Radar detectors and harmonic interference

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spymongoose
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Radar detectors and harmonic interference

Post by spymongoose » Thu Jan 06, 2005 9:41 pm

I have always wondered about all the false alarms I get on my radar detector. Most I can isolate to specific areas or sources of radiation (like automatic doors) but there are a lot of other phenomina I wonder about.

Specifically I get interferance from other radar detectors. I was under the impression that radar detectors were passive. Why do detectors interfere with other detectors, regardless of brand or model?

Also I get interfereance from the airfield where I work. The easiest to identify is the one of the radars, operating at 9.0 GHz (x band). Another radar throws my lazer detection alarm into fits, this one I know to be operating in the 2.74 GHz (s band) range. There is also a major TV news doppler radar near where I drive, also setting off my lazer consistantly. Maybe a harmonic?

I use a Valentine One detector, by far the most expensive and sophisticated one I can find, but the other detectors I've owned or the ones in all my friends cars all do the same thing.

Why?
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mratatood
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RADAR DETECTORS

Post by mratatood » Mon Feb 07, 2005 10:06 pm

let me dredge up a bit of my rusty engieering education
radar detectors are just finely tuned recievers. another reciever is powered and tuned to the exact frequency yours is looking for.the other detector is just 'leaking' ,if you will ,the energy that is used to power the oscilator( or phased lock loop (pll)) circuit.
i would be willing to guess that your radar detector picks up cheaper radar detectors from farther away than another good one.

i have an old 80's passport, it seems to work well, and i dont ever think i have gotten a hit off another radar detector. i have a radar "testor" that i use to test the radar detectors on passing cars(it also usually checks their brakelights too :) ) it and mw door openers are the only false hits than i can recall

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Post by spymongoose » Tue Feb 08, 2005 8:04 am

Cool, i belive your right. I was under the misunderstanding that there was some active element in a special grid, but your "simple radio" explanation goes over much better. Some tech-head years ago told me that <cough cough shadowmite> and I bought off on it. The feedhorn internal to detectors must then give it a directional specific sensitivity... and little else. A superhetrodyne radio setup with calculated intermix freq's to give you some of the different bands... I see... wow im a believer. thanks a lot mratatood. Errr, dratatude... :)

If there is some intermediate freq being fed back through antenna, then that leads me to the thought that most radar detectors are poorly engineered devices, or the miniture antenna sucks.

the so called V2 wave, or the radar detector detector signal that the police send out, must be a commonly used intermediate freq used on the first or second stages of the superhet to send back out an amplified responce to the cops.

the valentine one supposedly is immune to that wave. my first thought is that the valentine uses a different first intermediate freq. another thought may be some kid of freq responce limitations on the antenna or freq specific cancelling near the antenna.

as for the intermediate freq leaking out... i have seen speedier people than me slow down due to them picking up interfereance from my detector. hm. oh well. if the folks at valentine havent figgured that out, then i doubt that i can improve on that.
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Post by mratatood » Sat Feb 12, 2005 12:21 am

SPYM
obviously i have not said anything you did not already know. being new to this forum i did not mean to talk down , if it was taken as such , i apologize. i probably could have put it better.

if the source of the interference produces a harmonic (even at a weak multiple)at the radar freqency , the detector is doing it's job by detecting the faintest of signal.
i wonder at the problems they would have with feedback during developement
i think of the tv vans in the uk that would pick up the the scan rastor from tvs that were at addresses that did not have tv licenses and then issueing a citation. or the theory of being able to reproduce a crt disply by monitoring the rf output. i am sure you have heard of this.

have you been happy with the valentine?
i was looking into updating my radar detector and adding laser detection , i have yet to be convinced if the valentine or cincinattti microwave (escort passport etc)was the better. what made you decide on the valentine?

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Post by Shadowmite » Sat Feb 12, 2005 1:00 am

what made you decide on the valentine?
I did of course! Really though, it's the best detector made, it's incredible when you use it, you'll never want to go back.

I personally don't know much about the why radar really works, but I told spy long ago it's just a harmonic or reflection generated by the PLL of the radio's receiving... They use a GUN Diode in a special "horn" antenna for receiving...
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Post by spymongoose » Sat Feb 12, 2005 12:17 pm

By no means do I mean to criticise or bemean you mratatude, quite the opposite in fact. Im a military radar tecnition by trade, and such things are facinating to me. I like understanding radar related devices, and these little detectors are complex enough to fit into my field. the reciver in my radar, in theory, is not terribly more complex than the valentine. I apprciate your comments, and those of others, as they help me undestand better how such devices work. This is the underlying creedo of shadowmite.com, the place where tech heads get together and share knowlege about electronic devices.

As for the valentine, there is no going back once you have owned one. By comparison there is no radar detector on the market (for any price) that gives you the sensitivty/range/awareness that the valentine gives you. the most expensive radar detector i have ever seen was a cobra that sold for $700, and the $400 valentine had it matched or licked in every feature. The valentine is the only way to go. http://www.valentine1.com
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Post by treo2die4 » Fri Mar 04, 2005 10:42 pm

I second the raves for the V1 - I've had one for about 2 years and you're right Shadow, I wouldn't go to another. The location arrows and counter are just too useful. For instance, I was traveling through Boise, ID. Came up on a speed trap that eventually accounted for 12 different cars/motorcycles. As I approach, the detector goes nuts and maxes out at 9 on the counter. I immediately slow down, traffic continues by and 3 people get pulled over. My detector is still reflecting 9 ahead so I stay at the speed limit. One after another people pass me and get pulled over.
The counter slowly decreases to 1 and then shows it behind. I know it's clear so I jack it back up to 90 and continue on. It's an amazing tool that has saved me literally 100s of times. Had a passport previously and although it reported well, I never new where or how many. Get the V1 - it's worht th extra $$.

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Post by mratatood » Sun May 29, 2005 3:10 pm

just got my v1 , i like the arrows but it sure seems to go off alot
i did some reading and turned off my first series passport and the hits reduced a bit, still it goes off alot more in the x band than the passport
is there an adjustment like the highway city sw on the passport?
or do you just lear to ignore the low level hits?

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Post by spymongoose » Tue May 31, 2005 6:05 am

Other than pusing the knob to silence the alarm to the secondary noise level, no. Im glad that is as sensitive as it is, I've had positve readings of over three miles on the freeway under the right conditions. These detectors are serious machines, and are mighty sensitive.
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Radar Detectors

Post by J Squared » Fri Aug 05, 2005 2:53 pm

I drive 200-300 miles/day, and I have a very heavy foot. Just want you guys/gals to look into the K-40 radar detector / laser jammer. I have a hidden sensor and laser jammer in the front grill of my 05 Jeep (5.7L V8 8) ), and a hidden sensor located next to the rear tow hitch. In the interior there are 2 very small red LED lights located inside the dash. They are centered on the roof of the dash, inside the plastic/glass. They can't be seen unless they are lit up. The left light is for the front sensor, and the right light is for the rear sensor. There is also a hidden knob located in a small cubby space just left of my steering wheel. That knob controls the volume of the hidden speaker, and there is also a filter control. This system is so sweet. GOT STEALTH? Actually you bluetooth hackers probably see me a mile away!

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Post by spymongoose » Sat Aug 06, 2005 6:57 am

I did google search for the K-40 detector, and it may just be the snob in me for having paid $400 for the valentine, but I wasnt all that impressed. I saw a radar detector with an integrated laser jamming system, just like you described. The valentine doesnt have an active laser jamming system, however lazer jammers have a very limited effective field of infuence and have been widely regaurded as prohibitive because of the number of jammers required to effectively jam a laser gun. So jammers aside, the detector itself seemed very similar to some of the big name detectors like the cobra line. These are inferior due to a lot of details like quality, lack of a rear facing detector, inability to count different sources of radiation, lifetime support, and the millions of dollars of testing and research by the guy who DESIGNED most of the commercial handheld radar guns. As for the rear sensor you have, I see that as simply a step in the right direction, and something the valentine has had since day one.

As for the amount of driving you do, in a jeep of all things, it sounds as though traffic tickets are the least of your finacial worries. I'd personally opt for a sports car that was capable of actually speeding, and any sports car would get far better gas mileage than a V-8 jeep. Speeding doesnt count untill 15-20 mph over the limit (and up from there... shadowmite currently holds the record of 90 over the limit in a school zone) where the charges go from minor tickes to reckless endangerment and involuntary manslaughter. If your talking about the big leauges of speeding, and not just a heavy foot, the valentine is the way to go.

I dont actually have anything against jeeps, I have seen them do incredible things. Speeding on the highway just doesnt come to mind as thier "cup of tea." The jeep is what I consider to be a 15 mph or less car. 15 mph can be way too fast sometimes... and when those times come I'd want to be in a jeep. When weaving through traffic on the freeway at 120 I prefer a car with a lower center of gravity, and the capability to comfortly kick it upto 140 when you find an open strech of road. I actually found that my mitsubishi 3000GT was the most fuel efficient at 125mph. The low profile allowed the car to slip through the air and the whieght of the car would help energy conservation through the hills and curves. I just dont see a jeep that has a 12 inch lift kit and some fat mickey mud tires to negotiate heavy traffic at 75mph, although I have fantisized about that setupin LA rush hour traffic. I would be able to simply roll right over the moron in his little volvo while he was simultaiously yapping on his cell phone and sucking down his frappiccino. It would be great to feel the whump-whump of the tires and leave wide muddy tracks over such a despicible man and his little yuppie car... But I digress... Having fueled my vehicle today, I weep internally for the dollar amount of gas you waste by driving a V-8 jeep 200-300 miles a day. You could pay for a car in the savings just in gas if you drove a quick little 4 cyclendar rice burner, plus you could even keep your jeep for the approriate occasions. There are some nice ones out there...

Conclusion: I checked out your K-40, and I have no immeadiate plans to replace my valentine. Furthermore, I have no plans to mention the K-40 to any friends in any context other than to mention the innovative use of a remote sensor and integrated lazer jammers. The hidden setup you have is ideal for states who outlaw radar detectors, and for that I appauld you. Keep the setup you have, it sounds pretty sweet.

The big money question... do you experience harmonic interfence from other radar detectors and what causes it?
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