make it a dangerous tool that could be easily abused.