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[Reply #15 on:]

Right now, though, I don't care so much about the frequency, I am just wondering how I could design a circuit to transmit wireless signals, from there I could change the frequency. Could I use a 555 timer, maybe?

[Reply #16 on:]

Could I use a 555 timer,

No, not stable enough and will not work at high enough frequency.

Can you take a hint, this project is a non starter, with things like a 555 timer it's not going to be legal even in the US

[Reply #17 on:]

So it is impossible to do micro free wireless. Alright.

I suppose I can just use on of the rf link units once they come back in stock on sparkfun...


baum

[Reply #18 on:]

Sparkfun: don't hold your breath, I have not seen the receivers there since August.
Try the $5 pair, or the next one up.

Want a simple transmitter? Get a "high" voltage, and let it spark to ground - then get a simple AM radio and listen for  the burst of interference that comes in.  Not really practical tho.

If you can make a circuit oscillate, it can be a transmitter, whether intentional or not.
Being able to reliably tune in that transmitter and pick out a piece of data is the hard part.
One way is to have transmitter is transmitting continuously and your receiver tuned into it, and then detect a difference in the signal and report that as different state.
If you're not transmitting  continuously, that makes it harder for the receiver as now it not only has to tune, it has to determine the 2 seperate valid states.
That's the nice part about virtualwire, it takes care of getting enough sent for the receiver to do its job.

Designing RF that works from scratch without tools and the engineering background is very difficult.

Here's a simple thing you can try
http://www.sciencebuddies.org/science-fair-projects/project_ideas/Elec_p024.shtml

[Reply #19 on:]

Get a "high" voltage, and let it spark to ground - then get a simple AM radio and listen for  the burst of interference that comes in.  Not really practical tho.

As well as being not practical, spark transmitters as they are called are illegal in every country in the world.

[Reply #20 on:]

Lots of stuff is illegal, doesn't stop people from doing it tho.
I would think not being at all useful would be more of a deterrent.

[Reply #21 on:]

The 434s also, same price
http://www.robotshop.com/433mhz-transmitter-receiver-pair.html


And a High Sensitivity set for 80 cents more, higher data rate
http://www.robotshop.com/433mhz-high-sensitivity-transmitter-receiver-pair-rxa33.html

[Reply #22 on:]

And a Seeedstudio version as well for $4.99
http://www.robotshop.com/seeedstudio-433mhz-low-cost-transmitter-receiver-pair-3.html

[Reply #23 on:]

i have been using that style with the virtualwire library with great success


(I think Marconi used a spark transmitter to transmit the first signal over the atlantic !)

[Reply #24 on:]

I think Marconi used a spark transmitter to transmit the first signal over the atlantic !

I suspect he wasn't too concerned about EMC back then.

[Reply #25 on:]

and no-one else was transmitting!

[Reply #26 on:]

Thought they just gave it a cool acronym and reduced the power? (UWB)

[Reply #27 on:]

If you build a 'simple' RF link and get it wrong you might block emergency services' or aircraft frequencies... This is illegal and irresponsible.  Buy a pre-built approved module (or become a radio amateur and learn to do it properly - less simple)

[Reply #28 on:]

I'll just get a Nordic.

[Reply #29 on:]

We just got an ad. It showed up on the notification email, not here, though. I guess someone erased it.

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baum