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Thread: Semtech's LoRa (Long Range)

  1. #1
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    Default Semtech's LoRa (Long Range)

    Semtech's LoRa (Long Range) spread spectrum technology suits demanding 433 MHz wireless data links, & could merit a quick heads up by those after "smell of an electron" performance.

    Dorji have just released a DRF1278DM LoRa based module with claimed RX sensitivity of -136dBm. Price in US$20 range. Stan
    Last edited by manuka; 13-08-2014 at 12:48.

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    Interesting, -136 dBm is 0.0355 microvolts (50 ohms), gotta give that a try.

    Tindie has a link for us US folks, $23 shipped.

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    As a comparison, the Si4432 claims -121dBm (although I suspect its closer to -116dBm) and that manages 40km LOS on simple 1/4 wave antennas.

    Now an extra 15dBm of 'sensitivity' if fully realised should represent circa 6 times distance, so 240km maybe ?
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    srnet: Guessed you'd be interested-even if performance not quite up to geostationary "$50 sat" duties!

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    Sounds perfect for use with a long-boom beam, manuka.

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    Quote Originally Posted by manuka View Post
    srnet: Guessed you'd be interested-even if performance not quite up to geostationary "$50 sat" duties!
    I did discuss the Semtech device with one of their techies around this time last year, but it was too late to incorporate for $50SAT.

    The sensitivity in standard FSK data seems about the same as the Si4432, and its not clear if the more advanced spread spectrum modes, which need accurate frequency control, would operate satisfactorily when one end of the link (the satellite) is subject to such large temperature changes as well as large Doppler based frequency shifts.

    And at the moment wide band spread spectrum operation is not quite what the IARU had in mind when allocating satellite frequencies.

    I can see why Dorji have put an intelligent front end to the module, using such devices from scratch can be a bit daunting at first. However its the direct access to the devices registers that makes the Si4432 so versatile. With a simple £3 module, you can do a reasonable simulation of FM, so you can send both slow Morse and fast Morse data as well as AFSK RTTY. And you can also use it as a FSK device and thus send FSK RTTY and FSK (CW) Morse if you wish.

    If I were to be sent a couple it would be interesting to do a direct comparison with the Si4432\RFM22 between a couple of the local hilltops.
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    I've put my hand up for similar! In fact Dorji's DRF1278DM module (which uses the SX1278) looks to best suit battery friendly point to point work in demanding terrestrial environments.

    According to claims (sourced here but somewhat abridged & edited)-

    Spread spectrum technology has been utilized for a number of years, but has not been available until recently as a low-cost solution suitable for low UHF band sensor networks.

    Most deployed 433 MHz sensor systems for metering, security or industrial automation are limited in range to just a few km in a suburban environment (with a simple whip antenna). However, using the LoRa technology, the SX1278 boosts this to more than 15km, and typically 3km in dense urban conditions.

    The additional range provided by LoRa eliminates the need for repeaters in these applications, significantly simplifying the system design and lowering the total cost of deployment.
    Keep in mind the legal 433 MHz ISM band is limited to just 10 or 25 mW Tx power, & is only 1.6MHz wide. As the SX1278 is optimized for the rapidly growing Chinese smart meter market (apparently using 470-510MHz), spread spectrum benefits may be lost if the SX1278 is throttled back to lower power & a narower band slice...

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    Semtech's LoRa™ seems to be flavour of the month in China, & well established Chinese wireless data firms HopeRF and Appcon (both based in the e-powerhouse city of Shenzhen) also now offer LoRa™ based modules.

    Appcon (who intend a 500mW version mid Sept 2014) have their 100mW APC340 pdf here,c/w the year 2014 repeatedly shown as 20114 ! Sigh- such basic typos don't inspire much confidence in claims...

    However they relate that tests have shown SX1278 based 433 MHz APP340 penetrating ability as -

    => 7 floors at 4.56Kbps totally inside their office building & away from windows
    => 2.2Km at 9.11Kbps in Shenzhen city on an straight road (c/w cars,trees,bridge & MEGA e-noise)

    Stan.

    EXTRA: Not just China -see here for impressive SX1272 (868MHz) EU field trials (scroll down to P.9 & 10)
    Attached Images Attached Images
    Last edited by manuka; 19-08-2014 at 08:07.

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    Do you think Dorji will release an 800/900 MHz SX1278 based module?

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    Pongo: Shenzhen sourced UHF wireless data modules often seem "badge engineered",so I suspect they may (although probably SX1276 based).

    Higher freqs of course have lower band noise & more compact antenna, but there's greater path loss & less ability to punch thru' obstacles. 800-900MHz is globally rather an allocation fruit salad too. 433 MHz gear tends to appeal for it's near universally available ISM band slot. As a radio ham (ZL2APS) I can run higher power & wider "70cm" band allocation etc if need be too.

    Asian arm twisting may soon see some 433 MHz LoRa™ Dorji modules in my hands for claims verification & "PICAXEability". Srnet may care to PM me so I can forward to UK.

    News to hand: This is a fast moving field - MicroChip are adopting LoRa™ ! Stan.

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