Hi.
I started this topic just for curiosity, is it very complex building a weather radar? I´m not thinking in a full range weather radar (up to 300km - >3m dish + amplifier), but more a weather radar with range of 40km (used in ships or airplanes) or even less range, 10km.
I´ve seen a lot of sensors on ebay (like Doppler Radar Wireless Module) using X-Band (X-Band have better resolution than C-Band)..does this sensors anything related with weather radars technology?
Thanks.
is it very complex building a weather radar?
Yes.
Radar works by sending out a pulse of microwaves. By working out how long it takes the waves to be reflected back, you can work out the distance away an object is.
Imagine an object is 1km away. The speed the waves will travel at is the speed of light, or 299 792.458 kilometres per second. That is 2*(1/299792.458) seconds before the reflected waves can be detected, or 6.6712819 × 10^-6 seconds. This will work out at approximately 0.00000667 seconds between sending out a microwave pulse and receiving it again. The arduino crystal pulses at 16MHz, or 16000000 times per second. That makes one pulse 6.25 × 10^-8 seconds in duration, or 0.0000000625 seconds. 0.00000667 / 0.0000000625 = 106.72, or 107 pulses between transmission and receiving it.
It is possible to measure this time with an 8 or 16-bit counter, both of which sit inside that IC that makes the arduino work. So theoretically, the software is possible. Now for the hardware...
The radars I have seen for small boats have either a 2 or 4 killowatt power consumption. That is one heck of a lot of power! Voltage*Current=power. Mains voltage (here) is 240V. 4000/250= a 16 amp current draw. These radars can detect objects ~24km away. 16 amps at 240 volts is easily enough to kill you. The microwave radiation could be harmful, but it depends on the wavelegnth, frequency and exposure, as well as whether you beleive the sceptics. Next, you need to process the data.
Although it can be done, it will not be easy. And that's assuming you can find a microwave transmitter and receiver...
Onions.
P.S. https://buy.garmin.com/shop/shop.do?pID=13490&ra=true 4kw radar, cost:£1799. All that money should say something about the complexity...
The doppler unit won't have the range you mention, though it could be used to tell you how fast the tornado is moving, just before it hits you.
Simple doppler won't give you range either.
Always bear in mind the inverse square law.
I've been playing with that sensor. It works well out to about 50 feet with something like a 120 degree beam pattern in azimuth, 60 degrees in elevation. Not so great for weather systems!
Within that beam pattern it'll tell you the speed of objects, but not the range. Doppler radars with range capabilities are "pulsed," where a pulse is sent out and the phase of the received pulse is measured to get the range per the speed of light. This sensor doesn't have this capability. You can operate it in what the data sheet calls "pulsed" mode, but that just allows you to save on power consumption and doesn't involve any capability to measure the phase of the returned pulses. It's pretty much a black box. You apply power and ground and you get an IF signal out, containing the difference (doppler) frequencies, conveniently located in the audio range. E.g., a 100 mph object produces a ~3100 Hz signal. The most basic mode is "continuous wave" mode where the transmit antenna (consisting of two small patches on the pcb) continuously emits the x-band signal, and the receive antenna (similarly two patches on the pcb) continuously receives the reflected signal. As I say, the pulsed mode allows you to reduce the duty cycle to conserve power, although the unit isn't too power hungry--30 ma @ 5V.
Joe
Hi.
Thanks for the answers, my idea was to measure rain.. but after reading yours answers, its too much complicated even for a small radius range 
This project looks great
http://members.inode.at/576265/rainradar.htm
He is following a 5Ghz rain scatter project (3 meter dish 
)
http://www.dl6nci.de/oe5vrl.htm