Mike Valentine
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Radar Detector Technology - GPS Blocking

GPS fails the Murphy's Law test
That's why we don't use GPS to block unwanted signals. I tinkered with the idea nearly two decades ago but could never design a detector that could pass the Murphy's Law test. Turns out, neither can the several other detector makers who've offered GPS detectors since.

Here's why: Because there's no difference between the signals we call "false alarms" and those of real radar, every blocking system blocks real radar just as eagerly as it does the unwanted alerts.

The Federal Communications Commission lumps traffic radar into the same X and K band frequencies that it assigns to store door openers, microwave intrusion alarms, and other common devices. So, to a radar detector, all of these signals look the same.

"I see nothing"
Since the signals are indistinguishable,the GPS method uses a simple work around. In effect, it shuts its eyes to a section of the radar bandwidth. Here's how: it divides the bands into channels. Think of a board floor. Each board represents a channel. Imagine dropping a coffee bean on that floor, the equivalent of a microwave signal somewhere in the band. The idea behind GPS blocking is this: the detector knows the car's location when it picks up the signal, and it knows what channel the signal fell into so, by blocking that channel whenever the car is in the marked location, the unwanted signal should be gone forever.

Real radar in a blocked channel
But here's the problem. If you drop a second coffee bean on the floor, it might fall on the same board. With a GPS detector, you are betting that any radar operating near a blocked alarm will be in a different channel. But remember Murphy's Law. If it's possible for radar to be on the same channel, it will be there some of the time.

Another problem: the transmitters used to open store doors are cheap, non-precision devices good enough to "see" something near the door, but they aren't engineered to keep a stable frequency. So the frequency drifts as temperatures change, which means they can move out of their GPS channel. When that happens, they're false alarms again.

When a GPS-detector user goes through a location he's blocked once before, and hears the unwanted alarm again, he blocks it again. But now he's got two adjacent channels blocked and the chance of a Murphy's Law failure is much, much greater.

GPS can't block moving alarms
Murphy's Law isn't the only problem with GPS blocking. Remember that a GPS detector marks and remembers fixed points on earth. But a significant number of K-band falses are caused by leaking local-oscillator transmissions from other radar detectors. Since they're on the move, GPS has no chance of blocking them.

Finally, a better idea
Instead of GPS, we have a better way of minimizing unthreatening alarms, a way that eliminates Murphy's Law failures. It's called SAVVY®, a small module that plugs into the onboard diagnostic port on any car built since January, 1996. That port provides power (12 volts) and streams vehicle-speed data. You plug V1's power cord into SAVVY. Using SAVVY's thumbwheel, marked in mph from 15 to 65, you set a speed threshold. Above your set point, V1 sounds at its normal volume. Below, it sounds at its muted volume; adjust this with the control lever.

A partial list of devices operating on X- and K-band under 47 CFR Part 15.245 regulations as “field disturbance sensors.”
Motion sensors for operating automatic doors (used in malls, offices and industry).
Motion sensors for detecting intruders, used both indoors and outdoors.
Motion sensors for detecting room occupancy for energy management of lighting and HVAC.
Speed sensors for sports radars.
Speed sensors for agricultural vehicles.
Speed sensors for railroad vehicles and track surveillance.
Motion and speed sensors for golf training (speed of ball and motion of club).
Speed sensors for traffic measurement and monitoring.

Motion sensing toilet

Kohler, the upscale maker of bathroom fixtures, has recently introduced a toilet that sees you coming and prepares for your needs. For females, Numi lifts the lid; for stand-up males it lifts the seat, too. How does it know? Radar senses the position of approaching toes.

Kinda nifty. But when radar is on duty in your bathroom, you know it's everywhere around you. Trying to block it, at the cost of giving up a slice of your detector's coverage, is a losing proposition. Because the "give ups" will become more and more as radar inevitably proliferates.

SAVVY is automatic
Instead of blocking alarms, some of which might be radar, SAVVY automatically turns down the warning volume at speeds below your set point. In metro driving and particularly in neighborhoods with big-box stores, SAVVY drops the sound to an undistracting level while preserving the Flow of Information from V1's arrows and bogey counter.

Speed sensors for local traffic (trailers showing "Your Speed Is….")
Anti-collision sensors for industrial cranes.
Vehicle lane-change warning systems used by Audi, VW, Chrysler, and perhaps others.
Tracking systems for smart traffic-control signals.
Sensors for environmental measurement—ice and rain detection.
Tracking systems for industrial process control.
Vehicle security alarms used in some Toyota and other models.

See FCC 47 CFR Part 15.245 regulations for the complete list.

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