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View Full Version : Discussion I want to build a radar gun

FRAMEDNLVS
Jun 15, 2005, 02:25 PM
gone fishing
mike50
Jun 15, 2005, 04:35 PM
I've built the "Speedy" radar gun and it works, more or less. If you stand at the edge of a street while a car drives by you will get readings that approximate the speed of the car, mixed with lots of other random readings.

I was also able to get readings from my son riding a bicycle, but not from a tinfoil covered baseball. I never tried it on an RC plane.

It only updates about once a second and doesn't have a whole lot of range.

Mike
FRAMEDNLVS
Jun 24, 2005, 02:11 PM
gone fishing
SlopeKing
Jun 24, 2005, 03:36 PM
you can get one for $50 apparently... look in the slope forum
FRAMEDNLVS
Jun 24, 2005, 04:12 PM
gone fishing
SlopeKing
Jun 24, 2005, 04:34 PM
there is a thread called radar guns in the slope forum... read that, it has important info for newbies
FRAMEDNLVS
Jun 24, 2005, 04:41 PM
gone fishing
SlopeKing
Jun 24, 2005, 08:01 PM
absolute rot... the cheap ones work fine, its all about the operator... they pick up my foamies, other people's DSers... theyre fine...
FRAMEDNLVS
Jun 24, 2005, 09:18 PM
gone fishing
Chris Moon
Jul 03, 2005, 12:02 PM
I have the bushnell speedster. It works great for me. Picks up planes very well.
FRAMEDNLVS
Jul 03, 2005, 01:08 PM
gone fishing
Joel
Jul 14, 2005, 11:59 PM
What about a doppler shift measurement...... I know it works for planes with engines and I've seen a post that it worked for a glider, but you had to be really close, I would think an electric motor would be loud enough.

Basically you just record the sound, then use a spectrogram to get the coming and going frequencies and then put the frequencies in a spreadsheet and it tells you the speed and rpm. There is a correction factor for how close the plane passed but I never totally understood how to calculate it. You also need the air temp.

I found out about it from the speed forum on RCU, someone had planned on making a real time "in the field" version, but I guess he never got around to it, although I haven't checked for quite a while.

Its supposed to be pretty accurate and seemed about right when I tried it.

http://www.alphalink.net.au/~hughan/frames.html
http://www.philsrcworld.fsnet.co.uk/speed.htm

It would be awesome if one of you people that are good at this kind of stuff could make a "field" version. I guess a laptop with a mic. on a long extention would be fast enough though, but not as cool.

Joel