"A radio transmitter shall be added to transmit the wind speed by changing its frequency. The frequency change shall be 1 Hz per 0.1 meter/sec. The transmitter must be custom designed and built. It cannot be a commercial product. The frequency must be in the 433 MHz ISM band or if a team member has an amateur radio license, an amateur radio free can be used. The transmitter must be able to be set to 8 different frequencies in the 433 MHz ISM band with 25 KHz separation. The team can use a commercial receiver." I cannot make heads or tails of this. Any help will be appreciated! Thanks.
closed as too broad by Bimpelrekkie, akohlsmith, PeterJ, uint128_t, Dmitry Grigoryev Sep 6 '17 at 16:19
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A radio transmitter shall be added to transmit the wind speed by changing its frequency. The frequency change shall be 1 Hz per 0.1 meter/sec. The transmitter must be custom designed and built. It cannot be a commercial product. The frequency must be in the 433 MHz ISM band
- WS is the wind speed in m/s
- B is the band setting (0 to 7) as they want 8 settings spaced by 25 kHz
- C is the carrier (let's say 433MHz)
You need a transmitter which outputs a continuous wave at a frequency of :
C + 25kHz*B + 10*WS
Now, the first and obvious issue here is that, if we want an accuracy of 1m/s on the wind speed, then our 433MHz local oscillator will have to have an accuracy of 10Hz. Same for the receiver. So 5Hz error for both.
That's 1.15e-8 or 0.01ppm accuracy... It can be done, think about custom made crystals lapped under a full moon with some fairy dust on top (very low yield, you can always ask Laptech for a quote), temperature-stabilized ovenized enclosure... ultra low noise circuits... like those. When the applications mention "Radar/Military" and it comes in a thick heavy metal brick with 50 screws on each side, you know it's more expensive than your car.
So your job as a budding engineer is to make a realistic cost estimate for the idiotic requirements you are provided. And then come up with a solution that will work for a budget under $10.
This happened at one of my jobs: every time the boss came back from a ski weekend and suggested a "stupendously innovative" idea, the database administrator would pop up from their screen and quip "no problem boss, that's gonna need about twelve extra servers, plus oracle licenses, sign here".
I mean, if you ask Wenzel for a quote explaining your purpose is to have the teacher learn about some hard facts of life, they'll probably have a good laugh and give you the quote.
- Use a less dumb modulation scheme, for example encode the wind speed information into pulses or binary and transmit that by using FM or AM on your 433MHz carrier.
- It can be as simple as "every time the anemometer makes a turn, transmit a short pulse of RF."
- As said in the comments, modulate the 433MHz with a frequency like "1kHz+10*windspeed".
- Put a ESP8266 on the focal point of a parabolic dish.