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GPS Jamming: Two Tools to Identify the Source

Franck Boynton, VP and CTO, NavtechGPS
February 12, 2018

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In December, I highlighted the potential threat of GPS interference, jammers and spoofing to businesses. Let’s take a deeper look at a couple of tools on the market from the UK company Chronos Technology to help protect your company from harm.

The Chronos Technology CTL3520 Directional Handheld Jamming Detector and Locator is a battery-operated device designed to detect and rapidly locate the presence of jamming and interference signals from commercially available GPS jammers, as well as identify excessive power or interference broadcast in the GPS (L1) band.

I’ve been fortunate enough to have used the CTL3520 to help some of our customers locate unintentional jamming in multiple locations. The causes of unintentional jamming can include:

  • GPS receiver with a short in its antenna
  • Radio frequency (RF) section that is erroneously transmitting on GPS frequency
  • Bad amplifier on a PA system
  • Wireless microphone transmitters
  • Surveillance cameras which didn’t have an RF output
  • Improperly terminated RF output

I always carry the CTL3520

Given my field of work, I always carry the CTL3520 in my tool box — first, to be sure that I don’t personally cause interference, and second, and more importantly, to make sure there isn’t anything interfering with a system that I install for a client.

The first time I used the CTL3520, I was invited by our customer, along with two other experts who had omnidirectional spectrum analyzers, to identify the source of GPS interference to the customer’s equipment. The spectrum analyzers were able to detect the interference and show it was at a high gain, centered at 1575 MHz in strength, but were unable to pinpoint the source and location of the interference quickly. The equipment the other experts used was very heavy, bulky, expensive and took considerable training to operate.

I pulled out the CTL3520 and pointed it in an arbitrary direction and saw no indication on the LCD or the LEDs. I turned 180 degrees, and it hit hard immediately, and nearly off the scale. I followed the signal while attenuating the input of the CTL3520 and found, above a wall about 30 feet away, a small omnidirectional whip antenna. When the amplifier attached to the antenna was powered off, the jamming signal immediately died.

While I was there, we took advantage of my CTL3520 to locate other sources of interference on the property. The customer decided to purchase a unit right then and there to clear the rest of their property. The CTL3520 was powerful, easy to use, fast, accurate and cost-effective. I really never do field work without it.

Another valuable tool for detection and data logging: CTL3510 LOG

Another valuable tool from Chronos Technology is the CTL3510LOG GPS Jammer Detector, with built-in logging. This tool not only detects the presence of GPS jammers, it can log months of data for later analysis with its included software. This is especially useful for detecting GPS jammers hidden in work vehicles — one of the more common abuses of jammers by individuals who want to defeat a company’s fleet tracking system when they “deviate” from assigned routes.

The CTL3510LOG comes with software to filter searches, to filter the jamming duration through its time stamp, and just as importantly, to measure the strength of the jamming. If the jamming is brief and low gain, the interference is probably from an outside source, such as a vehicle containing a jammer that drove near the vehicle in question and then drove off.

If the tool indicates strong, consistent jamming, at a consistent level and for a long period, it is a good indication that the jamming is within the target vehicle. The CTL3510 can be placed in a vehicle, eliminating the need for a supervisor/manager in the field to track down the source of the possible violation. Once it has been determined that jamming is occurring in a company- or city-owned vehicle, you can deploy someone in the field with a directional CTL3520 and catch the jamming in the act. This two-prong approach substantiates the violation so further action can be taken.

These tools make it very difficult for the person driving the target vehicle to use a jammer without getting caught by management, and they help management target the right subject and avoid blaming the wrong person or source for the interference.

There are many business applications that could take advantage of GPS jammer detectors and locators like these. We can help you with strategies for how to best use these devices to achieve your goals. NavtechGPS is the North American distributor of the entire line of Chronos Technology CTL jamming detectors.

Food for Thought: As of the writing of this article, there were no U.S. companies that manufacture GPS jamming or spoofing detection tools. Why do you think this is? Why aren’t more U.S.-based companies interested in this technology?

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