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ryanm
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Posted: 05 September 2017 at 6:31am | IP Logged Quote ryanm

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.


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srnet
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Posted: 05 September 2017 at 6:59am | IP Logged Quote srnet

ryanm wrote:
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.

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srnet
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Posted: 05 September 2017 at 9:21am | IP Logged Quote srnet

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


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OA47
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Posted: 05 September 2017 at 9:35am | IP Logged Quote OA47

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....


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srnet
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Posted: 05 September 2017 at 10:19am | IP Logged Quote srnet

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.

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OA47
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Posted: 06 September 2017 at 9:22am | IP Logged Quote OA47

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.
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lew247
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Posted: 06 September 2017 at 9:29am | IP Logged Quote lew247

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 distance

Edited by lew247 on 06 September 2017 at 9:30am
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srnet
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Posted: 06 September 2017 at 9:46am | IP Logged Quote srnet

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.

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CaptainBoing
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Posted: 09 September 2017 at 9:44am | IP Logged Quote CaptainBoing

interesting link in my news feed this morning:

https://www.thethingsnetwork.org/article/ground-breaking-world-record-lorawan-packet-received-at-702-km-436-miles-distan ce?source=techstories.org

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srnet
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Posted: 09 September 2017 at 10:05am | IP Logged Quote srnet

Indeed and the trackers are very simmple too. The TTN and GPS code will run on a Arduino PRo Mini (1.50).

That report was for 868Mhz too so although they were using 4dB more power than permitted at 434Mhz, the path loss at 434Mhz is 6dB less, implying that the equivalent range on 434Mhz @ 10mW would be 880kM or so.

I once thought of doing a Micromite LoRa tracker.


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OA47
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Posted: 14 September 2017 at 9:31am | IP Logged Quote OA47

I received the LoRa modules yesterday and have come to a brick wall in trying to establish a link between the modules. I believe that they are transmitting as I can see a substantial increase in current draw when I apply data but I don't see any reception either way. The documentation is in Chinglish and shows easily established communications using the supplied configuration and testing apps. I have read through the manual many times but I am still missing a setting somewhere albeit the documentation suggests that they should link up with the default configuration.
Any guidance or suggestions from shedders very welcome.
Graeme
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Posted: 14 September 2017 at 11:07am | IP Logged Quote Grogster

ryanm wrote:
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.


Check your local regulations. I guess this works OK in Australia, but any New Zealand members reading this - according to the data, 915MHz STL's are no longer licensed in NZ, so you CAN use 915-928MHz for LoRA, but stay well clear of the 890-915MHz cellphone band, or RSM and the affected telco will come down on you like a ton of bricks if you mess with their commercial cellphone services.

I'm actually gonna get a couple of the 915MHz version of that module to test on the spectrum analyser to see how they go and to see what their output is like. I was suitably surprised by how clean the HC12's were, so I am hopeful for these ones next.
I will post photos when I do this. The 915-928MHz band in NZ is allowed a reasonably powerful 0 dBW(1W, 1000mW, 30dBm) - starting to be an attractive band for this stuff if you are allowed that kind of power!

EDIT: @ Graeme - Can you post the manual(s) here, or a link to them, and I(and probably others) will take a look and see if we can decipher them. I'm gonna need them anyway for my modules.

Edited by Grogster on 14 September 2017 at 11:11am


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