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433MHz remotes with >500ft range

Discussion in 'Electronic Design' started by Joerg, Oct 29, 2010.

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  1. Joerg

    Joerg Guest

    Hi guys,

    Somehow most companies offer all sorts of modules but no "ready-to-sell"
    remotes that are a tad above the performance of keyfobs. What I am
    looking for:

    3 buttons, custom overlay.
    International approvals (meaning 433MHz or 2.45GHz).
    <$20/1k, yearly volume several k.
    Outdoor range a reliable 500ft, ideally more.
    Customizeable codes.
    Works together with a low cost chipset, for example from TI.
    Size max 1.5" by 2", 1/2" high, plus belt clip.
    Integrated stub antenna can be another inch or so.
    Very sturdy, for example ABS.

    I am aware of the Linx brand. Any others? Ideally we'd want to make sure
    two brands work so we have a 2nd source situation.

    Copied c.a.embedded because there may be folks who deal with radio
    controlled embedded systems.
     
  2. TTman

    TTman Guest

    Has to be 433 for 500ft I would have thought......I use Nordic nrf905....
     
  3. You should also check how the link performs with nearby 5-50 W
    transmitters on the same or nearby (hundreds of kHz) frequency as your
    433 MHz link.

    In Europe, the 433 ISM band is in the actively used part of the 70 cm
    amateur radio band, so quite strong signals may also be present at
    that band.

    At least the old keyfob system receivers had very bad selectivity,
    getting blocked by transmitters hundreds of kHz away. A person is
    approaching his/her car, a nearby handheld amateur radio transceiver
    is activated and the operator describes what the car owner is doing,
    when the doors do not open, people seem to do all kind of funny thing,
    when trying to get the car open with the remote control :).
     
  4. JB

    JB Guest

    <snip>

    Speak to John Fairall at RF Solutions here in the UK. They have such a
    product range.
    http://www.rfsolutions.co.uk/

    JB
     

  5. $20 each for a custom controller? Ha!

    More like $200 to $400 depending on options.


    http://www.avalonrf.com/products/digital-data-links/250mw-wireless-digital-link
     
  6. Joerg

    Joerg Guest

    Thanks, but that's a module and we are looking for a complete packaged
    product, with the required papers from agency approval labs.
     
  7. Joerg

    Joerg Guest

    Yes, Paul, I know. But what can one do? Europe doesn't allow the VHF
    bands we have here and the only common denominators worldwide are 433MHz
    and 2.45GHz. 2.45GHz often has range problems.
     
  8. Joerg

    Joerg Guest

  9. dalai lamah

    dalai lamah Guest

    Un bel giorno Joerg digitò:
    EU regulations mandate a maximum transmit power of 10 mW eirp at 433 MHz
    for SRDs (short range devices). It is almost impossible to reach 150 m with
    this power in a reliable way, unless you have a directional antenna and a
    perfect line of sight (two things you can't rely on with a typical key fob
    application). With these regulations and a good antenna you can get a
    "real-life" reliable range of 50-70 m.

    At 2450 MHz you can qualify your device as a "radio frequency
    identification device" rather than a generic short range device. This
    allows you to use powers up to 500 mW. To get 150 meters in a reliable way
    at 2450 MHz you will need a lot of power though, and this isn't good for a
    battery powered key fob.
     
  10. tm

    tm Guest

    Even with a "good antenna" you are still fixed to +10 dBm EIRP. Maybe with
    the
    receiver having the good antenna, you can get better range but then it will
    make
    the receiver directional. About the only way around this is to use a slow
    data rate
    and very narrow bandwidth such as to lower the noise floor and improve the
    system gain.

    tm
     
  11. Joerg

    Joerg Guest

    Yeah, sometimes I wonder what the guys in Brussels were thinking. Or
    whether they were thinking ...

    EU operation on 433MHz would almost mandate AM mode and then tons of
    correlation. All we need is slow push-button control so an effective
    data rate of 10 bits per second or even less would be fine.

    AFAIK they even have a 4W category when not inside buildings but that
    would require some massive battery. And we can't have that.
     
  12. Rich Grise

    Rich Grise Guest

    "Range" problems? Since that's close to the microwave oven freq's, there's
    got to be some kind of joke in there.

    (In America, a "range" is an oven with a stove on top.)

    Cheers!
    Rich
     
  13. Suitable for cooking venison and antelope meat?
     
  14. Rich Grise

    Rich Grise Guest

    And seldom is heard
    A discourging word,
    Because what can an antelope say? ;-)

    Cheers!
    Rich
     
  15. The Avalon RF stuff uses a QAM256 encapsulation.

    The whole idea was to alleviate the dropouts that occur with
    Std FM stuff. It is like the DTV version of a stage microphone with very
    little latency, yet fully digitized, packetized, and encrypted, if need
    be.

    We did a test where we replaced the reel-to-reel recorders on carriers
    with a belt worn "DVR" and all the deck traffic spoke through those
    links. All was recorded on the recorder device, and the Air Boss got
    clean feeds all the time without dropouts. It was pretty cool.
    Integrated it all into the colored deck vests and helmets they wear while
    up on the flight decks.
     
  16. Or use diversity.
     
  17. It is a question of frequency reuse and the difference in population
    densities.

    The radio frequency spectrum is a limited natural recourse and thus as
    many communication links should be able to use the same frequency. On
    HF (especially in the 10-20 MHz) range, the reuse factor can be as low
    as 3 due to the ionospheric propagation (i.e. there can be only 3
    independent communication links at a specific frequency globally at
    similar power levels). On VHF/UHF/SHF the communication range is
    mainly limited due to geometry to distances of 30-100 km, thus, the
    global reuse factor is significantly larger.

    By limiting the transmitter power, the reuse factor can be much
    larger, i.e. more devices will fit into the same frequency range.

    The free space loss is inversely proportional to the square of
    distance, while in urban environment, the received power is inversely
    proportional to the 4th power of distance. Thus, with transmitters and
    receivers well below the roof line, the propagation distance is quite
    limited and a large number of SRDs can be used on a single frequency.

    In Europe, the population density is high in most of Central Europe,
    while in the USA, the population densities outside New England and
    some metropolitan areas is quite low. Thus, a lower frequency reuse
    would make sense in most of USA (i.e. allowing higher power levels).

    I do not want to defend traditional channel exclusive allocation
    systems, since a frequency range is unused most of the time. It makes
    much more sense to use some kind of ALE (Automatic Link Establishment)
    or some frequency agile system (like CDMA) to get the message trough.

    I do not know, if the row about using unused UHF TV channels in the
    USA for other communication has bee solved, but this at least shows
    the problems of packing as much as possible communication into a
    limited frequency range.

    IMO, radio communication should be used only when it is absolutely
    necessary (e.g. moving platforms), but as soon as the signal is within
    a fixed wire/fiber network, the signal should be transferred to the
    wire, freeing up the radio frequency for other users.
     
  18. This requires a quite high SNR.
    Unless you are using some kind of FHSS/DSSS system, the latency would
    be quite large due to the need for using interleaving.
     
  19. Tim Williams

    Tim Williams Guest

    No, measuring resistances... "Ohm, ohm on the range..."

    Tim
     
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