Off Grid Digital COMMS Discussion

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  • dblas

    Past President, MSI
    MDS Supporter
    Apr 6, 2011
    13,087
    FWIW: On grid communications can be made fairly secure with GPG/PGP ( https://gnupg.org/ ). The 4096 bit key is pretty secure and will keep most folks out of your business. Using encrypted messaging on the Internet may raise eyebrows though.

    Encryption is the norm in many college/educational email accounts ( .edu ). Less chance of being singled out on encryption here. You can get an account at many colleges by just requesting an application to the school, although you may have to pay a fee.

    Encryption of information is an entirely different topic from performing digital communications (In this case SMS) without a grid.
     

    dblas

    Past President, MSI
    MDS Supporter
    Apr 6, 2011
    13,087
    Any idea what the effective range is of a single transmission with no hops? I only need a few blocks, say maybe .5-.75 miles.

    900 GSM should be fine for that, if you want to test it get a couple of old Nextel push to talk phones, make sure they have a sim and use them for 900 GSM walkies. No, they do not need to be subscribed to a carrier for the push to talk to work.
     

    mac1_131

    MSI Executive Member
    MDS Supporter
    Jan 31, 2009
    3,280
    Any idea what the effective range is of a single transmission with no hops? I only need a few blocks, say maybe .5-.75 miles.
    that's the elephant in the room.

    VHF 1200 baud (or even 9600 baud) packet is agonizingly slow. There used to be a lot of packet BBS on ham radio but mostly they are gone now too, with some exceptions. The 1200 baud becomes even less with all the store and forwarding going on, it is nowhere near 1200 baud.

    And other low power VHF or even above technologies are pretty much unobstructed line of sight. So you might get a mile or half a mile if your terrain is completely unobstructed, which isn't usually the case.

    Fast forward to newer broadband technology, becoming available and cheap, some uses ham radio spectrum and some uses unlicensed spectrum. This gear uses microwave frequencies which are even more point-to-point meaning you need tower sites to link your backbone together to have anything meaningful.

    There is no free lunch here, unfortunately. Some of us prepper types have formed our own localized ham radio nets where we have practiced and can communicate over various distances, but it is completely in the clear as ham radio regulations prohibit encryption so you never know who is listening.
     

    ToolAA

    Ultimate Member
    MDS Supporter
    Jun 17, 2016
    10,499
    God's Country
    Any idea what the effective range is of a single transmission with no hops? I only need a few blocks, say maybe .5-.75 miles.


    I have tested this in my own neighborhood and range varies depending on the surrounding terrain. I placed one unit sitting on a shelf in the master bathroom which is on the second floor. I was able to communicate with it probably .9 mile away but only from the east which is downhill. From the west and north could reach the end of my neighborhood probably about .4 miles, rough guess.

    That being said, I have been thinking about trying out the idea of tethering one of these to a kite or large mylar helium ballon and then getting it aloft 200-300 ft above my house. That should greatly extend the line of sight range.

    If you want to try these out sometime. I don’t mind lending them to you. Just msg me.
     

    ToolAA

    Ultimate Member
    MDS Supporter
    Jun 17, 2016
    10,499
    God's Country
    that's the elephant in the room.

    VHF 1200 baud (or even 9600 baud) packet is agonizingly slow. There used to be a lot of packet BBS on ham radio but mostly they are gone now too, with some exceptions. The 1200 baud becomes even less with all the store and forwarding going on, it is nowhere near 1200 baud.

    And other low power VHF or even above technologies are pretty much unobstructed line of sight. So you might get a mile or half a mile if your terrain is completely unobstructed, which isn't usually the case.

    Fast forward to newer broadband technology, becoming available and cheap, some uses ham radio spectrum and some uses unlicensed spectrum. This gear uses microwave frequencies which are even more point-to-point meaning you need tower sites to link your backbone together to have anything meaningful.

    There is no free lunch here, unfortunately. Some of us prepper types have formed our own localized ham radio nets where we have practiced and can communicate over various distances, but it is completely in the clear as ham radio regulations prohibit encryption so you never know who is listening.


    I was hoping you would chime in. I know you have some experience in this arena. Are you familiar with LoRa and LoRaWan? It seems like the technology operates on the old GSM 900mhz band. From what I’m reading people can reach several miles even obstructed but the transmission bandwidth is very small. Not really a problem for short SMS messages though.
     

    cantstop

    Pentultimate Member
    MDS Supporter
    Aug 10, 2012
    8,158
    MD
    Encryption of information is an entirely different topic from performing digital communications (In this case SMS) without a grid.

    Yeah. I guess I don't understand. If you are relying on a cell phone for "off grid" SMS comms and the cell network is still up, your provider could brick your phone on bootup and perhaps even sooner.
     

    swamplynx

    Active Member
    MDS Supporter
    Jul 28, 2014
    678
    DC
    I have tested this in my own neighborhood and range varies depending on the surrounding terrain. I placed one unit sitting on a shelf in the master bathroom which is on the second floor. I was able to communicate with it probably .9 mile away but only from the east which is downhill. From the west and north could reach the end of my neighborhood probably about .4 miles, rough guess.

    That being said, I have been thinking about trying out the idea of tethering one of these to a kite or large mylar helium ballon and then getting it aloft 200-300 ft above my house. That should greatly extend the line of sight range.

    If you want to try these out sometime. I don’t mind lending them to you. Just msg me.

    Love the balloon idea. I’ve also thought of ripping one apart, soldering a BNC connector to the board, and dropping it into waterproof kit box with a high gain antenna on top. I’d mount it to an existing mast on my roof, and power would be easy to run, or USB solar would likely keep it topped off too.

    I don’t believe their are any FCC emitter height restrictions for 900 ISM and even with a 6dBi antenna you should still be well under 1W.

    The biggest bitch is the way the relay mode in the GoTenna is activated. You have to hold down the power button, and if it looses power, it doesn’t return to the same state. I don’t want to have to climb on my roof every time it power cycles.

    If you head over to the GoTenna forums, there are a lot of interesting ideas...
     

    bikerbankr

    Active Member
    Mar 1, 2010
    393
    Upperco, MD
    Love the balloon idea. I’ve also thought of ripping one apart, soldering a BNC connector to the board, and dropping it into waterproof kit box with a high gain antenna on top. I’d mount it to an existing mast on my roof, and power would be easy to run, or USB solar would likely keep it topped off too.

    I don’t believe their are any FCC emitter height restrictions for 900 ISM and even with a 6dBi antenna you should still be well under 1W.

    The biggest bitch is the way the relay mode in the GoTenna is activated. You have to hold down the power button, and if it looses power, it doesn’t return to the same state. I don’t want to have to climb on my roof every time it power cycles.

    If you head over to the GoTenna forums, there are a lot of interesting ideas...

    If you're ripping it open to solder in a BNC connector, why not solder in some wire for a remote power button and power source as well?
     

    ToolAA

    Ultimate Member
    MDS Supporter
    Jun 17, 2016
    10,499
    God's Country
    I am referring to radio to radio, and NO, you do not need to a license to run APRS on other services. Since SMS/data type services are permitted on MURS and GMRS, so to is APRS and the messager part of the service. The best part is an actual repeater (Two radios, two frequencies) isn't needed, as a simple digipeater in an ammo can will suffice, set up a radio running APRS and program as a digi at everyone's house, put up a decent, unobtrusive antenna and have an APRS network, sans internet.


    I thought digital communications on MURS or GPS frequencies are limited to 1 second maximum transmission length. How do you setup a “network” without continuous transmission? Also to transmit GMRS frequencies using APRS do all operators require a GMRS license or is the device itself Part certified?

    I would love to see more detailed info on this setup. Do you have any links or videos to share?
     

    ToolAA

    Ultimate Member
    MDS Supporter
    Jun 17, 2016
    10,499
    God's Country
    If you're ripping it open to solder in a BNC connector, why not solder in some wire for a remote power button and power source as well?


    I’m just beginning to dabble in Arduino and it seems like it would be extremely easy to add a small Seeeduino which is about the size of a Nickel to automatically “press” this button at power every power up cycle.
     

    dblas

    Past President, MSI
    MDS Supporter
    Apr 6, 2011
    13,087
    I thought digital communications on MURS or GPS frequencies are limited to 1 second maximum transmission length. How do you setup a “network” without continuous transmission? Also to transmit GMRS frequencies using APRS do all operators require a GMRS license or is the device itself Part certified?

    I would love to see more detailed info on this setup. Do you have any links or videos to share?

    Yes, all users need to be covered by a GMRS license.

    No, a radio does not need to be transmitting continuously. APRS is transmit as needed, you type the message, you hit enter, it transmits. The digi (all of them that hear you) receive it, and then re-transmit it. Same as a digi for packet, your radio isn't transmitting all of the time, only when sending info, the digi listens and then resends what it hears on to the next digi or station. The different is, with APRS you don't need to know the callsign of the digi, but you do need to include the number of hops in the address header.

    Bob Bruniga has a bunch of videos on this, it was the largest thing he kept hyping as he created and refined APRS.
     

    ToolAA

    Ultimate Member
    MDS Supporter
    Jun 17, 2016
    10,499
    God's Country
    Yes, all users need to be covered by a GMRS license.

    No, a radio does not need to be transmitting continuously. APRS is transmit as needed, you type the message, you hit enter, it transmits. The digi (all of them that hear you) receive it, and then re-transmit it. Same as a digi for packet, your radio isn't transmitting all of the time, only when sending info, the digi listens and then resends what it hears on to the next digi or station. The different is, with APRS you don't need to know the callsign of the digi, but you do need to include the number of hops in the address header.

    Bob Bruniga has a bunch of videos on this, it was the largest thing he kept hyping as he created and refined APRS.


    So if someone has a GPRS repeater can you pass APRS traffic through the repeater? Do you need more than a GMRS license to setup your own repeater. I mean in Norton’s use case he is just trying to cover a roughly 500yd diameter. I suspect he could do that with just a 5 watt handheld and a $20 antenna. He could probably buy a 50watt mobile rig and a $150 antenna on the roof and easily cover 2-5mi radius terrain permitting.
     

    dblas

    Past President, MSI
    MDS Supporter
    Apr 6, 2011
    13,087
    So if someone has a GPRS repeater can you pass APRS traffic through the repeater? Do you need more than a GMRS license to setup your own repeater. I mean in Norton’s use case he is just trying to cover a roughly 500yd diameter. I suspect he could do that with just a 5 watt handheld and a $20 antenna. He could probably buy a 50watt mobile rig and a $150 antenna on the roof and easily cover 2-5mi radius terrain permitting.

    Will packet pass through a regular repeater?

    Yes, you need a GMRS license to set-up and transmit on any GMRS frequencies, repeaters included, it's the same as amateur radio.

    A mobile and an antenna set up as a digi at his house and 5watt radios for the area he is covering would be more than enough, 25 watts and a j-pole would get you further than 5 miles.
     

    Antarctica

    YEEEEEHAWWW!!!!
    MDS Supporter
    Sep 29, 2012
    1,728
    Southern Anne Arundel
    A number of months ago I posted in the amateur FAQ thread (central region forum) a bit about the Aredn system. This is a mesh network that has been developed mostly out west. It is TCP IP based and is frankly axactly why is needed, and I was interested in it for a grid down comms network. I set up two nodes, but the system is pointless without others participating. They use some really nice commercial nodes.

    If you read about it, it is a really interesting system. Its built on mesh nodes, so if one goes down, the whole system doesn't go down. While mesh nodes (ham or not) are a fantastic idea, they have their issues with high overhead, and nothing works well without decent node density. The problems aron the east coast are compounded by:

    1) Lack of high sites/topography
    2) Foliage.

    Nonethleless, its still interesting to read about. If there were 4-5 people that I could hit, I'd be in. My location would make a good shot across the bay to link the two shores.

    https://www.arednmesh.org

    Frankly, I'm not sure its really necessary to use the amateur version of these mesh nodes. Why not just set up a MDshooters mesh network?

    Back in the day, it was packet radio. It was a really good system that could have been a lot better but it fell out of favor with the internet. We really need a TCP/IP based packet radio system with backbones that are running on microwave links.
     

    cantstop

    Pentultimate Member
    MDS Supporter
    Aug 10, 2012
    8,158
    MD
    Even when Iraq invaded Kuwait, they kept the communication system up.

    Short of setting up a mobile ham radio system, I just don't understand what is trying to be accomplished here.
     

    Antarctica

    YEEEEEHAWWW!!!!
    MDS Supporter
    Sep 29, 2012
    1,728
    Southern Anne Arundel
    If the shit hits the fan,why bother worrying about what the FCC is concerned with? Smoke signals work well..lmao

    Because you need to get it up and running and tested now, and you don't want to get the FCC on your ass before you're even started.


    **************
    If that weren't the case, setting up your own cell tower with OPENBTS or one of the forks would be cool
     

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