TEXT walkietalkies

Discussion in 'General Electronics Chat' started by mattmers, Aug 9, 2013.

  1. mattmers

    Thread Starter New Member

    Oct 17, 2012
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    Would it be possible to make walkietalkies that send text chat instead of voice communication.
    I've had the idea floating around in my head for about 2 years
    I guess it would require custom hardware and software
    the software would require a really basic custom os and kernel
    then the hardware would have to have a transmitter, receiver, basic smartphone hardware (i.e. early 2000s specs) I always picture something like a RIM 5810 or Handspring 180 with a long walkietalkie antenna and a more basic os.

    Could this device really be made?

    Would the signals have to be digital, i don't know much about this stuff so any input would be great.

    The message does not have towers to relay to so the message would be send and any devices within range that is similar would receive the message, i figure the device could then cache the message and display it in conversation form per channel.
     
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Why? everyone now has a smartphone with built in "long range" texting already..
     
  3. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    The little Motorola Digital Walkietalkies can be paired so you don't actually broadcast to every one.

    The project can definately be done. You will need a Microcontroller, an RF transmitter and receiver pair, a display and software to control a shift-keying protocol (Frequency shift keying or amplitude shift keying).

    The question is, are you doing it for fun and personal interest, do you plan that some specific person actually uses it, or do you expect this to be a large scale commercial product?

    Next you will need to start thinking about...
    what range are you hoping for?
    How big will this be, how many characters per row and how many rows of text?
    How long will batteries need to last?
    Will you build a stand-alone from scratch or will you hack off of an existing Walkietalkie?

    More design specs will be needed but that is a start.
     
  4. wayneh

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    Sep 9, 2010
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    Your cell tower coverage must be better than mine. ;) Of course you're right, until you're out of cell range.
     
  5. mcgyvr

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    Oct 15, 2009
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    Can you hear me now?
     
  6. mattmers

    Thread Starter New Member

    Oct 17, 2012
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    I just think it would be a cool personal project if i can get more experienced people involved. It could become a product for younger kids maybe but thats all I can think off. If it is completed i'd like to post how to build it and put all code on github. The range should be about a mile or so and character limits should be choose according to screen size and resolution. Battery should last maybe 4 hours and id like to do it from scratch but hacking off other stuff is fine.

    It would be cool to give each device and id and allow for them to connect to one specifically.
     
  7. wayneh

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    Sep 9, 2010
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    I agree with gopher that hacking an existing talkie solves a huge set of problems and allows you to focus on the text entry and display issues.

    One possible advantage of this project, compared to just talking on the walkie directly, is that I think you could convey a message more accurately over a longer range with a given pair of radios by using a computer to perform error checking and correction. Each message could be sent by the transmitter repeatedly until the receiver responds with "message received". Clever processing could accomplish this automatically. Sort of how the internet works, packets.

    This would be a great way to send a distress signal, using it in un-paired mode.
     
  8. tracecom

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    Apr 16, 2010
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    You could use a switch to send beeps to represent letters of the alphabet, and instead of a screen, the users could just memorize the beep pattern for each letter, and...no, wait...that may have been done. :D
     
  9. strantor

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    Oct 3, 2010
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    I've had a similar fantasy project in mind, but in my version, instead of "like a walkie talkie" it's "like a HAM radio." I would like to be able to send encrypted data to friends in other states, independent of existing infrastructure.
     
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  10. mattmers

    Thread Starter New Member

    Oct 17, 2012
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    I'd be more then willing to merge projects especially if we can get people with more experience involved. I do like the encrypted part, would be great, then it could actually because a product. We could have ham radio models and hand held models all on the same frequencies so they could would together but the ham radio could just have added features and range.
     
  11. KJ6EAD

    Senior Member

    Apr 30, 2011
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    Take a look at existing ham radio packet technologies; there are many. Most transmit data as bursts of audio frequency tones. You could adapt one of these to a microcontroller and GMRS radio. It wouldn't be legal for FRS radios, but GMRS radios are almost as cheap and have a few more channels and potentially greater range.
     
    Last edited: Aug 11, 2013
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  12. strantor

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    Unfortunately for me, this fantasy has been on the back burner for a couple of years and will probably remain there for a couple more. It will take a lot of learning on my part. I know almost nothing about radio transmission. I thought it would be good to get started into HAM radio and figure out the nuances of that before I start reinventing it. But I just don't have the time. But if you have more free time than I, and you go forward with it, I would like to stay in the loop on your progress.
     
  13. THE_RB

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    Doesn't HAM licensing exclude the use of encryption?
     
  14. wayneh

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    Sep 9, 2010
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    I think any form of communication that the NSA cannot - in principle - snoop on will get you in trouble. ;) But there might be a market for it.
     
  15. strantor

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    I don't know. probably...
    ...But if any of the situations in which I envision needing it arised, I wouldn't really care about the NSA/FCC, or they wouldn't be around anymore.
     
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