file.newsgroup.cars.103742 Maven / Gradle / Ivy
From: [email protected] (David Hwang)
Subject: Re: Best Radar Detector - VALENTINE-1?
In article <[email protected]> [email protected] (Troy Wecker) writes:
>
>Let me explain why I feel the "bogey" counter feature is a gimmick.
>Radar waves bounce off objects especially metal. That is how radar
>speed measurement works. A high frequency microwave (X band approx 10
>GHz and K is approx 24 GHz) is sent out and reflected back to the
>antenna off of an automobile or other objects. If an object is moving
>a Doppler shift (about 34 Hz per MPH on X Band) occurs, is measured
>and converted to miles per hour. These waves bounce all over the
>place and they can reflect many times and go in many directions.
>
>From what I understand the Valentine-1 can only tell if these
>microwaves are coming from the front, rear or both. There are only
>two antennas. If they are coming from both this in interpreted as a
>"side bogey". Bogey counts are determined as sources by their
>relative strength to one another even if they are reflections of the
>same source.
>
I'm certainly no engineer and really have no scientific basis
on which to make this argument, but don't you answer your own
question? Is the reflected signal "shifted" at all from the
act of being reflected? If so, wouldn't it then be easy for
the detector to discriminate between reflections and direct
sources?
>Here is the problem. Since the microwaves reflect, how does the unit
>tell if it is a "source" or a "reflection"? Take a Valentine-1 and
>drive to the local grocery store that uses an X-Band radar door
>opener. You can tell by the small black box above the door pointed
>down at about a 45 degree angle and your detector going off when it
>gets near. The Valentine-1 will count 7 or 8 bogeys from all
>directions front, rear and sides (it doesn't say which side). The
>count changes as cars drive by and reflections change. Is there 7 or
>8 sources? Not at the store I go to. As I drive around with a
>standard detector I can only find one source and that is the door
>opener for the front door.
>
>Troy Wecker
>[email protected]
>Sequent Computer Systems
>Beaverton, OR
--
David W. Hwang, M.D. [[email protected]]