|Instant-on radar can easily clock speeders in less than one second.|
Detector designers walk a tightrope, balancing speedy response
with accuracy. A detector with a hair trigger may be the first to alert, but with
little time to process a signal, it often gets it wrong. The result is a false
But a too-leisurely response also imposes risks. This is
because modern police radar with DSP
(digital signal processing) is commonly
used in instant-on mode to evade detectors. It's kept on standby, not
transmitting a signal. When a target of interest appears, with a button-press
the officer can check its speed and return to standby mode, all in less than
An MPH Industries radar used in POP mode
is even quicker,
accomplishing this in less than 0.07 second. By design, target speeds in POP
mode can't be locked and MPH wisely cautions officers against taking enforcement
action based on these snapshots.
That's because there's no time to establish a target's tracking
history, required by radar case law to help reduce incorrect target
identification—and bad tickets. Tracking history in moving mode
and target both rolling—has more importance.
variables, particularly when traffic is heavy, increase the possibility that the
officer unknowingly is eying a vehicle different than the one producing his radar's
Trouble is, lazy officers tend to skip the tracking history.
Many trigger the radar, glance at the speed, then return to standby mode. Many also shut off the radar's audio Doppler,
a vital tool to make certain that both radar and officer are looking at the
same vehicle. Officers like this are the
ones you'll want to avoid.
Most detector manufacturers have slowed response to cut
false alarms, likewise making POP mode a user-selectable menu option. I
wondered how many instant-on radar signals are being missed as a result.
To find out, I gathered up six detectors from four
manufacturers. All were tested in Highway mode in their default settings.
Two radars were used: a Stalker Dual Ka-band and a Decatur
Genesis II K-band radar, both operated in stationary mode. With a stopwatch and
using the instant-on remote control, I first established the minimum signal
duration each detector required before it would process a signal and sound an alert
With that baseline established, I repeated the test 20 times
for each detector on each band. The
average of each set was then calculated.
Quickest of the group was the Whistler CR75; it alerted reliably
to K-band radar signals of 0.35 second duration and Ka-band signals at least
0.41 second long. The Cobra SPX 6700 was almost as fast.
The second-quickest in response was the Escort RedlineXR
0.45 and 0.52 second, on K and Ka, respectively. (A standard Redline takes
twice that long to respond to either band.)
The Escort Passport Max
ignored K-band signals that lasted
an average of less than 1.42 seconds. It was faster on Ka band though, alerting
to signals averaging 0.68 second in duration.
BEL and Escort have a feature called TSR, designed to counter
K-band nuisance signals. Many are caused by traffic flow-sensing radar
increasingly being found along major highways. These cause a K-band alert every
mile or so, a phenomenon mentioned in a previous post.
Whistler has similar technology, called TFSR, for the same
purpose. Cobra has yet to join them and we noted frequent alerts to our local
Traffic Flow Sensing radars as a consequence.
We've tested both TSR and TFSR and find each an effective
way to quell false alarms generated by the traffic-flow radar. But there's no
free lunch: engaging TSR or TFSR significantly slows response times as the
microprocessor pauses to evaluate suspect K-band signals.
This accounts for the dramatic disparities between BEL,
Escort and Whistler detectors in K-band response. Whistlers with TFSR—including
models CR70, CR75, CR85
—all ship with TFSR turned off. In contrast,
all BEL and Escorts come with TSR turned on.
To quantify the effect, when we turned off TSR the Escort Max would
alert to K-band radar signals that averaged only 0.32 second in duration. With TSR
on it took 1.42 seconds. Other BELs and Escorts—except the Escort RedlineXR—acted similarly.
The jury's out on which strategy better protects against K
band. In default mode, TSR's leisurely response means BEL and Escort detectors
are likely to miss some instant-on radar signals. On the upside, they will bark
fewer K-band false alarms.
The Whistler handles the TFSR on-or-off dilemma by giving
only a single beep in reaction to brief K-band signals. (It does the same on Ka
band.) If K-band alerts still prove troublesome, a user can activate TFSR, a
10-second task. Now it will ignore K-band signals lasting less than one second.
In the end, user experience will dictate whether TSR or TFSR
will be used. Drivers not plagued by traffic flow radar won't need these
features and can benefit from quicker K-band response. For everyone else:
expect less protection from instant-on radar.