From: John De Armond Newsgroups: rec.outdoors.rv-travel Subject: Re: UK speeding ticket Date: Fri, 30 Nov 2007 19:00:32 -0500 Message-ID: <om61l35h9nn043hcj4mki3r7o97e25nqks@4ax.com> On Thu, 29 Nov 2007 22:47:09 -0500, "Tom J" <tomnews@earthlink.net> wrote: >Allan F Damp wrote: >> A friend sent the following message. It may be completely "urban >> legend" but it does have a modern technology ring. >http://www.snopes.com/horrors/techno/radar.asp >This farce has been around for 8 years!! Why don't people check out >this junk before posting?????????? The same thing is happening on >both sides of the political debates - 1 false email after the other >just full of outright lies!!! What an ass. Are you ill, Tom? Off your meds? You're about to surpass sill as the ass of the group. I bet you pissed yourself scampering to snopes, a site about as reliable as wikipedia. You need to take a good hard look in the mirror and see if you like what you see. As the OP noted, the tale as told is undoubtedly false, but as with many such stories, there is an underlayment of fact. Several of the Soviet anti-air missiles operate on the X-band. During the Vietnam war, many pilots purchased off-the-shelf "fuzzbusters" and mounted them on the canopies to alert them to incoming missiles. This was before the planes were equipped with suitable threat warning receivers (TWR). There was a nice article about this in Car and Driver magazine that prompted many folks including my dad to buy a radar detector and send over there via the VFW. Snopes is flat wrong about the characteristics of police radars. Nothing new there. I currently own 3 police radars, have owned many others, have analyzed the performance of most of them and am certified in TN and GA as a traffic radar expert witness. 70s era (undoubtedly when this story started) radars that used the 2K25 pencil klystron tube as the microwave source emitted in the 1 watt range in front of a fairly high gain dish. While the effective range of the units were limited because of primitive receivers, the signals could be received for tens of miles line of sight. Even 90's vintage radars emit in the 10s of mW and can be received over several miles. Atmospheric anomolies that caused ducting and refraction would greatly extend that range at times. While the emitted signal was nominally continuous wave, the signal was modulated by ripple from the high voltage inverter in the control head. This resulted in a signal that sounded much like that of a Soviet anti-air targeting radar. (I've heard recordings of the latter.) It is quite probable that an early pre-digital signal processing TWR would receive this police radar signal and alert. The early units did not present PPI information; instead only lighting a warning light and sounding a tone. More modern ones can develop PPI and differentiate signal types. Some info: http://www.fas.org/man/dod-101/sys/ac/equip/an-alr-69.htm Later models of police radars such as my Kustom Signals HR-11 operate in pulse mode. The emitted signal would look very "missile-ish" to a TWR. The latest radars such as the Stalker operate in a wide band "chatter" mode designed to defeat civilian radar detectors. (it doesn't). Again, similar to modern military radar signatures. In general, police radar technology has followed military radar by a decade or so. Snopes' claims to the contrary are completely wrong. Anti-radiation (HARM) missiles are designed to lock onto a radar signal and fly toward it. Early HARMs had only simple 4 quadrant receivers that required the emitter to remain on during the entire flight. By the end of Vietnam, HARMs had the ability to compute a vector to the target and fly to it even if the signal is turned off. Since police radar operates in the same band as Soviet armaments and emits a signal similar to its radar, it follows that a HARM missile could indeed seek to a police radar. That's the factual part. Here's how I imagine the story got started. Some fighter jock somewhere in the US, undoubtedly on a training mission, has his TWR alarm to a police radar. He located the source of the microwaves and saw that it was a cop running radar. The pilot had fantasies of pickling off a HARM and blowing the cop off the highway. In lieu of actually doing that, he combined his training with a little creativeness and made up that story. Who knows? It might even have gotten written down and sent to some cop shop as a joke. A somewhat similar real-life incident was reported via the Forest Service's Radio Service network when I was moonlighting as a radio engineer. An AP had set up his police radar oriented such that it was line-of-sight with the base's main traffic control radar. There was sufficient harmonic energy in the beam to damage the police radar's primitive receiver. The FSRS back then offered its radio repair services to small police departments. The tech bulletin was sent out so that we'd know what to look for if we received police radars in for repair that had mysterious receiver failures. John |