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OA47

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Posted: 04:00pm 03 Sep 2017

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I am about to order some LORA modules from that well known auction site and was wondering if there were any comments or recommendations from shedders. I wish to monitor some sensors via Micromites (up to 20 units) that will be located in the field up to 3 KM from the nearest internet connected PC which is approx. 100KM from my SHED. My requirements would be to have a low standby current as they will need to be solar powered and an RS232 port as I would anticipate that the data could be transmitted via the console port to the receiving unit and also give remote access to modify the program on the Micromite whilst it is in its initial operation.

Here is a link to some units that have my attention:
433Mhz LORA modules

I would appreciate any comments from the learned shedders.
Graeme

Grogster

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Posted: 09:01pm 03 Sep 2017

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I have not used those ones, but any reason you are not considering a couple of HC12's?

They also have 100mW output, multiple channels etc, and are only about $5 each.
Even cheaper then that if you buy ten or more in one go.

Be aware that you'd be hard-pressed to get 3km out of 100mW - even line of sight.
I suppose if you had lots of height(IE: No obstructions), and directional antennas with some gain.....

I would be looking for more juice then 100mW if you need 3kM.
Radio regulations would also come into play when you need to transmit that kind of power to get that kind of range.

Can you please confirm that your 3km and 100km statements are correct and not typos.

Smoke makes things work. When the smoke gets out, it stops!

OA47

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Posted: 09:13pm 03 Sep 2017

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Thanks for the reply Grogs. I sorry if my post was a bit ambiguous. I am aware of the HC-12 units but the radio range needs to be a reliable 3 km that is why I have been studying the Long-Range (LORA) variety of the modules. I believe that the spread spectrum mode of these devices gives them the ability. It is the controlling and data gathering PC that is 100Km away and the one that I would connect to via the inet.

lew247

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Posted: 09:16pm 03 Sep 2017

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Hc-12's are only very short range and the data transfer is very fast
The Lora modules are specialist units that do work up to several Km's away - brilliant for long range but slow data transfer so can't be used for things that need fast data transfer
3Km with those modules is no problem even with the very low power output

a review on them here

and an indestructable articlehere Edited by lew247 2017-09-05

OA47

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Posted: 09:22pm 03 Sep 2017

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Lew247, I am afraid that the first hyperlink you posted has been hijacked.
https://www.facebook.com/uniladmag/videos/2283040031719043/

EDIT:
2nd One looks OKEdited by OA47 2017-09-05

lew247

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Posted: 09:43pm 03 Sep 2017

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OA47 said Lew247, I am afraid that the first hyperlink you posted has been hijacked.
https://www.facebook.com/uniladmag/videos/2283040031719043/

ARGHH... no idea how that happened sorry. I can't edit it now either. never saw that happening before, because it was a copy and past of a review I was reading - it was nothing to do with facebook at all

The link was actually this page http://vanderleevineyard.com/vineyard-blog/long-range-wireless-networking-module-reviewEdited by lew247 2017-09-05

Grogster

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Posted: 10:46pm 03 Sep 2017

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I stand corrected.

Might have to get a couple of those to play with myself now.

Clickable 1st link...

Edited by Grogster 2017-09-05

Smoke makes things work. When the smoke gets out, it stops!

srnet
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Posted: 10:43am 04 Sep 2017

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OA47 said Here is a link to some units that have my attention:
433Mhz LORA modules
/QUOTE]

Those are UART front ended LoRa modules, so they may not have a sleep mode.

A native SX127x LoRa device is addressed via an SPI interface. These modules are easy to put to sleep and consume only a few uA. Not difficult to drive either.

For your application LoRa is the way to go, nothing else will come even close to the range. Its not possible to be specific, as environements vary so much but 3km would be trivial for LoRa, you may only need 2dBm\1.6mW for sensor reading applications. The LoRa modules (RFM9x, DRF127x) are capable of 50mW, but your not going to need that sort of excessive power unless the 3km is through dense and wet forest.

I did publish some Micromite code for the LoRa SPI devices a couple of years ago, not a lot of interest in it really.

Lots of stuff on the capability of LoRa here;

https://github.com/LoRaTracker/Test-Reports

The report "Semtech LoRa Transceivers � a KISS approach to Long Range Data Telemetry - January 2015" compares a typical FSK style tranceiver (RFM22B) with a LoRa device.

Edited by srnet 2017-09-05

$50SAT is Silent but probably still working.
For information on LoRa visit http://www.loratracker.uk/

Grogster

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Posted: 02:47pm 04 Sep 2017

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srnet said For your application LoRa is the way to go, nothing else will come even close to the range. Its not possible to be specific, as environements vary so much but 3km would be trivial for LoRa, you may only need 2dBm\1.6mW for sensor reading applications.[/Quote]

Now I want to know HOW they can get that kind of range, out of that kind of power, on that kind of frequency.

Can anyone link me to anything technical on LoRa so I can have a read?Edited by Grogster 2017-09-06

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yahoo2

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Posted: 05:37pm 04 Sep 2017

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Grogster said
Can anyone link me to anything technical on LoRa so I can have a read?

its basically designed around super low bandwidth and gateways.

You might be better off watching one of Andreas Spiess's videos to get a feel for the big picture first.

#112 LoRa / LoRaWAN De-Mystified / Tutorial

I'm confused, no wait... maybe I'm not...

srnet
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Posted: 08:10pm 04 Sep 2017

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Grogster said

Can anyone link me to anything technical on LoRa so I can have a read?

Why does LoRa cover such long distances?

First of all, understand that quoted data sheet sensitivity for an RF device is as a result of perfect World tests in a laboratory. Unfortunately our RF devices have to work in the real World where there is a lot of RF noise about.

A typical FSK receiver, RFM22B, HC12 etc. will have a data sheet quoted sensitivity of -121dBm or so. With the receiver seeing a typical real world noise level of -100dBm to -105dBm, that would seem to imply that our typical FSK receiver is capable of receiving signals at -121dBm or up to 20dBm below noise level. Thats just not going to happen. Typical FSK devices actually need a positive SNR of between +5dB and +10dB for the receivers to work. In other words these FSK receivers actually need signals of around -90dBm to -95dBm to work, and not the data sheet claim of -121dBm.

The real limiting factor on reception at UHF is the relationship between the signal and the noise level seen by the receiver, i.e. the SNR.

The trick that LoRa pulls is that by using spread spectrum techniques it is capable of receiving signals that are below noise level. Typically -10dBm at 1500bps and -20dBm at 100bps.

So whilst a typical FSK receiver needs a positive SNR of +5dB or more to operate, a LoRa device can work at between -10dB and -20dB, which represents a link budget improvement of between 15dB and 25dB.

A 25dB link budget improvement represents a distance gain of 18 times or so.

$50SAT is Silent but probably still working.
For information on LoRa visit http://www.loratracker.uk/

srnet
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Posted: 08:27pm 04 Sep 2017

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yahoo2 said

Grogster said
Can anyone link me to anything technical on LoRa so I can have a read?

A quite missleading video, taken out of context.

LoRa is a receiver protocol invented by Semtech, its a protocol in the same way that RFM22Bs and HC12s use FSK as a protocol. LoRa can be used point to point in the same way as RFM22Bs, HC12s and nRF24L01 can be. LoRa does not need a 'gateway'.

When compared with our normal FSK UHF devices, RFM22B, HC12, CC1101 etc, LoRa is in fact very wide bandwidth. An FSK device might use a bandwidth (deviation) of 5Khz or so whilst a LoRa device will typically use 40KHz or higher. I use a LoRa bandwidth of 62Khz for my trackers.

LoRaWAN is a wide area networking system that uses LoRa as its base communication technology. Typical bandwidth is 125Khz, but 250Khz or 500KHz can be used.

LoRaWAN is a

$50SAT is Silent but probably still working.
For information on LoRa visit http://www.loratracker.uk/

ryanm
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Joined: 25/09/2015
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Posted: 08:31pm 04 Sep 2017

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I work with radio modules a bit and one thing I would highly recommend is moving to the 915Mhz frequency (still with LoRa modules). 433Mhz has very low output power limits in Aus, which means you can't legally put a better antenna on to get more range. Even if you wanted to break the law since no one is using them (I assume) high gain 433 antennas are pretty rare and expensive.

A second benefit is that 915Mhz is fairly close to Telstra's Next G network in frequency, which means that there are a lot of very cheap antennas on ebay that will work very well.

To get 3km reliable through scrub you would probably be looking at a fairly low data rate of around 200-1000bps with LoRa modules, so I wouldn't intend on a live stream from a RS232 sensor which is more likely 9600bps or higher. You will have to buffer a message, trim off any fat that you can and send periodically.

Hope this helps.

srnet
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Posted: 08:59pm 04 Sep 2017

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ryanm said Even if you wanted to break the law since no one is using them (I assume) high gain 433 antennas are pretty rare and expensive.

High gain 433Mhz antennas are extremly easy to find, they are produced in volume for the nearby Amateur 70CM band which is a Worldwide allocation.

Lots of DIY antenna designs too, again because of their use by radio Amateurs for the 70CM band.

$50SAT is Silent but probably still working.
For information on LoRa visit http://www.loratracker.uk/

srnet
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Posted: 11:21pm 04 Sep 2017

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Wet Forests & Scrubland ?

My evaluation would be that if using LoRa modules (SX1278 etc) @ 433Mhz, the ISM limit of 10dBm/10mW ought to be good for 1000m at 1562bps in a very wet forest. 1562bps is plenty for most sensor applications.

This is based on a test result of -4dBm (0.4mW) being needed to cover 200m through such a forest.

The test transmitter was lying on the ground in the undergrowth, the receiver handheld. You would expect a lot greater range if the transmitter was in a better position.

Details in the 'Lost in a (wet) Forest.pdf' report to be found here;

https://github.com/LoRaTracker/Test-Reports

$50SAT is Silent but probably still working.
For information on LoRa visit http://www.loratracker.uk/

OA47

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Posted: 11:35pm 04 Sep 2017

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Quote To get 3km reliable through scrub you would probably be looking at a fairly low data rate of around 200-1000bps with LoRa modules, so I wouldn't intend on a live stream from a RS232 sensor which is more likely 9600bps or higher. You will have to buffer a message, trim off any fat that you can and send periodically

The field units would be line of sight from the main unit elevated above the crop. My thoughts are that the Micromite would poll the sensor when asked and forward that data back via the radio system to a receiving PC. My worry from the posts that have been made is the running of the console and the associated data throughput from the editor....

srnet
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Posted: 12:19am 05 Sep 2017

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It says that the maximum air rate of those UART 100mW LoRa modules is 19200bps. There is not a 19200bps rate for LoRa, but there is 21875bps, so maybe there are usiung that.

Not done much testing at the higher data rates of LoRa, but in one test using a 5-6dB omni antenna at the reciever end I got 105km @ 13700bps @ 7dBm (7mW), my garden shed to a high altitude balloon.

So if there is line of sight, as you say, I doubt 3km @ 19200bps would stress the capability of LoRa at all.

$50SAT is Silent but probably still working.
For information on LoRa visit http://www.loratracker.uk/

OA47

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Posted: 11:22pm 05 Sep 2017

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Quote High gain 433Mhz antennas are extremly easy to find, they are produced in volume for the nearby Amateur 70CM band which is a Worldwide allocation.

Lots of DIY antenna designs too, again because of their use by radio Amateurs for the 70CM band.

On the subject of antenna, can anyone give me a supplier of 433 MHz 5/8 wavelength, ground independent stainless steel antenna? I am afraid that experience has shown that the bent beak feathered friends find the plastic ones very desirable. I have replaced the 1/4 wave plastics with 477Mhz units but I was thinking I would get better transmission with a longer 433 version.

lew247

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Posted: 11:29pm 05 Sep 2017

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if it's point to point communication with the modules in fixed locations you can make the antenna much better by using a 2 or 3 element beam antenna - 2 pointed at each other will increase the signal strength a hell of a lot, or even one pointed at the other would make a huge increase in gain and distanceEdited by lew247 2017-09-07

srnet
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Posted: 11:46pm 05 Sep 2017

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Whilst there is a lot you can do with antennas, this could well be illegal.

In the UK for instance we can transmit 433Mhz at 10mW licence free. However this is ERP so there is no point at all in using a gain antenna.

For a receiver only, then yes you can use a gain antenna.

$50SAT is Silent but probably still working.
For information on LoRa visit http://www.loratracker.uk/

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