

Setting Up a Radio System from Scratch - silentbicycle
http://spin.atomicobject.com/2014/05/16/radio-system-from-scratch/

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adestefan
The reason why you can find these modules is because 434MHz is an ISM band in
some parts of ITU Region 1. You won't find an garage door opener there in the
US. In the US you should use the 315MHz version which allows for license free
use.

While 434MHz is in the 70cm amateur band you really should have an ID coming
out of this thing when it transmits. All you need to do is shove your call
sign out at 20wpm Morse code at the end of your transmission.

Otherwise it's a cool little hack.

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tlrobinson
There are some comments on the SparkFun page suggesting these transmitters are
"Part 15" compliant (or at least can be, if only transmitting intermittently):
[https://www.sparkfun.com/products/retired/8946](https://www.sparkfun.com/products/retired/8946)

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th0ma5
This is really great for both the Amateur Radio community (proper) as well as
amateurs of radio concepts. Like a lot of things, computers are becoming more
and more things in more and more places. Your grandfather's crystal set is
today's DSP with an Arduino. That's just fantastic.

~~~
silentbicycle
Software Defined Radios are also fascinating! That's a very different post,
though. :)

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jstsch
Nice post. For a slightly more comfortable setup the Arduino based JeeNode's
([http://jeelabs.org](http://jeelabs.org)) are worth mentioning. Super low
power and quite a nice library.

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kabouseng
For frame syncing you can also have a look at Hoffman-Neuman sequences,
applying convolution between the expected frame sync sequence and the
incomming bit stream.

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officialjunk
Is it necessary to periodically transmit? What are downsides to only
transmitting on state change?

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silentbicycle
There's no way to know that the payload has been received - they're
transmitters, not transceivers. The messages are idempotent anyway, so just
retransmitting makes the whole system simpler.

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stcredzero
I thought this would be yet another reference to a sci-fi story where someone
is marooned on a planet with nothing, and they use their chemistry knowledge
to re-implement enough metallurgy to build a spark-gap radio and get rescuced.

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dmitrygr
I'd read that

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groby_b
You have read Andy Weir's "The Martian"? ([http://www.amazon.com/The-Martian-
Novel-Andy-Weir-ebook/dp/B...](http://www.amazon.com/The-Martian-Novel-Andy-
Weir-ebook/dp/B00EMXBDMA))

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nsxwolf
Or use Wifi, Bluetooth, Zigbee, :)

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mbrameld
It's almost like you didn't even read the article...

