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"What's New" Reviews
November MT® 2003

Please mention you saw it in Monitoring Times!


K40 RD850 Radar Detector

By Bob Grove


            Radar detectors have become rather commonplace along America’s highways and interstates. The temptation to push the pedal just a little over the posted limits is hard to resist, and any device that will let the driver know that his speed is being monitored is welcome.

            Older radar detectors had their share of problems. Some had enough oscillator radiation to disrupt downlink satellite terminals (VSATs) in the 11.7-12.2 GHz range, such as those used at gas pumps for credit card transactions, Muzak in fast-food establishments, financial transactions and other business applications. As of 2002, these are now illegal to sell.

            Except for commercial vehicles (truckers), radar detectors are legal to use in every state except Virginia and Washington DC. They are illegal to even own, much less operate, in much of Canada! To cope with illegal use of radar detectors, law enforcement agencies employ “radar detector detectors” like the VG-2 Interceptor. These units listen for the weak emanation of oscillator signals from the radar detectors.

            To thwart such detection, some consumer radar detectors are now equipped to listen for the oscillators from the police radar detector detectors! When heard, the radar detector is shut down for a few seconds, allowing the vehicle to drive past the radar detector detector -- without detection!

            Another new technology designed to thwart consumer radar detectors is “instant-on” (“POP”) or pulsed radar, such as the MPH Industries BEE III. This presumes that a speed-measuring pulse can be so short that the detector, which requires at least 150 milliseconds of signal to respond, won’t flash an alert. However, the 67 millisecond pulse is too short for MPH’s own circuitry to stabilize fast enough for an accurate reading that will hold up in court. Therefore, the “POP” must be followed by a longer-duration radar beam which alerts the detector.


K40 Electronics


            K40 rose to prominence in the CB arena some 25 years ago when antenna manufacturers were endlessly beating the drum for their particular products. I had the pleasure of publishing my findings following a field test of the K40 antenna. The bottom line was that it worked well, better than other antennas with which it was compared. It’s still on the market and selling well. Recently, I was given the opportunity to perform a similar test with their new, sophisticated radar detector.


The RD850


            The RD850 comes with a distinguished pedigree, carefully developed to respond quickly and sensitively to all three traffic radar bands: X, K and superwide Ka (33.8, 34.7, 35.5, 24.15, and 10.525 GHz). In addition, the RD850 responds to laser, “POP” (instant-on pulse radar) and VG-2 (11.4-11.6 GHz) radar detector detectors.

            Power is derived from a convenient source of 12 VDC; both a cigarette-lighter cord and direct-connect cable are provided. Audible alert volume is continuously adjustable. The compact, lightweight unit can be mounted with the included sun-visor clip, window suction cup, or dashboard Velcro strips.

            When a target signal is detected, the unit flashes its LEDs and emits a tell-tale tone as well to inform the user of the identification of the signal:  Chirp (K), tweet (X), buzz (Ka), high-pitched beep (laser), or warble (VG-2).


False Alerts


            Occasionally a radar detector will go off for no apparent reason; this is caused by extraneous signals which share the same frequency bands. Such signals include oscillator radiation from neighboring vehicles with radar detectors (the most common), high-power radio transmissions, some cell phones, and other incidental radiators. Parking at or driving alongside shopping centers and industrial complexes affords an excellent opportunity to activate your radar detector! A special filter mode may be selected to reduce, but not totally eliminate, such interference.

            Our older model detector did this frequently as we drove down the interstate and as we stopped at busy complexes. The RD850, however, remained quiet until activated by more legitimate radiators like the occasional stray radiation from other radar detectors employed by passing motorists.


The Lab Tests


            At the request of K40 Electronics, on April 17, 2003, Speed Measurement Laboratories of Ft. Worth, TX  ( conducted an independent, objective evaluation of the RD850 as compared with two other contenders in the field, the Passport 8500 and the Bel 985. Nine of the newest radar and laser guns were operated by a certified traffic officer to eliminate any doubts concerning authenticity of the tests. The 10-year veteran officer was instructed to use the radar guns just as he would in his daily traffic routine.

            The results? To quote SML’s own release, “In our test of the industry’s top rated radar detectors, no other detector outperformed K40’s new portable RD850...”

            Apparently K40 feels pretty confident in their new product as well; they will pay any speeding fines incurred during the first year of the owner’s operation of the device!


On the Road Again


            A 1200 mile trip along I-75 afforded an excellent opportunity to test the new RD850; we decided to try a side-by-side comparison with an older Radio Shack model, each facing out through the windshield of my wife’s new 2003 Jeep Liberty. It didn’t take long for both units to start sounding their alarms. As a matter of fact, all day long they sat there chirping away happily while I visually scanned the horizon unsuccessfully trying to locate the sources of these alerts. False alarms, but from where?

            Finally I had an epiphany: Could the two units be interfering with each other? (Duh...) I switched off the older unit and the falses stopped immediately! This close to each other, the units were hearing each other’s oscillators, just like the radar detector detectors!

            Now quiet, and my wife finally talking to me again, actual radar beams were signaled for great distances. In one case, a low-powered radar speed sign, normally set to alert drivers of their measured speed at a maximum range of 250 feet, triggered the RD850 alarm at 0.8 miles!

            In SML’s tests, the RD850 consistently reported radar in excess of 2 miles from the target -- seven times the normal targeting distance of police radar. At this distance, a vehicle traveling at 60MPH would have approximately two minutes to casually slow down before the typical radar gun could get an accurate reading.*

            The ability to fine-control the audible volume, or instantly mute it, or even replace the various tones with a pleasant Geiger-counter “tick” sound that increases in rate as a radar speed trap is approached, is a welcome touch.

            I was very impressed with the overall performance of the RD850 and feel that it offers a reliable warning well in advance of an activated speed-measurement device.


            The RD850 carries a manufacturer’s suggested retail price of $299.95. For ordering information, visit the K40 web site at, or call (800) 323-6768.


*At 60 MPH (1 mile per minute) it would take 1.75 minutes to get within 0.25 miles; but since the vehicle is gradually slowing down, it allows even more time.


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