RPI and long distance radio

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RPI and long distance radio

Post by secs »

Hi all.

Not asking everyone to do the work for me but looking for suggestions from those who may have already played or experimented with various bits and pieces.

I like using Raspberry pi's but at this point that not locked in. More importantly, I need to transmit GPS coordinates between 2 vehicles over a distance of say 3 kilometers. I can use external aerials and wondered if anyone has had success in using any particular radio modules. I would need to transmit say every 10 seconds.

Just looking for feedback on any units you may have tried

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Re: RPI and long distance radio

Post by Jay Dee »

Hi,
I've played with various telemetry systems over the years... 3 miles is actually quite a distance.
It really depends on line of sight (in a RF sence) what is your operating enviroment? If you are in urban or wooded countryside, you'll need quite a rig to get data between two vehicles at 3 mile (5 K).
say an Satel 3AS telemetry modems (458Mhz - UHF) are £1500 and might work but you need to get the recieving antenna up as high as possible, quite a bit more than an local building or tree.

Low cost option for low data rate I would look at a LoRa module from RF solutions. I have run them in countryside with small antenna and achieved 1km reliably. with a true clear line of sight they claim to have reached 16km. Modules are more like £25. You have to send the data via UART to serially send strings but this is limited, I would not go much over 20 characters, LoRa at long distance is pretty slow but amazing at what is can achieve for such low power.
The deal is basically the slower and smaller the amount of data you send, the further you can maintain the link.
J.

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Re: RPI and long distance radio

Post by mnf »

For built up areas, how about a GSM module and send text messages.

Could get pricey (story about eagle flying to Iran and racking up roaming charges.) - but with the right SIM card it could work?

Martin

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Re: RPI and long distance radio

Post by Jay Dee »

Agreed, it was not too hard (ish! :) )to get a simple flowcode setup to send SMS over GSM. You may want to drop your update rate but it does give you almost any range you want.

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Re: RPI and long distance radio

Post by secs »

Thanks everyone.

GSM isnt an option as the units will spend more time where there is no phone coverage. However I think what I will do is use a cheaper rs232 radio module to prove the concept then if the units work ok, simply buy a more expensiveunit...


Thanks everyone

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Re: RPI and long distance radio

Post by secs »

Further to that, I relaised last night that I wont have to send all whole string of gps data but as the units are within a certain distance, most of the string will be the same so I can send only part of the string...... Thus reduce the amount of data

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Re: RPI and long distance radio

Post by AbhijitR »

Hello! Jay Dee
Jay Dee wrote: Low cost option for low data rate I would look at a LoRa module from RF solutions. I have run them in countryside with small antenna and achieved 1km reliably
J.
Actually a couple of years back I tried to work on the same module (GAMMA) from RF Solutions (I am using there other modules since 2008) but unfortunately without success, may be I was wrong or I did not understand how to operate that module.

My first intention was to operate two relays as any other RF module but did not work.

May I request you to help me with this module or how to operate it using RS232 and FC.

Thank you in advance.

Regards
Abhi
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Re: RPI and long distance radio

Post by Jay Dee »

Hi Abhijit,
For long range I used the Lambda module which is LoRa based. I have used the Gamma but only achieved around 100m in our wooded environment (no where near the claimed max distance ), you would get much more in wide open space I expect.

Check the version you have as some are 3.3V and some 5v.
ensure all ground pins are connected.
Use the correct antenna type, as supplied by rf solutions if unsure.
if using for a simple relay control, no connections required for cts, rts, tx,rx pins.

using the Opt pins, set one device as a receiver (only), one as transmitter (only).
using the learn pin, ensure you have the devices 'paired' . if not they will not talk.

even if you don't have a output connected on the receiver, you should see the status light blink if it recieves data.
do a trial transmission from transmitter to reciever, can you get a receive status blink, after a transmission blink from the transmitter?... if not, re-do the learn process.

Note input/output pins are pulled internally high.
Pull to ground to activate an input pin.
Output to a resistor to +Supply, via resistor.
Note: output can only sink 12.5mA so for anything beyond an LED you will need a mosfet or driver chip to activate the relay coil.
all surface mount but I've used infineon TLE6225G & Texas Instruments ULN2003 as relay drivers....but again check the supply voltage and demands of the control pins against what the gamma output pins can supply.
J.

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Re: RPI and long distance radio

Post by AbhijitR »

Hi! Jay Dee

First of all many thanks to write and share your views.
I have used the Gamma but only achieved around 100m in our wooded environment (no where near the claimed max distance ),
To be honest with you, this is the only, more or less range I experienced when I took the trials and unfortunately I kept blaming myself that I was making some mistake to operate the module and wasted app 20-25 days in discussing with the manufacturer.

Okay now if it is clear that GAMMA works only for this range I shall drop the idea on working on it again. If in near future I work again on LoRa module, shall I request you for some pointer on how to operate the module using Rs232 (it is something new for me) if you don't mind. :D

Thank you again for writing.

Regards
Abhi

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Re: RPI and long distance radio

Post by Jay Dee »

Hi, Yes I was also a bit disappointed with the gamma... in wide open space it was much better.

The LoRa Lambda module was much much better... the time to react to the siganls (send/recieve) is a couple of seconds but the range is much farther.
For triggering relays, you can just use the normal Input/output method.
If you want to start adjusting the basic LoRa settings or send strings, you have to use the UART. A bit more involved but achievable.

I started looking at the tiny standalone LoRa modules from RF Solutions, comms is via SPI and you have to deal with all of the register specifics..started working on it (with some help from Ben) but did not get very far. Not a good route unless your very good at reading 100's of pages of semtech documents, wring to each register and detailed debugging! :)
J.

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Re: RPI and long distance radio

Post by chipfryer27 »

Hi

I use the Gamma modules quite regularly and can achieve miles over various terrain just using a standard antenna as supplied by the company. In London I had a Tx on the roof of a four story building bordering the Thames near World's End and could communicate at ground level way past the fire station on King's Road. This is not by any stretch of the imagination "line of site" and would be over one kilometer. Crossing the river I could still communicate at the far end of Battersea park.

In reasonable woods I can still get over a kilometer or so and in open conditions many, many miles (typical Scottish countryside). They are a "go to" module for me as they need very little support.

However you do need to configure them to operate in the required mode. First thing I do is configure all required modules and then if necessary "pair" them as described in a post above. To set the module for maximum power and range, using Terminal (free) send ##C#006#015 to each module in turn after putting it into "learn mode". If using another program such as Putty you might need to omit the first #. Remember to cycle power though (or send reset) to apply changes.

Again, as mentioned in a post above you compromise packet length for distance. At maximum distance it takes just over a second to send each packet. This has never been an issue for me though. I am only ever sending small packets serially or using them in telemetry mode and for that I can highly recommend them.

Regards

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Re: RPI and long distance radio

Post by Jay Dee »

That is indeed interesting... I worked with the Gamma's a few years back and despite the settings changes as advised by RF we managed a patchy 200m around the industrial estate, reliable behavior was at 100m. Talked a lot with RF solutions, ran recommended antennae direct from the module etc.. RF solutions eventual conclusion was ..." well it all depends on terrain" so we had to abandon that route after a few weeks dev.
We did not have height... both units at ground level and with radio RF the one golden rule is 'Height is King' so maybe that was the big issue we had. The Lambda units however, might be a bit slower but punch through everything locally.
Can only speak from experience but low power, low level conventional radio modules rarely achieve anything near stated distance in application.
J. :)

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Re: RPI and long distance radio

Post by LeighM »

Thanks guys, this is an interesting read. These real life experiences are valuable.
Last time I attempted RF data comms was within castles, no chance! :lol:
Ps. Drilling holes through walls for cables ain’t allowed :roll:

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Re: RPI and long distance radio

Post by AbhijitR »

Hello! Chipfryer27
chipfryer27 wrote: To set the module for maximum power and range, using Terminal (free) send ##C#006#015 to each module
Thank you for taking time to share your views, with success :) , but unfortunately for me without success. Even I was provided with some settings (in attachment) by the technical person (Mr. Simon ANSCOMBE) but it did not work, or may be I did something wrong, may I request you to check if this makes sense, I think it is different from the one you mentioned above.


Hello! Jay Dee
We did not have height... both units at ground level and with radio RF the one golden rule is 'Height is King' so maybe that was the big issue we had.
Even I had this thought, that may be height will improve the range, so I installed the transmitter on top of a building (app 30 meters) but still no success.

I still want to use that module, hope I find some answer, I am regularly using the other RF modules from RF solutions and I am very happy with there performance but GAMMA did not worked, if I was wrong I am still in the game :D

Thank you again.

Regards
Abhi
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Re: RPI and long distance radio

Post by Jay Dee »

Hi,
sorry can only give basic support on this as customer is bashing me to sort other projects! ... who needs customers!
the Gamma is OFDM not Lora so sorry about the file name.
I'm pretty sure this was a working Gamma testing FlowCode.
LoRa_Test_GAMMA_Program1.fcfx
(35.16 KiB) Downloaded 167 times
from a quick look, i noticed a few things.
A) this was a rough hack to test the gamma...so its crude!
B) if you dont hold the first button (btnHW_Setup) during power on it will jump to a loop that pulses one of the inputs...a simple transmit test
C) if you get into the packet setup menu, it assumes the use will manually press and hold the learn button to push the Gamma module into Learn Mode ( flashing status LED)
C) the main then just looks at switches, based on that sending serial string to the Gamma via the UART.
D) Other macros send different strings for setting up different jobs.. I think you have to ru the Reset string to 'set' any changes.
E) there is no exit from the Learn Loop that I can see, you power cycle the device and it should default to the transmit mode.

I think ...I think!! I had this all working.
Obviously you have to have the same settings in receive and transmit.
In my Lamda version I automated the Learn Switch and tidied everything else up but this may be a starting point.
I'm just a bit pushed to go back through it all again at this time, sorry. J.

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Re: RPI and long distance radio

Post by chipfryer27 »

Hi all

Traveling as usual so apologies for tardy reply.

I haven't used the Lambda modules but they do sound like another good product. I agree that terrain, height and castle walls will all affect your success with any radio module (as an aside I once had to rely on PLC for a castle as you couldn't just cable).

My first play with the Gamma's wasn't too impressive (four years ago perhaps). I "configured" for maximum distance and power then went to play. They have a test facility which allows you to do range testing with little in the way of support, but I just had them in Transceiver Mode with "Feedback". In this setup if I change state on an input on the local unit, it will transmit such to remote unit. If the remote receives it will then change state of a different input and this will then be transmitted back to my local unit (e.g. If I change state of input 1 and the remote unit receives it, it will change the state of my output 1). Basically I had as each unit a battery, an LED or two, a Gamma and a button on the Tx.

Using the standard antennas off I went for a walk around the houses. The Rx unit was located in an upstairs bedroom of a typical two story house which in one direction faces typical fields and on the other more housing. I could communicate perhaps 200m at best when walking into the streets (with a few houses blocking direct LOS to the receiving house) but nowhere near my hoped for range when in the fields.

The documentation (at that time) was a little confusing in places and it transpires that I was not configuring correctly. Once resolved I was and still am impressed. My latest test involved setting up a Tx unit (with a PIC) to increment a counter then transmit this value every twenty seconds. The Rx unit would display the last value received. If comms was good I would see the counter increment every twenty seconds. If I entered a black spot, when I exited and regained comms I would see the counter jump from say 45 to 53 which gave me an idea of the location and distance of the black spot.

With the Tx unit mounted around chest height to a tree in the local woods, I went for a walk. The woods are maybe a couple of hundred meters in diameter. Within the woods I had very reliable comms so went for a drive. All good with the usual expected black spots as the road dipped but I could still communicate down at the beach which is at the other side of the town from the woods (same at the golf course). I was hugely impressed especially as the Rx unit was inside a van using a simple antenna. I won't pretend that there were no areas where I lost comms but driving a few tens of meters would usually resolve (with obvious exceptions). If anyone is bored at work and interested in the results I obtained, you could look up Google Maps or the like and find Troon in Ayrshire. The Tx unit was placed in Fullarton Woods facing East near Eastern edge (close to Rugby ground). Comms was reasonably maintained whilst driving to the rear of Dundonald hill (lost on route approximately half way). Once cresting the hill comms was regained and pretty much maintained down to North Beach, then through town to Royal Troon golf course. This exceeded my needs by a long chalk and I again reiterate I did have some black spots but it is still impressive to me.

In Wales I used PICs and a few Gammas to monitor water tanks fed from a spring. The Gammas and a very basic PIC slept in each monitor until triggered. They would then send a status change to the Rx PIC/Gamma inside the house. That PIC would attempt to communicate via the broadband and ultimately send me an email / Push notification. If for whatever reason it couldn't communicate via the internet an audible alert would sound. The units would on average send an alert every month or so. I've just recently changed the batteries in the Tx units after over three years of use. The cottage walls are up to three feet thick in places (typical construction techniques in late 1600's with absolutely no consideration given during such for RF issues. Most castle builders didn't care either <s>) with lower tank approx 80m away out of direct sight and the upper tank around 30m away in direct view of the cottage but at far end from receiver.

Testing with a Tx unit placed outside an upper story bedroom window gave great results over many miles of typical countryside and I have no doubt that they can do as claimed in direct LOS (16Km). Incidentally RF inform that that range was achieved using a very basic setup similar to that above using standard antenna.

I may just be very fortunate as I have the benefit of height in London (reflections can be a good thing <s>) and countryside when deploying but they really are a "go to" unit that I highly recommend. RF Solutions customer service is also to be highly commended. I found a "bug" that was, depending on use, causing me concern. They posted out new units that resolved the issue FOC despite my units not being of the latest version (and possibly out of warranty too).

None of the above I could have done without Flowcode and of course the excellent support from Matrix and forum members (big thanks to all).

I've looked at Abhi's attachment and initially the comms settings to communicate with modules look OK especially as there is an "OK" response. However I very much favour setting Terminal to display Hex rather than ascii as it is far easier to read config strings which let you know what's really happening. I'm traveling but I should / hope to be back at the weekend and if still needed I will forward my settings / configs etc that get me working. Sorry I can't be of further help at this time but you know how annoyed security staff get if you pull out a bunch of electronics whilst waiting to board especially if there is a big LED display counting. I really should leave my programmer and combo board behind :)

Regards

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Re: RPI and long distance radio

Post by AbhijitR »

Hi! Jay Dee

Many thanks to share the chart, I shall give a try once I finish my assignment, which is getting delayed due to some changes in the chart from the customer,
... who needs customers!
:evil:

Hello! Chipfryer27

It seams you have a pretty good experience with LoRa modules, I am happy to hear that.
None of the above I could have done without Flowcode and of course the excellent support from Matrix and forum members (big thanks to all).
As you said, I do agree with you, since my purchase of FC6 in 2014, I began/started to learn PIC chips and eventually use those in my professional life, I was never successful in learning 'C' language to write the programs for PIC, I am so lucky that I reached MATRIX and happy to use FC. I spend quality time in writing the logic and the chart do the rest.

I have used FC to program PIC chips along with RF Solution's, RF modules, 3 times in a project to operate a train of hangers which carry the chassis of the car in the paint shop of Mercedes-Benz in Pune (my home town) and in Russia too, I am aware of the quality and performance of the modules but unfortunately the GAMMA did not work, or may be I am wrong to use it.

kindly excuse for the confusion, the attachment in the previous post was not mine screen short but the one shared by the technician of RF Sol, I have attached mine in this post. If you are interested I have also attached the Remote/Receiver of MB.

Thank you again to both of you to take time and share your experience.

Regards
Abhi
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LoRa Settings by Abhi.png
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Re: RPI and long distance radio

Post by chipfryer27 »

Hi Abhi

Very professional looking modules you have there. I'll be very jealous if you made it all by hand :)

I've been in Pune a few times but not for many years now (visiting a NOC) and always enjoy my trips to India. Chicken 65 from Cochin is possibly my all time favourite food (well, perhaps pineapple curry in Borneo maybe just tops it).

I'm on route back now and over the weekend I'll document the settings that seem to work well for me and post. My antenna / enclosures are very similar to yours (but without the cool boards inside).

Late last year I had to create a network of sensors reporting back to a Receiver which would entail deployment of the sensors in woods / estates. Range was a worry in the woods so a "mesh" was created with sensors relaying. Many a fun night with Flowcode creating that code. Good job there is never anything on TV :) In practice we found that the current draw meant batteries (2 x "D" cells) would only last about six weeks or so which wasn't good, especially as only a few units were out of range. A very cheap solution was to get rid of the "mesh" and then move the Rx antenna higher. Rather than expensive co-ax runs I simply put the Gamma unit itself in a waterproof enclosure and used standard multicore cable (Cat5e if I remember) to connect the external Gamma unit to the indoor Rx unit. Now the Tx units run on 2 x "AA" cells and as they draw under 10uA unless transmitting, battery life is no concern.

Regards

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Re: RPI and long distance radio

Post by chipfryer27 »

Hi

As promised, my settings. I took an existing module and gave it a factory reset by holding the Learn button for over ten seconds.

I prefer to just use some breadboard and jumpers whilst configuring and usually keep the pins associated with RTS/CTS free. If not using a regulated version then power should not exceed +3.6V. I use a generic USB to Serial convertor and run Terminal to communicate.

Gamma Connections
Pins 2 and 15 = Ground
Pin 16 = Positive
Pins 17 and 18 = Serial Rx/Tx

My Terminal settings
Settings.JPG
Settings.JPG (60.22 KiB) Viewed 11915 times
To retrieve the current Gamma setup send a status request of a hash followed by a question mark (#?) Note if using Terminal and you want to use the # character in your Macro you need to type it twice.

Sending Status Request
Capture1.JPG
Capture1.JPG (92.34 KiB) Viewed 11915 times
We can see in the above that I typed ##? then clicked send which sent #?
The Gamma responded with an eleven byte reply (preceded by an echo #?) 23 3F 7F 7F 7F 7F 7F 7F 01 05 0F 00 00
23 3F = hex value of #?
The first three bytes 7F 7F 7F are the local module address
The next three bytes 7F 7F 7F are the destination module address
Byte seven, 01 is a null value
Byte eight, 05 is the LoRa Mode and this sets the packet length 01 = 55mS with 05 being 720mS and 06 being 1.02S
Byte nine, 0F is the output power between +5 and +20dbm (00=+5, 01=+6..0F=+20)
Byte ten, 00 is Handshaking Mode
Byte eleven, 00 is Baud Rate

To set the module for greatest range we want the longest packet length and highest power. To do that we will send ##C006#015
Capture2.JPG
Capture2.JPG (93.55 KiB) Viewed 11915 times
We can see in the above after sending our command the module responded with 4F 4B which is the hex equivalent of "OK"

Due to what I think is message size limitations we will follow on in my next post.

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Re: RPI and long distance radio

Post by chipfryer27 »

Following on from previous.

If we send another status request we can see the changes
Capture3.JPG
Capture3.JPG (93.71 KiB) Viewed 11915 times
Bytes eight and nine are now 06 and 0F respectively which is LoRa Mode 6 with an Output Power of +20dbm

To apply these changes we need to either cycle power or send a reset command #Q
Capture4.JPG
Capture4.JPG (95.61 KiB) Viewed 11915 times
That's it, the module can now be set for whatever application you wish such as telemetry or modem by setting pins 10 and 14 appropriately. I usually have a PIC with some Flowcode magic inside and in modem mode I can send messages with a typical length of 12 bytes between modules miles apart.

I hope the above helps and I'd be very interested to hear how people get on with ranges in their applications.
Regards

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Re: RPI and long distance radio

Post by AbhijitR »

Oh! Dear
I've been in Pune a few times but not for many years now (visiting a NOC) and always enjoy my trips to India. Chicken 65 from Cochin is possibly my all time favourite food (well, perhaps pineapple curry in Borneo maybe just tops it).
what a pleasant surprise, in which part of the city did you visit, let me guess, Koregaon Park/Kalyani nagar, is it? I welcome you back to Pune to enjoy your favorite food :) I stay in the north part of the city, more or less near the Industrial zone. Do update me if you visit again.

I am deeply touched for all the efforts you took for making the GAMMA topic so easy to understand for me, I am sure I will be able to work with success this time, once I am done with the present assignment (probably by the end of the coming week) I shall take all the stuff out of the box and give a try I am sure to see some results from this module (GAMMA) now.
Very professional looking modules you have there. I'll be very jealous if you made it all by hand :)
Thank you for the compliment, yes indeed the designing work of the PCB is done by me, the remote PCB is soldered by hand but the receiver PCB (9 quantity) was soldered on wave solder machine.

Once again many thanks for all the efforts and your valuable time, I shall keep you posted, have a nice weekend.

Regards
Abhi
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Re: RPI and long distance radio

Post by chipfryer27 »

Hi Abhi

Always happy to provide whatever help I can. I always have a few Gamma's kicking around so if you or anyone get strange results or the like, I'd be happy to see if I can replicate.

Getting back to secs original and follow up posts, you will be operating in an area without GSM and will be transmitting GPS coordinates. How critical is it that every transmission gets through? Each vehicle is exchanging their location every ten seconds, but what would be the penalty if they went dark for a few transmissions or so? I ask as whilst you can guarantee communications if you have the correct budget and conditions, emphasis on budget, it may not be practical or actually required in "real world". With no GSM it suggests open countryside rather than built up city.

My experience with the Gamma's allows me to have one in a fixed location communicating quite reliably whilst inside a moving vehicle (no external antenna), so I think it would be worth exploring their use, especially as the are very cost effective.

Regards

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Re: RPI and long distance radio

Post by chipfryer27 »

PS
Forgot to state the obvious that you need to be in "Learn" mode to do any of the above. Easiest way is to press and hold the "learn" button for two seconds or so until the onboard LED starts flashing

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Re: RPI and long distance radio

Post by AbhijitR »

Hello! Chipfryer27

Following your post and all the instructions I tried to read the data from the GAMMA module, but unfortunately without success. As you said the terminal program gets connected to module, I type ##? and send, I see #? in the bottom line, but nothing returns back from the module.

I am using the FTDI232 (USB to serial PCB) and set for voltage 3.3V, again clueless do not understand why the module do not respond, yes I have pressed the learn button and the green LED is flashing too. Below is the picture for your knowledge.

Thank you.

Regards
Abhi
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Hokum52
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Re: RPI and long distance radio

Post by Hokum52 »

So, if I got things right, it's advancing slowly but surely, right? The thing is that I'm interested in the cooperation of the Raspberry Pi with radios, as I'm working on a hobby project based on this (a remote control all-terrain vehicle with a camera) that I'll use in the little bit of this Portugal real estate I'm getting for the holidays; fortunately enough, it won't be too covered by vegetation, so that's one less source of connection problems.

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