Re: TI-H: What we need to concentrate on with the RF
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Robin, Jim, & Eric Barker wrote:
> > But it's legal (which IS important in some countries!) and probably
> > easier to build. It would probably be best to try to design both.
>
> Come on, we can make a legal RF link. It just can't go that far, maybe
> 50 meters. That's all we need. How do you think remote control car
> companies do it?
I know how they do it. (This is Finland, and I didn't make up those
laws.
I just live here. And it's a quite nice country after all...)
1) They use a certain frequency, which is meant to be used for RC toys
and such. I believe it's 27,145 MHz (at least it's printed on my old
walkie-talkies).
2) Then they take the toy to Telehallintokeskus, which is the equivalent
of FCC I believe, and get it tested for any interference. If it passes
the tests, the device may be sold here in Finland.
Any untested radio transmitters are illegal to sell and use, with te
expection of amateur radio transmitters, because the people building
them are expected to have enough responsibility to make their devices so
they won't cause interference. If you would pop open a walkie-talkie and
modify it, for example, by putting some sort of modulator (to connect to
a TI calc) in place of the microphone, ithe device would become illegal
to use.
You must remember that radio transmitters don't just transmit their own
frequency but also a bunch of other frequencies that might interfer with
other radio signals. Also, the range of a signal does not depend just on
the transmitter, but also on the receiver. Radio signals that are meant
to be weak can easily be distored by a signal that the builder thinks
just goes something like 50 metres even on long distances.
That's it, RT links are still illegal here, unless someone starts
manufacturing them commercially and gets them tested. Homebuilt
transmitters are not tolerated.
-Ozone
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*** Osma Suominen *** <a href="mailto:ozone@clinet.fi">ozone@clinet.fi</a> *** http://www.clinet.fi/~ozone
***
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