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Radar guns

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Old 12-04-2005, 06:29 PM
  #1  
desmobob
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Default Radar guns

I was just looking at Bushnell's Speedster II radar gun, now selling for about 80 bucks.

Has anyone used one? It seems hard to resist eventually getting one at this price....

Good flying,
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Old 12-04-2005, 07:19 PM
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Default RE: Radar guns

Do some searches. I don't know about this specific gun, but I've seen lots of reports that the less expensive ones have trouble reading small fast objects like planes.
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Old 12-04-2005, 08:01 PM
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Default RE: Radar guns


ORIGINAL: piper_chuck

Do some searches. I don't know about this specific gun, but I've seen lots of reports that the less expensive ones have trouble reading small fast objects like planes.
They are mostly advertised for use in measuring pitching speed in baseball, so I would guess an R/C model would be no problem. That's just a guess, though!

Good flying,
desmobob
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Old 12-04-2005, 08:26 PM
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Default RE: Radar guns

I have a radar gun .... but .... not the one you mentioned. I have found it works best when the object you are reading is comming straight at you. I have also noticed that it is less effective on small planes as opposses to bigger ones. It is a fun gadget. I am still debating how really accurate it is.
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Old 12-04-2005, 11:47 PM
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Default RE: Radar guns

All radars lose accuracy when the object being targeted is at an angle in relationship to the receiver. If you understand how they work--sending out a pulse, and reading the time it takes for that pulse to "bounce" back, then you'd have not problem understanding that they are most accurate when the object is coming straight at them--along the same horizontal plane. Start raising the horizontal plane of the plane, and the gun becomes inaccurate.

My brother has one--I believe the same one you are talking about, and it works good. We have a blast with it. Kind of fun to at least get some idea of how fast the model is traveling!
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Old 12-06-2005, 09:05 AM
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jamie
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Default RE: Radar guns

WHATS THE WEB ADDRESS FOR THIS GUN
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Old 12-06-2005, 05:00 PM
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ORIGINAL: jamie

WHATS THE WEB ADDRESS FOR THIS GUN
Turn off your Caps Lock and Google it.....

Good flying,
desmobob
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Old 12-07-2005, 02:16 AM
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Default RE: Radar guns

Hmmm, most radars like that work from doppler effect. I wonder just how accurate they are as the radar reflections will bounce off the spinning prop at a different rate. That is probably why they become innacurate at times. The size of the plane shouldn't matter. A really good way to determine aircraft speed would be to buy a small handheld GPS and place it inside the aircraft. You can get speed in averages and a reading of top speed. Total distance and track will be recorded too. A much better alternative to radar if you ask me. Not to mention I recall seeing a show on TV about a cop putting forth a lawsuit from being sterilized by his radar gun. It was a long time ago but still worth mentioning. As he would wait for possible speeders he would set his radar gun in his lap. Apparently the thing was really close to his 'organs'. I guess he cooked them over a period of time. Anyway, I personally ain't willin to take that chance even though I have had a vasectomy. GPS doesn't emit harmful radiation. And it is probably far more accurate and you can take it on trips with you as well.

Good luck,

Wes
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Old 12-07-2005, 09:52 AM
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Default RE: Radar guns

Doppler effect simply differentiates between objects (in the case of weather, air) moving toward the receiver with objects moving away from the receiver.

First off, the plane (and propeller for that matter) are all moving toward the receiver, so there would be no differential to measure.

Second, I doubt that this technology is built into a 99 dollar radar gun.
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Old 12-09-2005, 02:19 AM
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Default RE: Radar guns


ORIGINAL: 2slow2matter

Doppler effect simply differentiates between objects (in the case of weather, air) moving toward the receiver with objects moving away from the receiver.

First off, the plane (and propeller for that matter) are all moving toward the receiver, so there would be no differential to measure.

Second, I doubt that this technology is built into a 99 dollar radar gun.
Thanks for setting me straight on that 2slow. You forgot to mention what you thought of putting a GPS on board. Only if the craft has enough room and power to carry it of course.

Wes
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Old 01-20-2006, 09:51 AM
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Default RE: Radar guns


ORIGINAL: 2slow2matter

I doubt that this technology is built into a 99 dollar radar gun.
I believe all radar guns use doppler techniques to get a reading. I know the cheapy Bushnell Velocity I owned had it. But I found that the operator had to stand in harm's way to get a reading, and the gun doesn't even lock on the high speed, so the user has to look at the display and not the target. That's double jeopardy!

I now have a Stalker Pro which is a 36 gigaherz doppler Ka band radar. It was a LOT more money, but it reads composite f3J sailplanes from over 500 feet away, has auto peak hold, and can clock a truck on the interstate from 10,000 feet and a car from more than a mile away. It is so sensitive that a buddy of mine rightly claimed, "You almost don't even have to aim it for a reading". We use it for Dynamic Soaring where speeds are commonly in the 80 mph. to 200 mph. range.

ps. I've heard that just pointing it down the interstate lights up everybody's brake lights as their detectors go off!
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Old 01-20-2006, 11:24 PM
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Default RE: Radar guns

Hi,
Just to clarify some information re the radar guns. Most 'radar guns' discussed do involve the doppler shift frequency system to dermine a speed of a moving object. The radar works by emitting a continuous beam of electromagnetic energy at a specific frequency. A moving object, whether it be toward or away from the instrument causes a change to the emitted frequency. As the changed frequency is received back at the instrument, the changed frequency is used to calculate the closing rate speed of the object and the instrument.

Basicly, the change in frequency and the '0' speed of the instrument and the transmitted frequency are used to convert the change in frequency to a speed reading. phew......

In regard to the angle of the instrument towards the target, it is important to reduce the 'cosign effect' as much as possible to obtain a more accurate reading of the speed of the target. A 0 degree (head on to target) will give an accurate reading. The greater the angle of the target towards the instrument the lower the speed reading on the instrument.

The spread of the beam of the radar guns is also a critical factor due to the nature of the emmitted frequency. At approximately 100 meters, the beam width from most radar guns and vehicle mounted radar is approximately 40 metres. This can cause the instrument to receive changes of frequency from multiple targets or aircraft.

The most accurate form of speed measuring device available is a Laser (LIGHT AMPLIFIED BY STIMULATED EMMISSIONS OF RADIATION) device, commonly known as a LIDAR (Light detection and ranging). The 'laser' beam goes out at pulses and the time of flight of the pulses are measured on the return and the speed is calculated.

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Old 01-21-2006, 03:19 AM
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Default RE: Radar guns

Flapper is correct about the radar info. I use one at work, (yes, to catch speeding vehicles) and hold a certification in the use of doppler radar speed measuring devices. I have also had one used to measure the speed of my RC plane, and it does work. The radar does not pick up smaller objects like airplanes as easily as large objects, and if there are any moving cars within the scope and range of the radar, it will readily pick up that vehicle instead of your plane. There are also many types of interference that can cause you to get an inaccurate reading; however, it will be obvious. Estimate how fast you think the plane is moving, then measure with the radar. If it is much slower or much faster, you may be experiencing interference.

The cosine effect that was mentioned before refers to the radar providing a slower than actual reading due to the object moving at an angle to the radar antenna. Basically, your reading becomes less accurate the higher the angle. So, to get the most accuracy, the moving object must be moving directly toward or away from the radar antenna's signal.

I don't recommend spending all the money on a police radar. You don't need all the certification that police need to win cases in court. Just make sure it has the speed range for the planes you are going to measure. Some radars don't detect beyond 120 or so mph.

LIDAR's are just a different technology for measuring speed in the same way as the radar. You still have to worry about the cosine effect, but they are less prone to interference since the laser beam is pointed directly at the object and not at a large area encompassing the object. The GPS system may cost more than you are willing to put into it, but if you got the cash, that would probably be the most accurate way. It, however, measures speed horizontally in relation to the earth's surface, so if you are climbing or diving, your reading will be slower than actual.

None of these devices measure airspeed, mind you. You would need a miniature pitot tube and an airspeed measuring device inside the plane.

In short, I recommend you spend the $80 and get the cheaper radar.
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Old 01-21-2006, 05:09 AM
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Default RE: Radar guns

Patto,
We share similar occupations. NSW Highway Patrol 10yrs experience currenlty using Silver Eagle Radar and Pro Laser III Lidar. Also have used KR10 and 11.

Regards
Flapper
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Old 01-21-2006, 10:10 AM
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Default RE: Radar guns

If you just want to use the radar a few times for grins, then it's silly to spend more than $80, but if you're going to measure aircraft with any speed, you'll be disappointed. I couldn't even get the ol' Bushnell to get a reading on a 15 pound turbine until it was 50 feet away. At that distance the angle was about 30 degrees which meant a correction of almost 15%.

That's the main reason a long-range radar is worth it, as it will track the plane even when it's just a speck in the sky.

Furthermore, when measuring DS or very high speed (over 100mph) objects, the lowbuck radar only picks up the speed at the very last moment when the plane is headed absolutely direct at the user which may not be it's fastest since it's likely in or at the end of the turn the pilot must make to miss the gunner.

The acid test is: Would you let someone that you care for stand within 50 feet of a speeding object, headed directly at them?

-My two cents-
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