Texting With Some Walkie-talkies

[Travers Buda] is giving new life to his abandoned childhood toys. He cracked open a set of Family Radio Services radios he had received for a birthday which work up to 2 kilometers apart. With just a bit of extra circuitry he was able to get them to act as wireless modems. The system functions but it looks like it would benefit from some more refinement, including error correction. In the end [Travers] manages to send and receive ASCII based messages at a whopping baud rate of 10.

44 thoughts on “Texting With Some Walkie-talkies

  1. Technically, the license granted by the FCC specifically disallows transmitting “data” on the family radio bands, which includes touch tones. But the odds of getting ‘caught’ are pretty much zero… I looked into using these for communication from weather balloons.

  2. I doubt anyone technically cares if it is legal or not… All I hear on hackaday is:
    1. Not a hack.
    2. Arduino.
    3. That’s not safe/ wear eye protection/ wear a helmet
    4. That’s not entirely legal.

    Where’s the true hacker spirit?

  3. @Pilotgeek

    Well, while the same old whines get tiring, but I didn’t know this was technically illegal and appreciate the warning.

    When dealing with feds, ‘Safe keeps you alive. Legal keeps you employed.’

  4. Really? ” Where’s the true hacker spirit? “? Honestly guys. How many of you have thought of this? He took something and though somewhat illigal made use of it in a different way it wasnt intended for. he improved upon it. He hacked it to do something. Just cause its not extreme doesnt mean its not hacking. I say well done.

  5. Had this on my project research list…of course I wouldn’t have researched the legitimacy and legalities as much as how to modify the device. But it is true ignorance is no excuse, so I apprecitate the heads up. Similarly you can’t fly a kit over some altitude without special FAA or similar clearance.

    1. @ vtols, Can someone help me understand why people who are generally intelligent and obviously interested in electronics don’t just do the logical thing and follow in the foot steps of the original hackers – Amateur Radio Operators. The license is cheap ($15 bucks) the test is easy (the questions and answers are available free all over the net. Just Google, “How to become a ham”) and you have access to tons of radio spectrum with which to legally hack your heart out. The laws aren’t there to keep you from having fun. Why not have fun and get a first class electronics education at the same time?

  6. This is very cool. I like that he figured out how to interface directly to the radio and have the MCU do the encoding and decoding.

    This could also be done in software with a package like fldigi and the NBEMS suite http://www.w1hkj.com/NBEMS/ without modifying the radios or creating any kind of interface. You can hold a radio right beside your mic to receive with fldigi and beside the speaker and press the push to talk button to send. Some of the modes supported include error correction and can be much faster.

  7. Sorry, some how I knew my comment would be misinterpreted… I should have stated right off, yes, cool project, even better writeup! I’m sure I’m not the only one who learned something from the write up. I was considering this for, well, not a commercial application, but a wide spread application where I thought paying attention to the rules would be a “good idea”. I would not hesitate to do this for a personal project, as there is pretty much zero chance anyone else would ever notice, more or less know the rules and report me. Oh, yea, and take the time to track me down :-)

    So I didn’t mean to be negative, just wanted to point out some trivia for next time someone needs cheap, low power, disposable wireless communications.

  8. Re-invent the wheel much?

    Hams have been doing this since 1978 at speeds from 300 to 19.2K baud, it’s called Packet Radio.

    Look up ‘packet modem’ and you’ll find dozens of models out there as well as schematics to build your own from scratch. You can also do it entirely in software using a sound card. (Google ‘AGWPE’)

    I’ve seen old modified Western Electric Dataphone 1800 modems connected to radios as well as homebuilt modems using Exar 2206/2211 chips, TI TCM3105 chips and Maxcom MX614s.

    There’s also several designs out there using Microchip PIC devices. Oh right, I forgot, this is Hackaday. If it’s not an Arduino, it doesn’t exist.

  9. Defiintely neat, might be an excuse to check into FRS – Never really been a fan of it due to the legal restrictions on it though; 500mW max and no modifications allowed.

    However, that said, getting an amateur radio license is easier than ever since they dropped the morse code requirement. Got my tech and general licenses a couple months ago, only took a couple hours of brushing up on theory and laws, followed by a $15 fee and a couple of simple multiple-choice tests.

    Why did I mention that? FRS operates at around 467mHz, the closest legal band is 70cm, or 420-450mHz. Not sure what type of local oscillator these radios use (never had one to play with), but it should be possible to replace or modify the LO circuit, drop it into that band, and mess around legally (provided you’re licensed, you only need tech but general is easy enough to get)…Up the power to 5 watts or so (also relatively easy), and now you’ve got a usable system for RTTY based on ubiquitous, off-the-shelf hardware (except for the MCU, but they’re cheap enough)…

  10. “Important Note: We are pleased to announce that the FCC has granted Garmin a waiver that allows the Rino products to send position data on GMRS channels. In addition, Industry Canada has established a license-free GMRS service. Canadian Rinos now allow users to access and transmit their position on Canadian GMRS channels. All you need to do to enjoy these new features is download the latest Rino 110 software.”

  11. Wow. he’s a noob. Addd simple modem chips and get at leas 1200Bps without effort. if you really modify FRS radios you can get 9600bps easily.

    We did this as a learning to hack at the detriot Hackerspace 2 years ago. It was pretty much effortless.

    WE were able to do 1200bps with no hardware mods at all simply using the VOX functions and the soundcards in laptops as the modems. 9600bps was done in the advanced class.

  12. “May I use my FRS radio to transmit data communications?

    Effective April 2, 2003, the FCC changed the FRS rules to permit data transmissions pertaining to location information of the FRS station. The new rules also permit the transmission of brief text messages. The maximum transmission time must not exceed 1 second, and the minimum time before the next data transmission must be not less than 30 seconds.

    Only those FRS radios that the FCC has specifically certified for such data operation may actually transmit data. FRS rules continue to prohibit the attachment of any device to an FRS radio for which use that radio has not been certified by the FCC. ”

    Data IS allowed in FRS, but only for FCC approved devices, like the Garmin. It restricts your ability to ‘add’ data services to an existing FRS transmitter though.

  13. Great hack! I’ve always wanted to do this. :)
    I would love to hear how it sounds.

    Don’t worry about the FCC.
    I’m sure you won’t get in trouble as long as you don’t interfere with the important parts of the spectrum.

  14. I’ve done this in the past using common AM7910 or AM7911 modem chips; there are more modern ones today of course, but they can be purchased cheaply at ham radio flea markets and the required circuitry is really simple.
    Seriously, who cares if it’s illegal if it’s not clearly wrong. If you do everything you can to avoid jamming others transmissions going against the law is the way to achieve lighter regulations and progress. Think about CB and FM radio: they were were both illegal until people using them pushed for a less strict regulation.

  15. Dude, this is kickass. I love seeing stuff where some really mofuckin’ hacking was involved. Screw the regs, I’d love to see the FCC prosecute “some college kid trying to learn about radio”.

    Very very well done, lots of people have had this idea, you made it happen.


  16. @fartface

    Yeah, what a total fucking noob. If he was really smart he would have just used a laptop with a wifi card, or an arduino with an xbee module.

    I *real* hacker would have just used a 3G modem.

  17. Hmmmmmm….. Wonder if we could make this external enough where you could just jack in without needing to mod the radio. Put them in VOX mode and pass messages back and forth. Maybe status messages on a monitoring station.

  18. If he is going to hook it up to a computer anyways, why not just use the soundcard, VOX on the radio and already existing software like Ham Radio Deluxe? Then the radio needs no modification. I used to do this to transmit all sorts of digital modes. I even had a laptop /w webcam that I would transmit with while mobile and the radio at home would decode and save the images.

  19. This is awesome.

    @vtols 2.4 ghz is legal for data in the US (think bluetooth, wifi — though not limited to those two products). The 900 mhz range is also kind of a free-for-all in the US, but I don’t know if you can modulate data over it or not legally.

    @Jaspel the same way your phones, wireless xbox controllers, and any other FCC approved devices do it: They use appropriate frequencies for their regions, (or buy them), and get FCC certified before they go to market.

    @Gibson I’ve heard stories about the FCC knocking on friend’s doors, it DOES happen, they do NOT fuck around.

  20. I’ve also used FRS radios for a reliable medium range DTMF control system on a wheeled ROV back in the late 90’s and early 2Ks.
    (It’s still there actually, in “mothballs”.)

    Generally FRS radios are designed to deter easy modification, but medium to hard modifications are still possible depending on how far you have the knowledge to go.

    Radio is good clean fun.m :)

  21. @vtols
    You could use 2.4 GHZ “bluetooth, wifi, ZigBee” or 900 Mhz “ZigBee”
    To get long range you could build a dish and tracking system with wifi. Use some servers to point and old DishTV Dish modified to use wifi. A USB wife dongle mounted at the receiver horn will work well.
    Use GPS on the ground station and the balloon and then use some trig to keep the dish pointed at the balloon should work. I do not know if the gain would be too high and could be more then the FCC allows. If so get a HAM license and you should be good to go.
    As I said this is a neat hack. Steve Ciarcia modified a Big Trak to get commands sent via a 300 baud modem through some kids walkie talkies back in the yearly 80s or late 70s. Of course he built his own 300 baud modem to do it. Since this was on CB it was also very illegal to do at the time but it got published in a national magazine.
    This is still a cool hack and I feel very impressive.

  22. Why not just use CW code? Or PSK held near the speaker of the digitizing device (PC)? At least with PSK you would get about 30 baud, and can handle a real keyboard to keyboard. I’m fairly sure that the FCC intent with data restrictions on only approved devices, is if the device is actually physically connected.

    That would allow for beyond intended modulation and spurious harmonics. This would be bad. Holding up a mic to a speaker that happens to be blazing psk31 is not illegal.

  23. I just want to say, it’s impressive that this guy is actually smart enough to wire up an MCU on a proto board. I hear lots of n00bs crying for arduino, that makes no sense. An arduino is good help for someone who doesn’t really understand how to construct the hardware, but this guy is clearly better than that.

    Now, 10 baud? Blah. Lol. But hey, at least he tried.

  24. >I looked into using these for communication from
    >weather balloons.

    Several years ago I used FRS radios for a Balloon Project, using plain old fashioned Morse Code to send data. A pair of radios that wouldn’t quite do a mile on the ground in a residential neighborhood, did approximately 23 miles with one on a balloon.

    My original site is down, but I found someone who is mirroring it with-out my permission – http://NastyPrisms.com/temp/cache/www.geocities.com/Almost_There_Weather_Balloon/Almost_There.html

  25. This is a great hack. I’ve done similar with FRS packet radio software and acoustic coupling (as you had suggested). Cheap fm transmitters, cheap fm radios, packet radio software, and a soundcard are a way to do this without physical hacking and I believe there are no restrictions on sending data as far as I can tell. PSK31 can go quite a ways on low power.

  26. I did the same thing a while back, except I just used the hands free port on the radio for the audio interface, and I used an XR2211 to demodulate the received audio. I was using it to transmit DGPS corrections at 300 baud to my GPS so that I could get 1M accuracy in my back yard.

  27. Back in the days of CB radio and spectrum computer me and my mate setup channel channel 41 on 1-40 channel CB radio that was easy then we transmitted spectrum games over radio slow but fun ????

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