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  1. #1

    Default "your speed is".......

    Driving through Connecticut tonight, I hit a turning-on ramp at about 45mph.......much to my surprise, right around the bend was a "stand alone" radar(?) mph booth, listing my speed as 43, 45, 44, 43, 45........

    NOT A PEEP FROM MY RX-65!! :roll:

    what gives?

    I had a Ka hit about 10 minutes earlier, and had several X-band hits by a strip mall 1/2 hour before.

    KA USA
    X on
    K on
    Laser ON
    POP on

    multi threat display, TACH.

    nOTHING!!! :cry:

  2. #2
    Radar Fanatic
    Join Date
    Jan 2005
    East Bay Ca

    Default Re: "your speed is".......

    Do a search for FM-CW for more.....

    "The failure to alert to a particular speed sign might have one of several causes:

    1) The speed sign may employ an FM-CW modulation technique to sense the direction of vehicles in its field of view. This feature is used to isolate departing from oncoming traffic. The V1 does not recognize FM-CW modulation as a valid police radar signal and tries to reject it. FM-CW is allowed for license-free "Part 15" devices by the FCC. FM-CW is not allowed for police radar. There are numerous traffic-volume sensors using FM-CW spread all around metropolitan areas these days that detector owners would rather not produce an alert. Otherwise freeway driving (in Cincinnati, at least) would be very annoying. It's a good thing that the V1 rejects FM-CW modulated signals.

    2) The speed sign may have drifted out of the police radar band from aging or temperature. "Part 15" devices are somewhat notorious for this behavior. Automatic door sensors and Doppler security sensors are both "Part 15" devices, too. Few automatic door sensors use FM-CW because of the added expense. The speed sign devices can afford the added cost of including the FM-CW modulating hardware.

    3) The V1 in question may need for our service department to have a look at it to make sure it is operating correctly."

  3. #3
    Radar Fanatic
    Join Date
    Apr 2005
    Indianapolis, IN


    V1 Dave has a good point. Do the BELs also reject FM-CW radar? Very possibly. It might be a good idea to check with BEL to be sure.


  4. #4


    My work has 2 X-band "Your speed is..." signs which automatically distinguish between and give accurate speed readings for both approaching and going away vehicles... and my Whistler picks them up very strong.

    Though seems like maybe your Bel ignores those types of radar. Write Bel and email and find out.

  5. #5


    Cool, goood info! (as usual....)


  6. #6
    Advanced Member
    Join Date
    May 2006
    Northern Michigan

    Default very correct..

    This is my first conclusion as well...fmcw radar systems... Although do speed signs impliment laser yet?? GOOD ? !!


    Spectre II RDD Tuned by SMS Aulstralia, VG2 RDD, Escort Redline, Valentine One 3.893, Uniden LRD950, Marksman LTI 20-20 Lidar, Ultralyte 100lr lidar,
    Z-25 mph K-band w/pop 16ms.
    Talon Ka 35.5GhzKa, Kustom Pro-1000 K-band w/K55 remote better i/o, (2)K55 X-Band's, TomTom Golive GPS, Laser Interceptor Tri Head, Blinder M-20 Dual head, Cheetah C550 GPS with platinum trinity 3.0 databases, Pro-1000 Wilson Ant, Galaxy 959 W/RF Gain SSB, Uniden 980SSB, (2) pro520xl, (2) Pro510xl cb, BCD436HP Digital/Analog dynamic/Apco 25 Phase I & II capable, Waze via gal s5, GoPro 3+Dashcam, Canon EOS7D, and Panasonic HD camcorders, 1080p watchcam for roadside evidence 16Gb, Lenovo laptop for mobile updating. *Coming soon's (Radenso Se Pro*,Escort Max 360*,ALP, and redline segmentation*)

  7. #7
    Power User
    Join Date
    Feb 2006
    MI / MA

    Default Re: very correct..

    Quote Originally Posted by alpinestars_2002795
    This is my first conclusion as well...fmcw radar systems... Although do speed signs impliment laser yet?? GOOD ? !!


    I've seen a few screenshots/photo evidence of laser-based speed signs.

  8. #8
    Old Timer
    Join Date
    Jul 2005
    Great Lakes

    Default FM

    FM-CW modulation huh. Wow!



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