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Cheap 433 Mhz Serial TX & RX - Which ones!

Discussion in 'Electronic Design' started by Kevin Walton, Nov 18, 2003.

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  1. Kevin Walton

    Kevin Walton Guest

    Hi All

    I'm looking for a pair of cheap 433 Mhz Serial TX & RX modules to send
    GPS information from a model airplane back to a laptop on the ground.
    It's the first time I hzve played with these modules and I'm just
    overwelmed by the level of information and choices around.

    I need a 4800 baud data rate for the GPS and I'd like to feed Serial
    directly in and get Serial directly out, but can do some work on
    Veroboard for level changers or encoders etc if I need to.

    The Renton LC-434 modules:

    http://www.rentron.com/PicBasic/RemoteControl.htm

    look quite good, but are in the US and quite expensive (40 USD plus
    shipping for the pair).

    Most of the options on http://www.rfsolutions.co.uk/ in the uk that I
    can find avaliable don't talk about serial options.

    What can I buy from RS, Maplins, Farnell or another supplier to do the
    job simply and cheaply for me (25 USD, 25 pounds type level)?

    Sorry for the simple question but I'm a bit overwelmed with all the
    options right now and supprsingly can't find anyone who has done
    exactly htis before on the web!

    Cheers
    Kev
     
  2. I have just accomplished the similar project.
    The important consideration is the need for licensing in the different
    countries.
    The operating distance should be 2..3km at least. That means you can't
    go with a garage opener transmitter or Bluetooth device.
    RS232 over wireless is definitely not the best choice. It is very error
    prone and unreliable. 4800 bps is too slow if you are looking for GPS
    updates every second.
    I used packetized PSK transmission with FEC.

    Consider Aerocomm modules.
    Here I am.

    Vladimir Vassilevsky

    DSP and Mixed Signal Design Consultant

    http://www.abvolt.com
     
  3. Tim Auton

    Tim Auton Guest

    What about their "Low cost FM transceiver", 2-way (which you don't
    need) but it takes serial logic levels and does all the buffering,
    encoding, decoding etc. for you. £34 a pair.
    Have you looked at Rapid Electronics? You can download the "Security &
    Warning Devices" bit of their catalogue as a PDF from

    www.rapidelectronics.co.uk

    They supply RF Solutions stuff as well as LPRS "Easy Radio" modules, a
    pair of "Easy Radio FM transmitter and receiver" would set you back
    just under £30. They also do all the encoding/decoding business for
    you. I've used Rapid Electronics before and they live up to their
    name. They also sell enconding/decoding chips and the like (and of
    course the full range of the rest of the electronics gubbins you could
    ever want).

    I don't know how much range you want, you'll not get a whole lot for
    £25 (200m or so with small omnidirectional whips) and you should look
    at the licensing requirements to see how much transmit power you are
    allowed. You could use a directional receive antenna for more gain
    and/or be naughty and overpower a transmitter a bit and use something
    other than the 1/4 wave whip transmit they are approved for. That
    would of course be illegal, but I doubt anybody would even notice in
    the wide-open spaces you need to fly a plane.


    Tim
     
  4. Tim Auton

    Tim Auton Guest

    Sorry to follow myself up, but if by "serial" you mean RS232 then
    something like a MAX232 would do you for the Rx logic level > PC RS232
    interface.


    Tim
     
  5. Kevin Walton

    Kevin Walton Guest

    Hi All

    Thaks for the info, google seems to have lost my first reply so I'll
    go over it again here.

    Yes Serial = RS232, 4800 baud ASCII (NMEA) out of the GPS, into a
    laptop, as though they are directly connected.

    Distance wise, 200m quoted ground to ground should give me a fair bit
    more for air to ground I think and 400m should be enough. In remote
    locations I'm happy to play with a little more power and different
    aerials :)

    Will have a look at the specific recomended solutions.

    Cheers
    Kev
     
  6. Kevin Walton

    Kevin Walton Guest

  7. Luhan Monat

    Luhan Monat Guest

    Try these, there cheap. $4 transmitter, $5 receiver.

    http://www.mouser.com/index.cfm?han...uctid=446416&e_categoryid=132&e_pcodeid=50900
    RCR-433-RP Radiotronix Embedded Wireless Modules Distributor - Mouser
    Electronics - Electronic Component Distributor
     
  8. Randy Ott

    Randy Ott Guest

    Kev,

    I would suggest you take a look at local regulations. For example, in the
    US, FCC regulations put a limit on the duty cycle of these 425-435 MHz
    transmitters. This makes them useful only for remote control. The cheap
    ones use OOK modulation which would be difficult to use with an NRZ data
    stream.

    There are some transmitter/receiver modules available as a "wire
    replacement" but they are not so cheap.

    You can see an example at www.radiotronix.com

    Randy Ott
     
  9. Radiotronix is not going to work for model airplane. The operable
    distance of their modules is about 100m max. Also, you have to apply for
    license.

    The good transmitters for a few km range are build by Aerocomm,
    DataRadio.

    Vladimir Vassilevsky

    DSP and Mixed Signal Design Consultant

    http://www.abvolt.com
     
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