Discussion About Radar Detectors

[2WheelTiger]

One of the biggest "transmitters" in the average house is a CRT monitor. It's actually quite easy to synchronize a receiver to the refresh rate of a monitor and (quite literally) read what ever is on the screen.

However, one cannot say that these monitors "deliberately" emit a signal.

 

[ponyfool]

Would you think that a GPS speed reading is more, or at least, AS accurate as speed measured by a radar gun that's been calibrated? The speedometer in my truck runs about 4 1/2 mph slower than what my GPS indicates.

Radar and LIDAR speed readings are not very accurate at all in real world uses. The cosine effect makes the Radar or LIDAR's reading to be lower than the vehicle's actual speed. The only time Radar and LIDAR speed readings are 100% of the actual speed is when the object being read is coming directly at the unit with no offset angle. Since most uses of police Radar and LIDAR are when the officer is off to the side or at an elevation, the speed error is always in favor of the driver.

Now, having said that, my only experience with GPS speed is from a unit that only took a measurement every minute or two, thus the speed reading would only be an average speed between readings and not actual speed.

I don't know how frequently current GPS models take their readings, but unless it is really frequent, it still will only reflect an average speed rather than actual speed. But, with technology advancing, it wouldn't surprise me if GPS units were taking a reading every few seconds or so. Get one that reads a few times a second, and you'll have about as accurate a reading as you can find....if the unit is working properly.

 

[Powerman]

I'm an electronics guy in a detector banned state of Virginia, I've been thinking alot about this lately.

It would seem that the manufactures would shield or block the local ocsillator signal if they could?

The ones I've peeled open had shielding around the circuit board. When my radar expert gets back from vacation, I will run it past him.

 

[brazos parker]

First off, mark me up as one of those guys that believe radar detectors offer only marginal protection against a well-trained LEO w/ instant on RADAR/LIDAR. Especially against a "speeder" running alone w/out a "rabbit" out in front.

Having said that, I find this discussion verrrry interesting. However, I'm not an electronics techno-guy, so pls excuse the following...

With no radar signal coming down the hill towards the car, the radar detector sees the radar waves going over the hill into space and gives an advanced warning.

Can someone pls explain the above quote? The RD "sees" the transmitted radar waves shooting out into space from over the hill...w/ no reflections? Huh? and, How?

Sorry if this is a dumb question but it's curious to me how the RD "sees" the waves.

 

[BobG]

I would love to hear the answer to that too.

Also

If you have a radar that is reading the LO of a device, how do you know what electronic device is transmitting it, IE false readings?

Being that there are trans/receivers all over the place used by just about all the Agencies, and public service I know of.

As for for fooling a radar gun or laser gun it can be done. But it takes money I don't have.

Things can be rendered invisible to electronic signals.

Bob

 

[Orient_Express]

First off, mark me up as one of those guys that believe radar detectors offer only marginal protection against a well-trained LEO w/ instant on RADAR/LIDAR. Especially against a "speeder" running alone w/out a "rabbit" out in front.
Having said that, I find this discussion verrrry interesting. However, I'm not an electronics techno-guy, so pls excuse the following...

With no radar signal coming down the hill towards the car, the radar detector sees the radar waves going over the hill into space and gives an advanced warning.

Can someone pls explain the above quote? The RD "sees" the transmitted radar waves shooting out into space from over the hill...w/ no reflections? Huh? and, How?

Sorry if this is a dumb question but it's curious to me how the RD "sees" the waves.

I agree - I don't think radar detectors give you a big edge - although there would be many who would say one saved them from a citation.

All radio waves are subject to reflections. We've chased spurious transmissions that cause degredation to our TVRO earth station sites from RF signals reflected off billboard signs, buildings, etc. Reflections also make signal leakage seem to come from one direction, while the actual source comes from 180 degrees. As signals are transmitted (even microwave - which is almost a thing of the past) they start to fan out over distance. AM & FM broadcast stations (Rock 103 or TV) intentionally broadcast using a multi-directional antenna to cover large listening / viewing areas. I believe radar like microwave uses a mono-directional antenna - i.e. narrow beam with little side lobe transmission sending a frequency modulated CW carrier. However, there is still scattering of the transmitted signal over distance - like a shotgun pattern. The detector receives a portion of the fanned out, scattered or reflected signal, while "over the hill" or at a distance and gives you "advanced warning".

Some years ago when I was into amateur radio, there was a long distance communications technique called Tropospheric Scatter. A high level, microwave signal that was frequency modulated was transmitted towards the sky at a specific angle. Most of the signal went on to Jupiter, but some was bounced off of the troposphere and came back to earth, but in no real accurate direction or pattern. (Much the way satellite signlas are received today) The received signal was weak, but still usable. Of course a number of things like weather, played havoc with the technique since at the receive site, the level had been diminished considerably. This is similar to how a radar detector is supposed to give advanced warning, although the LEO is not aiming for the sky.

My question about GPS speed comes from the refresh rate of the receiver - which, I beleive is about 1/sec on most brands - models. That would seem to be very accurate to me... Anyone know???

 

[Orient_Express]

I would love to hear the answer to that too.
Also

If you have a radar that is reading the LO of a device, how do you know what electronic device is transmitting it, IE false readings?

Being that there are trans/receivers all over the place used by just about all the Agencies, and public service I know of.

As for for fooling a radar gun or laser gun it can be done. But it takes money I don't have.

Things can be rendered invisible to electronic signals.

Bob

Whoa - there's a thought - what local oscillator is the radar gun reading and is it even coming from a vehicle?? Are they that frequency selective?? If so, that's pretty narrow band and must cost big bucks.

Dang BobG - that's a darn good question?? Are there diff LO signatures based on model / brand of detectors.

What a can of worms... I still can't get over those things transmitting a signal... :blink:

 

[Pjturbo]

Anyone who has run an RD know that it will detect another RD. So at least one of them is emitting. The Valentine even has a special sound for another RD.

Phil

 

[wfooshee]

I used the word "leak" first, and what I meant was probably insufficient shielding. The internal superhet signal is receivable outside. The device doesn't intentionally transmit, that would require licensing, but it may emit what should be called "noise" which is what detector detectors find them with. The CRT example above is a good comparison. CRTs are very noisy.

There's no 'beam" to intercept an over-the-hill or around-the-corner transmission. They're supposed to work kind of like the way you see the glow of an oncoming car before he crests the hill. That glow is supposed to be visible to good detectors, but passively, not by any signal going out.

My very first (and completely useless) radar detector, some 20 years ago almost, was pre-superhet, and thus not nearly as sensitive or discriminating as modern detectors. It would beep for police radar, maybe, as I was being stopped. It went crazy every grocery store I passed, and warned of nuclear war whenever an F-15 (but no other aircraft) was approaching! The best one I ever had was a remote antenna with a small display in the car. Had that long enough for three cars! When it finally died, I didn't bother replacing it, as I'd found that watching traffic was a better detector than anything electronic I could ever buy.

(How about a scale helicoptor that flies ahead of you with a TV camera, police scanner, and radar detector? Now how about EVERYBODY having one?) :lol:

 

[twodogs]

[
I don't know how frequently current GPS models take their readings, but unless it is really frequent, it still will only reflect an average speed rather than actual speed. But, with technology advancing, it wouldn't surprise me if GPS units were taking a reading every few seconds or so. Get one that reads a few times a second, and you'll have about as accurate a reading as you can find....if the unit is working properly.

My Garmin (26something) updates about every second so I presume it measures about that often as well.

Bill

 

[nmanley]

[
I don't know how frequently current GPS models take their readings, but unless it is really frequent, it still will only reflect an average speed rather than actual speed. But, with technology advancing, it wouldn't surprise me if GPS units were taking a reading every few seconds or so. Get one that reads a few times a second, and you'll have about as accurate a reading as you can find....if the unit is working properly.

My Garmin (26something) updates about every second so I presume it measures about that often as well.

Bill

The GPS units calculate most all of their calculations in Milli seconds but only update the screen about once a second which is about as often as the human brain can absorb and rationalize. It's also plenty of time to realize if your speeding or not.

 

[Last Chance]

Theory? - Hardly. In answer to your post - they are called "detectors" because they "detect" (receive) a signal that's been transmitted. If they transmitted a signal - they would be labeled as transmitters. If they transmit & receive - transceivers.

I can get into a pissing contest with you if you'd like, but if you would have read ALL of the web page you copied and pasted here, you would have seen this too:

Detecting DetectorsSince they have an oscillating current, all radio receivers not only pick up radio signals, they also emit them. This means that any radar detector, whether it has a jammer or not, broadcasts a tell-tale radio wave whenever it is turned on.

In areas where radar detectors are illegal, police may be equipped with a device called VG2. The VG2 instrument is simply a high-powered radio receiver tuned to the frequency of the signals emitted by radar detectors. So while you're scanning the area for them, they might very well be scanning the area for you.

I have been using police radar for 18 years. Lidar for 11. I have been to countless classes, and have learned about the units we use as well as radar detectors. When I was an officer in Virginia, I was one of the first people to use the radar detector detector. In that class, I was specifically taught how the unit worked to detect radar detectors, and what I explained in my previous post is accurate. A radar detector transmits a signal and is NOT receive only as you and your quoted web page suggest.

Interesting question. Does a radar "detector" "transmit" a signal. Yes and no. The oscillating current referred to above is part of the "receiver" circuitry. A radar detector is really only a r/f receiver like any other receiver. It only receives at a much higher frequency than say the commercial broadcast band. Specific circuitry has been developed over the years to improve the "selectivity" and "sensitivity" of radio receivers. Example: the "superheterodyne" receiver. These circuits utilize an oscillator circuit (often consisting of a quartz crystal) as a means of "filtering" the received signal and eliminating unwanted signals (noise). The radar detector, detector is itself a radio receiver, designed to receive the frequencies utilized by the radar detector's oscillating circuitry.

So, in a sense you are both right.

I, however, as a licensed ham operator am entitled to build and operate equipment in certain radio spectrum bands. I know of hams operating "transceivers" in the "X" band perfectly legally. I've often thought of checking to see if our "ham bands" have a band near the K, Ka radar band. Perhaps building a K, Ka band transceiver, mounted on my motorcycle would be a worthwhile project.. I could then go around transmitting CQ de: K7LC all over the countryside, looking for a fellow amateur operator to "talk to". Of course I might only "listen" for a response when stopped for meals or fuel.

LC

 

[Orient_Express]

I, however, as a licensed ham operator am entitled to build and operate equipment in certain radio spectrum bands. I know of hams operating "transceivers" in the "X" band perfectly legally. I've often thought of checking to see if our "ham bands" have a band near the K, Ka radar band. Perhaps building a K, Ka band transceiver, mounted on my motorcycle would be a worthwhile project.. I could then go around transmitting CQ de: K7LC all over the countryside, looking for a fellow amateur operator to "talk to". Of course I might only "listen" for a response when stopped for meals or fuel.
LC

LC - I have worked with several hams in quelling signal leakage as it gives them fits - especially anything above 100uV/m. I too was a ham some time ago (when they used to give the code test to get your first license) and wish I'd stayed with it.

That is an interesting idea - building a K band transceiver and running a repeater with a transmit every so often - say once every 3 seconds. If there is an amateur radio band there, it wouldn't take too much power to give a radar gun fits...

Do you know if that could be considered "jamming" as it is a transceiver and you are operating legally?

 

[Last Chance]

I, however, as a licensed ham operator am entitled to build and operate equipment in certain radio spectrum bands. I know of hams operating "transceivers" in the "X" band perfectly legally. I've often thought of checking to see if our "ham bands" have a band near the K, Ka radar band. Perhaps building a K, Ka band transceiver, mounted on my motorcycle would be a worthwhile project.. I could then go around transmitting CQ de: K7LC all over the countryside, looking for a fellow amateur operator to "talk to". Of course I might only "listen" for a response when stopped for meals or fuel.
LC

LC - I have worked with several hams in quelling signal leakage as it gives them fits - especially anything above 100uV/m. I too was a ham some time ago (when they used to give the code test to get your first license) and wish I'd stayed with it.

That is an interesting idea - building a K band transceiver and running a repeater with a transmit every so often - say once every 3 seconds. If there is an amateur radio band there, it wouldn't take too much power to give a radar gun fits...

Do you know if that could be considered "jamming" as it is a transceiver and you are operating legally?

I guess this is why we have lawyers. I would have to research the band allocation to see if:

1. Is there "joint" use of the band by police radar and hams?

2. If not is the ham band allocation close to or a multiple of the radar band?

3 If is were close to the police radar allocation, then "poor shielding" or a slightly "sloppy" signal might "overlap", (unintended, of course) interfering with the police radar reception.

4. If the police "share" the band with hams, then no problem. I'm just utilizing my amateur privileges.

I would think one could go to court, if challenged, and as long as one were properly licensed one would at least have a "plausible" defense. If the band is "shared" then all users have to "accept" the limitations by such sharing. However, on some bands, if hams "interfere" with a higher priority user, the ham must discontinue transmitting when it interferes. When would that be? And how is the ham to "know" when he is interfering? Once set up, I would be more than happy to cease transmitting if notified by a LEO that I was "interfering" with his use of the band. :yahoo:

I know some hams build transceivers in the high gigahertz frequencies and actually try to make contact with each other from mountain tops etc. I prefer the low bands and CW myself so I have never "experimented" with the equipment. I'm also lazy and have too many "hobbies" as it is. It would be fun though.

Since Escort makes a "shifter", a transmitter to shift and "rebroadcast" the LIDAR signal, it must be "legal" to do so. Or, at least not "tested" in court yet.

It would be fun to play around with it though. Not to mention the satisfaction I would get frustrating the LEO's. After all, they have been frustrating me for 40 years and I have PAID my dues! (Considering the milage I rack up, I have a very good traffic record.)

I try to keep below the RADAR, pun intended. I also consider using powers of observation and risk management to be more important in avoiding citations than technical devices. CB being the exception. But who can stand to listen to that all day, I know I can't.

LC

 

[Orient_Express]

A "code" guy huh??

Interesting - Those are excellent points - the FCC uses the same language on interfering signals for signal leakage but never sets a measurement as a point of interference - that could be anything!!!

There's a spurious signal we test for during FCC proofs called CSO or Composite Second Order.

It's a distorsion product - a beat that shows up at .75 and 1.25MGHz above and below the CF of a video carrier. You can have all four beats show up - basically killing picture quality as it messes with the video. You'd never know they were there when the channel is being modulated and can't see them until the modulation is turned off. It's caused by the high level of transmission of two analog video carriers that form a beat product by adding or subtracting in frequency. I made a training setup for new Maintenance Techs by using two modulators and watching the beats "appear" on a spectrum analyzer above and below the center freq of a totally diff channel - it always gets a wow out of new guys.

This isn't a "shift" any frequencies by a few KHz - but the beats can be pretty high in level. I've seen them as high

as -25db/uV with a CF carrier of a channel at +10db/uV. Normally they test out at -60 to -70db/uV, so -25 is very high and will not pass the proof test.

Winegaurd made a small pre-amp a few years ago for Winnebago that was supposed to improve analog television reception. Our Construction Manager, who's also a ham lives close to one of those RV parks and said the darn things were shielded so poorly that they were causing havoc even with his digital channel reception. Winnebago did a recall on them - you might see if you could find one of those babys - don't know exactly what freq range they mess with, but can ask if you want me to.

I've never heard of the Escort "shifter" - that's sounds like something to play with!!

 

[Last Chance]

A "code" guy huh??Interesting - Those are excellent points - the FCC uses the same language on interfering signals for signal leakage but never sets a measurement as a point of interference - that could be anything!!!

There's a spurious signal we test for during FCC proofs called CSO or Composite Second Order.

It's a distorsion product - a beat that shows up at .75 and 1.25MGHz above and below the CF of a video carrier. You can have all four beats show up - basically killing picture quality as it messes with the video. You'd never know they were there when the channel is being modulated and can't see them until the modulation is turned off. It's caused by the high level of transmission of two analog video carriers that form a beat product by adding or subtracting in frequency. I made a training setup for new Maintenance Techs by using two modulators and watching the beats "appear" on a spectrum analyzer above and below the center freq of a totally diff channel - it always gets a wow out of new guys.

This isn't a "shift" any frequencies by a few KHz - but the beats can be pretty high in level. I've seen them as high

as -25db/uV with a CF carrier of a channel at +10db/uV. Normally they test out at -60 to -70db/uV, so -25 is very high and will not pass the proof test.

Winegaurd made a small pre-amp a few years ago for Winnebago that was supposed to improve analog television reception. Our Construction Manager, who's also a ham lives close to one of those RV parks and said the darn things were shielded so poorly that they were causing havoc even with his digital channel reception. Winnebago did a recall on them - you might see if you could find one of those babys - don't know exactly what freq range they mess with, but can ask if you want me to.

I've never heard of the Escort "shifter" - that's sounds like something to play with!!

I'm too lazy and technically incompetent. Sounds like you are the one to run with this one. As to the Escort "shifter", it is a laser countermeasure. Uses multiple sensors placed near the most likely "aiming" points on your vehicle. License plate, headlights etc. Then retransmits the infra red light beam at a different fixed frequency, confusing the LIDAR unit, I assume. The problem is the LIDAR beam is so narrow. I got a brochure with my new Escort RD. $2,000 +! Gotta love free enterprise.

I'll have to tell the story of how I "beat" a 110 in a 65 zone using my "Get out of Jail Free Card". There is such a thing as "professional courtesy". It is not absolute, but in this case the CHP officer was as much a part of the problem as I was, so he extended "professional courtesy" to me because my son is a Federal LEO. Much better than a RD. But, I will not push my luck. I am and will continue to be much more careful in the future, especially at night! Even if I think I'm being pursued by a crazed motorist intent on killing me. Opps, I just did tell the story.

LC

 

[Charlie Hoss]

When ponyfool is "firing" his radar up a hill, MOST of it goes straight into space...but not ALL of it. Radar waves reflect off anything and everything, trees, buildings, bridges, other vehicles, water molecules in the air and probably air molecules. These reflected signals are strong enough to set off the detector but not strong enough to get back to the radar gun. This reflection is the reason a "good" detector will alert around corners and over hills. A good detector will easily pick up a radar signal from behind, even if it is not equipped with a rear facing antenna (like the V1), because of reflected signals.

I read a test a few years ago in which a VG2 detector detector picked up a Passport at over 700 ft, and the V1 was detectable in under 4 feet. Its all in the filtering of the superhet signal. Today, there are more advanced RDDs like the VG4 and the Sceptre which will easily detect any RD with the exception of the Beltronics STi Driver, as someone mentioned earlier in this discussion.

Good topic.

 

[Orient_Express]

I'm too lazy and technically incompetent. Sounds like you are the one to run with this one.
LC

Yesh - Right!!! I'm no engineer - though I do play one on TV...

Here's what our Construction Manager says...

All modes and licensees (except Novice) are authorized on the following bands - FCC Rules Part 97.301(a)

2300-2310 MHz

2390-2450 MHz

3300-3500 MHz

5650-5925 MHz

10.0-10.5 GHz

24.0-24.25 GHz

47.0-47.2 GHz

75.5-81.0 GHz

119.98-120.02 GHz

142-149 GHz

241-250 GHz

All above 300 GHz

Amateur operation at 76-77 GHz has been suspended till the FCC can determine that law enforcement radar systems will not be interfered with

Well - that's the story... So far it would be illegal to do...

 

[BobG]

The impedance of the air is already known, and is calculated into the free space propagation of the initial signal.

It is more the receiver would have to have very high amplification (sensitivity) to read either the the original signal, or reflected signal.

I like the idea of painting the external skin with carbonyl iron ferrite, this decreases the foot print of the bike even more. Oh, paint the helmet with it also.

This only works if you ride alone. If someone is following, they will reflect the Doppler frequency back.

Bob

 

[Orient_Express]

I like the idea of painting the external skin with carbonyl iron ferrite, this decreases the foot print of the bike even more. Oh, paint the helmet with it also.This only works if you ride alone. If someone is following, they will reflect the Doppler frequency back.

Bob

That's good!! One guysomewhere was experimenting with angled panels - Stealth Fighter???

What about an upper sideband trans at... say 76.5???