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'[OT] Tech America RF modules'
1999\10\05@123338 by Adam Bryant

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All,
Browsing through the latest Tech America (now Radioshack.com) catalog, I
came across the following RF Transmit/Receive modules.  As the question
of where to buy RF modules appears frequently on the list I thought I
would pass along this info FWIW.

Cat #: 900-6896 Mfr's #: TX433  UHF Transmitter 433.92MHz       $9.85   3-12v
operating voltage range, 200 meter range.
Cat #: 900-6895 Mfr's #: RX433  UHF Receiver 433.92MHz  $9.95   4-5.5v
operating voltage range.

If anyone has used these modules, please provide us some feedback.  These
look perfect for a semi-autonomous (a la Mars Sojourner) robot I have
been thinking about building (PIC based, of course).

Adam Bryant (age 0x23)
spam_OUTabryantTakeThisOuTspampeaktech.com (work)
.....adamdbKILLspamspam@spam@juno.com (home)
Parker, CO, USA
Robotics, RC Airplanes, anything using a PIC

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1999\10\05@134554 by Dan Larson

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I bought a pair.  They work.  I fed a 1Khz square wave
into the transmitter and scoped the receiver output.
I have not actually used them yet for data, but I imagine
that a set of Holtek remote control decoder chips would
work well, or you can roll your own serial protocol.

One thing I would recommend, if you roll your own
protocol, is to make sure that on and off time
are balanced. An NRZI type algorithmic perhaps...
(Please don't ask *me* about NRZI, I only mention
it because I know of it as one of the balanced
code schemes out there.)  The receiver as a very active
gain control and you don't want it jumping all over trying
to track the average energy of your carrier as it
bounces all over.

If and when I get to it, I'll share my success / failure
with the list, but it will be a while.  Too many other
tasks and too little time.

Dan

On Tue, 5 Oct 1999 10:30:16 -0500, Adam Bryant wrote:

{Quote hidden}

1999\10\05@141120 by Steve Kelley

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Adam . . . .
I guess it depends on what use the * RF * communications will be put to.
Radio Shack has offered a large selection of * Remote Control * cars ,etc.
and usually these are going to use some limited encoding , like is offered
by * Holtek * parts.  Moving up to producing a data link , may require a
design using * RF * componants ( i.e. RFM Xceivers ) that have a faster
rise / fall time of the modulation.  I was faced with this recently and had a
design that used a very narrow detection window.  The majority of the parts
that I came across ( for xmitting ) would operate with rise /fall times at about
100 to 150 usec. max.  So , even though this timing might work for a 1 kbps ,
OOK transmission , if the receiver is looking for fast transistions . . . . . oops!

The RFM 3001 ,3002 , 3003 are xmitting with rise /fall times that average 6 to
12 usec. and provide for up to 119 kbps.  

Steve

{Original Message removed}

1999\10\06@030506 by Anne Ogborn

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I've used them. They're pretty weak, 200 meters is optimistic at best.

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