2 watt RF (33dBm) amplifier range test

I will be testing a 2 watt amplifier booster attached to a TTGO, Two TTGO will use a 2 watt booster to see what kind of range I can get in a city environment. The unit I have has a frequency range for 1- 930Mhz. I may go to a 6 watt later after testing this one . In an emergency I want to make sure if i use this device it gets to who i need to communicate with . There can be no maybe or I don’t know . if i use it it has to work or what is the point. My partner on March 2 and she will be using the other TTGO. I am also thinking about setting up an antenna mast and making a water tight enclosure and running power up to the device. SO there will be a few high power test I am going to do.

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Keep in mind, antenna efficiency and height are generally more important than power output and that depending on where you are located output power and perhaps duty cycle are limited by law because the spectrum is shared.

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I’m interested in just how much it helps.

Please do tell us if you get a visit from someone because every time you transmit everything that uses that frequency within a mile stops working.

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I fully agree with @scottbridges to improve the range of a radio setup good practice would be to start with antenna improvement , well that is what I have learned getting my Ham Radio license I always saw and still see it as a challenge to get a good range with minimum pwr , a well tuned antenna is far more effective and actually a bad tuned antenna does no good to the power input ratio resulting in loss and efficiency of the transmitted signal and all other unwanted side affects, link below explains all this:
https://n6pet.com/power-loss-various-swr/

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FCC regulations heavily promote higher gain antennas over higher wattage amplifiers. More focus (higher gain) means you only pump out RF directly at your target rather than at everybody in the area. It also means you only listen at your target rather than at everybody. Think cupping your hands over your mouth & ears when trying to speak/listen to somebody. RF is a shared spectrum & just pumping up the volume pollutes the spectrum more for others.

Focused directional antennas are definitely harder to aim & aren’t always compatible with mesh topology fundamentally. But it’s good to think about.

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I strongly agree with all of the comments on this. First of all, the 902 to 928mhz radio spectrum is in the ISM band. That is Industrial, Scientific and Medical. If you are in the city which looks like you are, there is a lot of traffic on this band, especially in the medical field. What you propose to do will potentially cause interference to these devices in which case you may well receive a visit from some less than friendly individuals ( I had to track down interference once in regards to control type devices in that spectrum) Second, you would need to make sure that the amplifier used would be compatible with the lora modulation scheme, and most likely it is not. Although the band is also part of the amateur radio spectrum,even if you have a ham license you cannot run this type of equipment under that license as encryption as well as modulation method is not permitted, which leaves you with using it unlicensed and with a power limit. My concern is not only for your own legal protection but also for everyone else that uses these devices on the spectruim. All it would take is for some abuse of the rules for the F.C.C. to remove approval of these devices from the spectrum and leave everyone without the use of this awesome device. Antenna is about the best you could do to improve your signal without incuring potential legal issues and potentially making things difficult for the rest of the users on here. Just my two cents worth.

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Thanks for the great post and welcome to the community.

Unfortunately some people are stuck on trying to push limits. This is not the first time a topic like this has come up here.

There are settings that you can change first, special channel settings will effectively double the range and set the radio to expect the delay that comes with that. Getting well over 5km with stock atenna and chaging radio settings. Mc Hamster has a post about custom channel settings that so far has made a big difference in range.

LoRa reccord that I know of using a balloon is 450 miles with a simple atenna so its more the settings thats matter.

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The problem with all this is with all the legal mumbo jumbo and letting me know about the laws… I live in the city YES… I plan on using it in an EMERGENCY situation ONLY like if all the power goes out . Black out or what ever disaster happens. I doubt it greatly that anyone will be looking for me with legal issues. What I am after is that through all the things in the way like buildings or what ever , I want to be in contact with certain individuals. SO its for emergency situations only. So any legal advise posted is not what this topic is about. When the s**t hits the fans at least I plan on still communicating with very important individuals. There will be no looking to see if I broke any laws. There is also something else that I am going to do but I will test that before I mention it. I will post results when my partner GETs here as she is still NOT here yet . So I have delays. Thanks for any feed back gentlemen.

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Meshtastic-device/radio-settings.md at master · meshtastic/Meshtastic-device (github.com)

meshtastic --setchan spread_factor 12 --setchan coding_rate 8 --setchan bandwidth 31

These settings will set the radio to an insane range keeping it within limits, there is no need to boost the signal DB as range and delay are a function of each other in LoRa so it takes a long time but these settings get insane ranges. Line of sight 30km+ no problem. I think someone has gotten 75km with these settings so it is more about tuning the radio than trying to boost the signal. LoRa works because it is able to be detected with a lot of background noise so distance is not the issue, latency is. In my test, it took over 8 minutes for a message to go 30km but it did go and it works with the stock antenna and power settings.

When in a city it doesn’t matter how much you boost as the signal is going to get blocked by buildings most of the time, having a high elevation repeater is more effective than a lounder signal. This could be achieved with a balloon or being on the roof of a tall building.

Balloons less than 6lbs (including payload) , 6 ft across, and tethered with cordage that breaks at 50lbs and you have a Meshbaloon that is legal to launch tethered. Launching things in the sky is a real quick way to get in trouble though so make sure you check you local laws. You can make a shit hits the fan system that is legal to test and falls within guidelines so that the project doesn’t end up pissing the wrong people off.

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Are those 3 settings supposed to be in the QR code? I have a custom channel and ran the command but the QR code I gave to a friend looks the same. It seems the only way to generate a random encryption key from the app is to change the name of the channel. It would be nice to be able to add --setchan psk random to that line

no I think they adjust the radio not the channel you would apply these settings to the radios you want to communicate at long ranges

Hmm it would be a nice addition to make it part of the channel, since you would need the same settings to communicate anyway. That way everyone doesn’t have to use the cli. I’m hoping these settings may allow me to reach 5km in the city, so far the default settings don’t seem to be able to reach and I don’t have access to any rooftops.

There are to many settings that different people need that it has its own dedicated setting, its one of the reasons I made the Meshtastic-PyGUI so that adjusting these is easy. I plan an being able to allow users to save config profiles so they can apply settings to mutiple radios easier. We will aslo be able to test save and share profiles with each other to figure out the best setting to get the max range.

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Yes I agree, it would be nice to have a dedicated setting too in the app, but I still think that there’s not much reason to share a channel qr code if you don’t intend on using the same radio parameters, so it would be a huge convenience win. If these parameters were exposed in the app, then if someone really wanted to join a channel then change the parameters, they could do so after they scan the qr code.

At the very least I think the qr code should carry the info but prompt the user scanning it if they also want to apply the same spread factor, coding rate, and bandwidth settings.

This will install the Desktop GUI

Windows:
python -m pip install --upgrade meshtastic-pygui

MacOS:
pip3 install --upgrade meshtastic-pygui

to launch

python -m meshtastic_pygui

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Blockquote

This is certainly a far better approach,I had similar results with nearly the same settings, my settings where SF12BW125DR5 when I was testing a Lora GPS Tracker in the field, please take a look at pictures below, the Gateways that where far away from my original positions and able to receive my Lora signal had considerable heights so this exactly reflects what @zebus is trying to explain.
2020-07-10 13:40:22
Node: marktrackgps
Received by gateway: is Gateway Nieuwe Tonge
A840411E96684150
Location accuracy: 0.00
Packet id: 180698642
RSSI: -125.00dBm
SNR: -12.20dB
Signal: -137.2dBm
DR: SF10BW125
Distance: 4014m
Altitude: -18.0m

2020-07-06 13:43:36.925122+00
Node: marktrackgps
Received by gateway: is Gateway Goes
FCC23DFFFE0AA6E3
Location accuracy: null
Packet id: 3818992
RSSI: -118.00dBm
SNR: -13.50dB
Signal: -131.5dBm
DR: SF12BW125
Distance: 27127m
Altitude: -18.0m

@mnemonics101

What is the reason to build your amplified setup? Do you assume the standard pwr of your board is not sufficient? Have you done some range tests already? Did you look at alternative possibilities to get in touch with your important contacts? Are you aware that in case of an emergency there are other possibilities that might even be more suitable or efficient for your requirements?
Are you fully aware what the consequences can be for you personal but also not to forget other users of the Radio Spectrum IE existing Emergency Services?
Are those important people you mention working for Emergency Services?, do they have a vital role?
I am just wondering what you have done in general research to go down this route.
Is your Emergency scenario really an Emergency or do you just want to be able to get in touch with your important contacts in case of a possible Blackout to check of they are still ok and what they are going to have for dinner.
Please don’t get me wrong, I am not judging you, my apologies if it comes over that way,this is not my intention at all.

Cheers

Mark

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That was me for the 75kms I was using standard very long range but slow using the SX1262 on a tbeam

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If you want something to work during an emergency, you need to test & train with it during normal times. I fully understand only looking out for your tribe when things go badly. But you need to prepare for those times now. And that would mean testing your setup dumping out illegal levels of power now.

The number of times I’ve setup radio or IT gear & KNOWN I did it right or had the right gear yet it still failed to work is uncountable.

If you want to go high power, HAM radio & the APRS system for text does exactly that legally. Gear is a little more expensive & you both need your easy to get HAM radio license. But you can run over 100 watts if you want, up to 1,500 watts on some bands.

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I think I’ve mentioned this else where but think it is worth repeating.

I believe a productive path forward for those seeking longer range by using more transmit power is using the HAM options and getting the 1 watt radio modules working.

We are not the radio police, we aren’t checking to see if call signs are valid, or if encryption is actually turned off, or if you are using the devices for commercial service.

Personally I feel better helping people that try and play nice on the shared radio spectrum.

If enough people are interested how about we organize a HAM club and help each other get licensed.

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