Semtech's LoRa (Long Range)

manuka

Senior Member
#1
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
 
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srnet

Senior Member
#3
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 ?
 

srnet

Senior Member
#6
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.
 

manuka

Senior Member
#7
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...
 

manuka

Senior Member
#8
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)
 

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manuka

Senior Member
#10
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.
 

Pongo

Senior Member
#11
Interesting, one assumes all these adopters have checked it out with good results.

Problem with 433 here is that everybody and his brother already has a bunch of devices running there.
 

Pongo

Senior Member
#13
OK, smack me. I'm so used to seeing "SS" that's really just frequency hopping that I didn't realize that this really is SS.
 

Goeytex

Senior Member
#14
In the past Dorji has not stocked any RF Modules in the 900MHz Band, even though they show them on their site. I was able a get a few SI4432's that they had specially made for me. After that the requirement was a minimum order of 500 for anything in the 868/900MHz Band.

For Sx1276/78 in 900 Mhz I suggest you contact Appcon or Nice RF.
 

Pongo

Senior Member
#15
In the past Dorji has not stocked any RF Modules in the 900MHz Band, even though they show them on their site. I was able a get a few SI4432's that they had specially made for me. After that the requirement was a minimum order of 500 for anything in the 868/900MHz Band.

For Sx1276/78 in 900 Mhz I suggest you contact Appcon or Nice RF.
Thanks Goeytex, I see the Appcon modules are on aliexpress for $55.18 a pair at the moment.
 

srnet

Senior Member
#16
Srnet may care to PM me so I can forward to UK.
Will do, thanks.

I hope the Lora modules are a bit easier to interface than Silicon Labs replacement for the Si4432, the Si4463 !

Hope RF have announced a Lora module too, I did email them from the fiftydollarsat email account, asking if there were any samples available.

You would think that given the publicity we have given to the capability of Hope RFs products they would have shown some interest, but I have not had a reply.
 

srnet

Senior Member
#17
My current interest in the Lora modules would be as a replacement for the RFM22 in High Altitude Balloon tracking, at some point in the future the RFM22 will not be available.

From a scan of the SX127X data sheet it looks like it will be capable of direct modulation so FM tones look possible. FSK RTTY may be possible too, and this at 10mW is more or less a standard for HAB use in the UK.

What's not so common in UK HAB use is using data telemetry, but it has several advantages, including the ability to get significant amounts of data downlinked. You can do this with the RFM22 already of course, but the UK licence exempt limit of 10mW reduces range with an Omni antenna to around 12km without an LNA and 50kM with an LNA (at 1kbps). More range is really needed for HAB use.
 

manuka

Senior Member
#18
Semtech's new modules indeed seem capable of other modulation types, BUT the LoRa™ benefits may then be lost.

Thought on that flea power HAB links-perhaps get your ham licence? For a rocket scientist of your calibre this would be a breeze! A wider 70cm spectrum (~10MHz) slice & far higher power (10s of Watts) can then legally be used- there's even a 3MHz sub-band between 435-438 MHz allocated for up and down links to/from orbiting satellites! See =>http://rsgb.org/main/operating/band-plans/vhf-uhf/432mhz-band/
 

srnet

Senior Member
#19
I have had a amateur license for over 35 years ................................................

In the UK the amateur licence does not apply to transmitters on 'airborne vehicles' hence the reason that balloons are restricted to 10mW................
 

srnet

Senior Member
#21
OK-that may be UK specific, although globally FPV (First Person View) flying analog video links abound. Here in NZ I've a Kiwi mate with a ham licence who (AFAIK legally) does ~1W level ~1GHz FPV. Stan. (ZL2APS since 1967)
Yes, it is UK specific.

And the rules around RC model planes here are that you can use FPV at very limited video powers but you (or an observer) must still be able to see the model unaided.

The RC model world here in the UK do themselves no good at all, apart from ignoring the visual sight rule, illegal RC transmitters and powers, video transmitters etc common amongst those that practice FPV.
 
#22
US hams on the ISS communicate with those on the ground with 5 Watt handi-talkies on a regular basis, (although they "may" be running at lower power levels, as the technical requirement for all US hams is to use as little power as is necessary to maintain good contact.) I say "may" because I'm one of the few hams I know who even incorporates convenient power level control into my rigs. The habit of using repeaters on VHF and UHF FM has turned such communications into something resembling cellphone communications, and who thinks about reducing power on their cellphone?
 

srnet

Senior Member
#23
Been playing with Dorjis DRF1278 module, its the bare bones device addressed in the same register centric way as the RFm22 (Si4432).

Its easy enough to make it send Morse and AFSK or FSK RTTY at 200 baud.

FSK RTTY might seem a somewhat old fashioned method of sending messages, but its in common use in the high altitude balloon world for sending back both tracking data and data from cameras. Its used because its extremely efficient, a mere 10mW of transmit power will give you a line of sight range of around 500km, with suitable receiving equipment and an Omni antenna.
 

srnet

Senior Member
#25
Great-any ground range tests? Stan (in Vietnam)
Nope, thats some time off.

The supplied code is for Arduino, and I am getting the usual Windows nonsense getting it to recognise the Mega 2560 boards on my desktop, although my Netbook picks up the driver OK. I suspect its something to do with the new 'improved' and 'unified' driver for Arduino.

I dont see a particular problem translating the code over to PICAXE, driving the LoRa device looks very similar to the RFM22, all I need to do is pick up the sequence of addressing the SX1278 from the Arduino code.

From experience, its far better to have a fully working link, using for example the supplied Arduino code, and then replace the TX and RX sides in turn with PICAXE code. Trying to get both TX and RX working at the same time under PICAXE code might take a very long time, as you cant be sure which end of the link is the problem.

It does surprise me, that despite all the hype around these LoRa modems no-one seems to have done any real world long distance LOS tests, least not that I can find.
 

srnet

Senior Member
#27
I have seen that Italian presentation, and its so lacking in detail that the ‘real world’ tests are meaningless, but I guess it's meant to impress more than inform.

So they achived 8km from the top of a (tall ?) building in the middle of a city to a point (on a hillside ?) some 8km, wow.

Without knowing;

The antennas used
The power used
The data rate used

You can't conclude from the presentation anything that is useful to indicate long range performance, 8km is really not very far and current FSK modules such as RFM22 will achieve that without a problem (434Mhz, 1kbps, 100mW, 1/4waves on a ground plane).
 

srnet

Senior Member
#29
Breaking News ...............

LoRa modem packets from a high altitude balloon , 434Mhz and only 10mW received at 394km using a Diamond X50 colinear antenna on the receiver, about 7db gain.

Thats about the equivalent of 200km on simple 1/4 waves !
 
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manuka

Senior Member
#30
Breaking News ...............

LoRa modem packets from a high altitude balloon , 434Mhz and only 10mW received at 394km using a Diamond X50 colinear antenna on the receiver, about 7db gain.

Thats about the equivalent of 200km on simple 1/4 waves !
Great! Yours? Still going? Which module?
 

srnet

Senior Member
#31
Great! Yours? Still going? Which module?
No, one of Dave Ackermans experimental flights.

They are using the Hope RFM98 (also a SX1278 module) driven by a Rasperrry Pi, which links to the internet to send tracking data to the Spacenear setup.

And working backwards from the bandwidth, spreading and coding rates quoted, the equivalent bit rate is 56baud. The HAB guys often use 50 or 100baud FSK RTTY for the position reporting.

The LoRa calculator says that at those settings the receive sensitivity is -142dBm, some 21dBm better than that quoted for the RFM22\Si4432, and that would appear to be consistent with the sensitivity required to receive a 10mW packet at the reported 394km.
 
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#32
hi, just out of interest, in the us etc do hams have primary use of 70cms, or secondary like us in the uk?
I think one of the limitations in the uk the mod are primary user, and they get rightly upset when people start using
wide bandwidth signals and frequency hopping techniques.
I still wonder why when the foundation licence is such a doddle, that people wanting long range comms don't take this test.
I think that gives access to 10watts. my wife and kids both passed theirs during a half day course at our local radio club.
one of the problems I found with these low power modules is not necessarily the power limit, but the bad selectivity and de-sensing.
in some areas in Lincoln around our cathedral where the local 70cms repeater resides, the radio car keyfobs don't always work reliably.
ive managed to contact the iss, using around 5mW into a 5 section co-linear. I think with these modules though that more selectivity is required.
has anyone on here looked at the signal from these modules on an analyser?
some of the ones I looked at were not very clean signals at all, and most would not have passed any of the spurious emissions tests.
admittedly the ones ive tried were not all that expensive, with two exceptions.
ii would be interested in other peoples results from various modules, this way it may help select various models to suit differing
locations.
regards john
 

srnet

Senior Member
#33
I still wonder why when the foundation licence is such a doddle, that people wanting long range comms don't take this test.
I think that gives access to 10watts.
I presume that those that want long distance comms for amateur radio purposes, talking to other Hams, do exactly that.

Contacting the ISS at low power when both ends of the link has relatively expensive, power hungry and heavy equipment is not going to be difficult.

What radio amateurs are doing is trying to use modules that are around 15mm square, run off 3.3V and weigh under 1g for very long distance low power comms, the modules also happen to be very cheap. They make a lot of things possible that just could not be done in any other way.

The use of wide bandwidth spread spectrum stuff in the amateur band is indeed not a good idea and probably not legal. The 394km 10mW example I mentioned earlier was spread spectrum, but at a bandwith of 20khz in the ISM bands so license exempt and legal. Its not fully clear if wider bandwidth spread spectrum (going across several 25khz channels) is legal, but if 20khz spread spectrum gives an acceptable performance, then it may be a non-issue.

If these LoRa modules do meet the hype, and they are used at license exempt powers, there would be less need for people to misuse the amateur bands for long distance stuff.
 
#34
@srnet
hi
Ive had an amateur licence for over thirty years, and my favourite part of this was using lowest power possible (which was a licence condition) and using datacomms ranging from slow morse
to ax25 packet radio. The point I was trying to identify was that these modules receivers are not very good. Maybe tuned loops could help. Years ago a friend and I achieved very good results
using a 433MHz magnetic loop, with its high Q and narrow bandwidth. Can you use 70cms in balloons or other aerial devices, because I even have to get a notice of variation to use un-attended
operation. The other thing is the charring cross restriction, and other grid references. Ive ordered several of these transceiver modules to see what they will do with greater sensitivity and selectivity.
These 440MHz licence free bands, is their power any higher?
Which co-linear are you using, is it the diamond/comet?
john
 

Goeytex

Senior Member
#35
The point I was trying to identify was that these modules receivers are not very good
How could you possibly make that point as factual without having testing the actual module under discussion? I suggest that your previous testing of other modules is not relevant in regards to the Semtech LoRa device. I would not lump the LoRa device in the same group as the cheapies that you may have tested in the past until valid testing has been done. A start might be to look at the Semtech Datasheet for some specifications.
 

srnet

Senior Member
#36
The point I was trying to identify was that these modules receivers are not very good
Rather depends on what you compare them to. For what they do modules like the RFM22, for their size, weight and cost are very good indeed. They make possible applications that were simply impractical before.

And then along comes the LoRa modules, which appear to have the potential to go very much further than before. The SX1278 is capable of 50mW continuous, and the LOS range (at low data rates) would appear to be circa 500km on simple 1/4 waves, we shall see.

Can you use 70cms in balloons or other aerial devices,
You cant use the 70cms amateur band in any airborne device in the UK (apart from a satellite!).

These 440MHz licence free bands, is their power any higher?
Since you cant use the amateur bands for airborne devices in the UK, the 434Mhz License exempt bands are used, max power 10mW.
 
#37
@goeytex,
What is it that defines selectivity in a receiver, or makes a superheterodyne better than a trf?
Number of tuned circuits, which improve selectivity, or so we were taught forty years ago.
@srnet, how does this work when 434mhz is in the ham band?
Some of these modules five years ago, costing around 40-60 pounds were responding to out of band signals,
and generating them for that matter.
I guess I am trying to find out how you get around these limitations. I understand the need for low power and weight for airborne telemetry,
but how much interference do you get this high up when they must be receiving signals for possibly many tens of miles.
When the mod were conducting over the horizon detection using 433Mhz, you could pick these signals up over vast areas of the uk.
Then there is the other problem of intermod problems, there are so many signals on i.f image frequencies here in Lincoln I had to buy some
quarter wave stub filters.
Again I'm just curious how you cope with that.
Are these lora 50mW modules legal in the uk?, Because with that good range should be easy.
john
 

srnet

Senior Member
#38
Its simply a case of avoiding frequencies that are known to generate QRM, sometimes last minute decisions can be taken to change frequencies, and with these modern frequency agile devices its not too difficult to do that.

Around by me, definitely avoid 434.100mhz and thereabouts, its a very common frequency for remote monitoring stuff, burglar alarms etc.

LoRa modules (or any ISM modules) are only legal up to 10mW for airborne use, nothing stopping you using them at 50mW for land base use under the terms of an Amateur radio license.

It would be ideal if airborne use (at limited power) were allowed under the UK amateur radio licence, like it is in most other countries, but Ofcom do not seem keen.
 
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#39
Hi
Ofcom do not seem to be the once powerful organisation they were. Corporate greed appears to rule the roost, with many commercial interests in uhf bands. I hope its never realised, but there was a consultation
about selling off some or all of the 430-440MHz band. That would be a great shame for a lot of people. You would think with something like television, cable and satellite, do we need to use huge bandwidths for the like
of freeview. I suppose if enough people badgered Ofcom about use of airborne devices, they might listen. If the mod no longer need this band there may be a chance, I guess we will have to wait and see.
regards john
 

Goeytex

Senior Member
#40
@goeytex,
What is it that defines selectivity in a receiver, or makes a superheterodyne better than a trf?
Number of tuned circuits, which improve selectivity, or so we were taught forty years ago.
Yes, that was 40 years ago when most everything was analog. High speed digital circuitry and advanced modulation/demodulation schemes now play the dominant role in receiver sensitivity, selectivity and noise rejection. This is what LoRa is all about, its ability to operate in a crowded and noisy RF environment.

I highly suggest you take the time to read the datasheet.
 
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