Get in touch

If you have any general questions or comments you feel might benefit other people as well, I encourage you to post a comment on a relevant page, or use the forum! You can also send me an email by using the address mark at unsigned dot io.

297 thoughts on “Contact Me

  1. Hello I’m IN3AQK,
    I’ve just placed an order for a MicroModem DIY Kit, but ufortunately I’ll probably misunderstand something.
    Could I use it connected to a normal Arduino Uno or Arduino Micro.
    Or the forms factor is for other arduino boards?

    1. Hi Paolo!
      You can use it just fine with a normal Arduino UNO. In fact, it will work with any Arduino compatible board that has the ATmega328p microcontroller ๐Ÿ™‚ A small guide with an example of how to connect the kit to an Arduino is included in the kit, it’s very easy. You just connect a few wires from the MicroModem board to the Arduino pins, and everythings ready!

  2. Perfect, thanks for the info.
    The form factor for which type of arduino is? In the site I’ve seen a photo of the board stacked on an square arduino board. Where I can eventually buy it?

  3. Another question, which version of microduino is more suitable for the Micromodem, 5Volt one or 3,3Volt

    1. Definitely go for the 5V version, as it is running at 16MHz. The 3.3v one is only 8MHz. All the code I have published expects a 16MHz operating frequency, so you would have to change that yourself if you go for 8 ๐Ÿ™‚

  4. Hello
    Assembled modem kit
    but question how to do load firmware APRS modem to Microduino core with USB module

      1. Hey! Sorry about that, but I am having some very busy days at work, just came home from a 13 hour work day ๐Ÿ˜‰ Glad you got it working!

  5. i build it myself, but i think i miss some points, in the schematic, i dont understand witch lines cross and witch not, only in one cross is a point, that tells me to connect…

    1. the line in and mic out part works, but i good ptt always pushed on my baofeng, same as you used, but my cable is fine, use it on a tnc2s as well.
      but the thing is, i checked the mosfet circul and it seems fine, wenn i not send i have no bridge between – and ptt, when i send i have one, but on the ptt wire is a negativ -0.5v it shud be 3v + right?

      1. got it to work, it turns out that i connect the 2n7000 wrong. but it seems to receive not all on the air, my tnc2s get more packets, maybe is it possible to put a poti in it?

  6. I see Microduino-OLED on stock
    can we use it ?? will be fine with micromodem

    1. Should be good, but I’m not making any guarantees ๐Ÿ˜‰ Take a look at the forum post by Taner though, I’m pretty sure that was the OLED he used for his build!

  7. Urgent Opportunity
    Could you please make contact asap in order to discuss the potential for large scale procurement of this product?
    Kind Regards!

    1. Hi Bent! It’s just the standard 3.5โ‚ฌ, or about 26 kroner. Or you can select “Local Pickup” and pick it up yourself, if you’re close to Ringsted ๐Ÿ™‚

  8. Hey there, what a great project you have managed to accomplish!!
    I’ve been looking forward to implement this amazing modem myself with the help of your tutorial and the repository in GitHub, not sure of what am i doing wrong but i don’t seem to even compile the proyect.
    Is there any way i can do it with the Atmel Studio (Visual micro) plugin? (same as arduino IDE i guess).
    I would really apreaciate any help i can get!

    1. Hi Andrรฉs! I’m guessing from your forum posts that you got the compilation working. If not, hit me up in the forum and I’ll help you get the build environment set up ๐Ÿ™‚

  9. MicroAPRS config Serial port, however, Serial 38400 bps, 115200 bps or .HEX compiler program.

      1. Hi Niphon!
        I’m not quite sure what you mean? Are you having troubles flashing a compiled firmware to the modem, or do you want to change the serial baud rate of the firmware?

          1. Ah, just have a look in the “device.h” file. Then change the line:
            #define BAUD 9600
            #define BAUD 115200
            And compile the firmware! That’s all you need to do to change the baud!

  10. Hello,
    we are a B2B Trader in Austria.
    For a big austrian industry company we need one of your products as followed:
    3 pieces MicroModem r23g with Pin Connectors
    Can we buy it directly from you? And can you send us a proforma invoice sio we can pay it immediatly!
    How long will be the shipping time?
    Kind Regards

  11. Can this interface with a GPS such as the Ultimate GPS?
    Can you provide example code and schematics for configuring with a GPS.
    Thank You

    1. Hi Den!
      As far as i know, the Ultimate GPS board just outputs the GPS data over a standard serial port, so that should be no problem. I don’t have one myself, so can’t provide exact code for it, but it should be pretty straight forward: Just poll the serial port for incoming data and parse the lat/lon values from it. Then set them using the commands in the library and transmit a position update!

  12. I would like to use via tcp ip
    with one Arduino .
    Work? .
    receive rx aprs stations
    only the display 16×2
    what value ? Do you send to Brazil

    1. Hi Wladimir!
      I can send to Brazil no problem! I’m not quite sure what you mean by wanting to use TCP/IP though? Do you want to receive APRS data from the internet and the send it over a serial connection to display the data on an LCD display? If so you actually don’t really need the modem, since there would be no need for demodulating a signal. You would already have the data directly available. If I misunderstand you, please elaborate ๐Ÿ™‚

  13. Hi, starting to see a few projects being done based around your modem, and I want to try a few for myself
    Any time frame when the DIY kits will be in stock? or a parts list for just the empty PCB?
    any idea what shipping to the U.S. would be?

  14. Hello, I need to get in contact to you to buy some micromodems.
    Here in Costa Rica, we will launch a LEO satellite. Data came ashore using a link APRS radio.
    I need to install micro modems in some hills in the country, in order to recover the satellite. This activity will be done in August, the event is call Campus Party, it’s a Technology Trade Show for hobbyist and makers. The webpage of the event is:
    We have a few weeks to setup the APRS network and the satellite.
    Best regards.

  15. Hello,
    I am experimenting with APRS and arduino.
    Is there a code or hex file available to flash my arduino (uno) and recieve aprs packages.
    Frist i want to recieve aprs packages and put them on a maps (like
    Later on I want to send gps coordinates back to the first modem; do you have experience with gps coordinations?

  16. Does anyone in the United States sell these? If not, what is shipping to United States Zip Code 83869-0625?

    1. Hi Shawn!
      There’s currently no resellers in the US, but I have them back in stock now. Shipping to the US is only 3.5โ‚ฌ without tracking. If you want it as a registered package with tracking, it’s a bit more expensive at 37โ‚ฌ.

      1. Hi,
        i will order MicroModem, tell me is coming with something like box or wires and how much will cost shipping to Macedonia.

        1. Shipping is 3.5โ‚ฌ for unregistered airmail. Currently not any case or wires included, but I do have a prototype case I can send with it if you order one ๐Ÿ™‚

          1. Did you have also MicroModem DIY Kit ? because i want to order also that ? i just ordered Microduino, so i was mean to order and other DYI Kit from you ๐Ÿ™‚

          2. Your package is on it’s way ๐Ÿ™‚ And with a little extra surprise ๐Ÿ™‚ I don’t have any more of the DIY kits left. Maybe I will order more PCBs for them at some point, but I don’t know when.

          3. Thanks Petersen i will make then because in github there is everything

          4. I just got it…. well man… this is perfect… also case for modem is awesome ๐Ÿ™‚ thanks a lot.

  17. When will the Micromodem be back in stock? I would like to purchase a couple more.

  18. Hi Mark, i will need one MicroModem DIY Kit , do you have still that ? i want to order one with case for that and audio pins ๐Ÿ™‚

    1. Hi Bosko!
      Unfortunately I don’t have any more of the PCBs left. I might have a new batch made if there is enough interest from people for the kits.

  19. Do you know when you will have the micromodem back in stock? I would like to order one.

    1. I have new orders in at the PCB fab, and also for components, but probably wont have stock until late december. I usually make 50 piece batches, but I’m upping the next one to a couple hundred probably since they sell out quite quickly ๐Ÿ™‚
      Still not decided on doing another run of DIY kits, but will post if I do ๐Ÿ™‚

  20. I would like to order one micromodem. When will you have them in stock again?

    1. The modems will be back in stock soon, please check out the latest post on the blog ๐Ÿ™‚

  21. Currently doing research on building a cubesat and since we’re using only commercial off the shelf parts this modem seems like a great way to get our telemetry data back to the ground station. Being completely new to this I had a question. Would it be feasible to cut out the modem usb –> computer connection and have the actual arduino supply the data that we would like transmitted (if we had sensors recording data also connected to the Arduino) or would that be too much to handle for something like the Arduino Uno? If that isn’t possible I was thinking I could connect the modem via USB to another microcontroller (if possible) but we’re trying to minimize power consumption by doing it all on one board.

    1. You can easily bypass the USB connection! If you buy the modems from here you can use the UART port directly on the modem for a direct serial connection to another arduino for example. If you build it yourself, just be sure to add some connectors for the serial pins!

  22. Hi Mark,
    congrats, good work! I like to order one modem. Is there a chance to get one?
    73 de Mark

  23. Hi Mark,
    first of all again congrat to your excellent work! It’s a lot of fun building things around… I just have a question, after running a coulpe hours the MicroModem the Path change by itself for example ti “WIDE1-1,9-2”. Any ideas?
    73 Mark

  24. Hello !
    I have a question how to draw more shapes and letters.
    Please help !
    Best “ARDULASER” project !!

  25. Hi Mark,
    I need your help. Last year I bought a Micromodem rev1 A1 board from you.
    I lost the manual that show me what pins to connect to the arduino nano. please
    let me know if there is a pdf file for this. thanks for your time.
    73’s de NP4ZB/JORGE

  26. Hello,
    Can you please recommend a micro transceiver dev board that work with 144.390 or could use per programmed 2-Meter freq.
    KM4QDC, Jim

  27. hello ‘I write to you from Argentina and I want to arm the ardulaser, but can not find the wiring diagram or diode board or full codes, could help more specifically?

    1. Unfortunately I don’t have that anymore ๐Ÿ™ It was build a loooong time ago, and I lost the files somewhere along the way.

  28. Hi Mark,
    I tried to register with my callname IU3GMS, but something went wrong at mail server, so I can’t register again. please check the user db.
    I am using your LibAPRS on a Genuino Mega and a SimpleSerial on a Nano, that are “talking” together succesfully (for the Mega I have changed the port definitions).
    I made a little change on AFSK.h that has determined a very high percentage of success in decoding.
    It seem strange, but this change consists on the inversion of mark and space frequencies.
    As this articles says (, I saw a very high quality on 1200Hz note and a poor quality in 2200Hz.
    the transmission started with 2200 tone, the receiver heard that frequency and than the frequency transitions.
    Starting with 1200, the receiver decode and sincronize better.
    Have you ever tried this?
    Sorry for my english.
    Best regards,

    1. Hi Luca
      That’s very interesting, thanks for sharing. I’m going to try that myself, and if I can reproduce the same improved performance, I’m going to implement that change. Thanks for the tip!

  29. Hello, will there be some modems in stock soon?
    Would love to get one.
    mny73 DG0JUW

      1. Hi there.
        Just wondering if or when there will be another restock of the shop. I would love to get one from you.
        73 DO2CHF

        1. Hi! There will be stock again in November. I’ll make an even bigger batch this time, they always sell out way faster than I anticipate.

  30. I am looking for 10 to 20 Bell 202 Dumb Modems for a special application in the alphanumeric paging service. The modem I have been using for the last 20 years is no longer in production.
    My requirements are as follows: Dumb Modem (I have my own control signals). 300 to 1200 baud.
    Standard Bell 202 tones.
    In my application I use Audio in (FSK) Data out (Capable of Normal or Inverted polarity.
    +12 Volts and Ground. 300 Baud Rate. And that is it.
    Can You help me.
    Thank You

  31. Hey Mark,
    please drop me a line when you are on stock again. Just wan’t to place an order of one or two modems and cases.
    73, Silvio

    1. Hi Silvio! Sorry for the slow response! There will be stock again in November. I’ll make an even bigger batch of everything this time, promised ๐Ÿ™‚

  32. I am using Code Blocks on a windows 8 computer, how do I get the micromodem source to compile? it can’t seem to find all the micromodem includes.

    1. I’m sorry, but I don’t use Windows, and don’t know about Code Blocks. If you have avr-libc installed, that will be all the includes you need. Maybe you need to set up a path to the libraries in Code Blocks?

  33. Hello, I can’t register on the forum, so I ask here.
    I just built the PTT and “soundcard” parts separately (first sending, second receiving data). I modified arduino APRS firmware (I left only raw data send and receive functions, I don’t need APRS at all, just AFSK code and a little AX25 code) and started testing!
    sending part is Wouxun UVD1P, arduino nano 168 5v;
    receiving part is Baofeng UV-5R, arduino pro mini 328 5v;
    They are both on the table, 20cm between.
    Everything work good, I’ve sent millis() and received in terminal. OK. but… may be 1 of 20 packets is lost.
    I know it’s only ~5% of loss, but is it okay? (only 20cm between radios). I don’t have oscilloscope and my radioschematic knowledge is not perfect (as AVR programming, too), but if someone will direct me, will be good!
    P.S. APRS arduino lib don’t have CSMA and error-correction, I will try to implement them. My goal is to implement simple mesh network with GPS location updates and encryption by key.
    Please excuse me for my dirty english. Thanks!

    1. Hi Roma!
      I think 5% packet loss sound a bit high. Actually try moving the radios a little further apart, and if you are transmitting at higher power, make sure there is also at least 50cm between your modems and radios! If that does not change anything, I would increase the TX preamble a little and also make sure the input and output levels are well adjusted. This can be hard without an oscilloscope, but with a little trial and error, it should be possible to get it dialed in almost perfectly ๐Ÿ™‚

      1. Thank you, now it works perfect! My fault – wrong some of resistors rating.

  34. Primero darle la enhorabuena por su proyecto y el exito que esta consiguiendo, solo queria saber si el MICROAPRS es un emisor de aprs, ya que lo que busco es un circuito que obtenga datos gps y conectarlo a un walkie y que este transmita la informaciรณn a un receptor que ya tengo instalado. Gracias por su atencion y su buen trabajo

  35. Hi Mark,
    just wondering whether a new batch of micro modems will be available soon? (You mentioned November further up?)
    tnx and best 73,
    Peter, HB9TVK

  36. I am looking to purchase several Micromodems in the near term. Do you know when they will be back in stock and can be shipped to the US?

  37. Hello Mark,
    I am not able to reply to threads due to still missing confirmation from administrator.
    Could you please acknowledge my request in the forum intruduction or delegate it to somebody?
    Pete, Germany

  38. I just finished building your micromoden, but I can’t set the “PATH2-1 SSID to 1
    I sent the modem “s21” this will not change the path, how do I change the path ssid?

  39. Hello Sir.
    micromodem is out of stock.
    do you expect restock?

  40. Do you have more modems ? if you have that i will buy one for testing and if i can use it i will buy about 16 pieces of that !!!
    best regards
    Heino Jorgensen
    de sm7mdo

    1. Hello Heino!
      I am all out of stock right now, but will have more in 2-3 weeks. Demand has been much higher than my production capacity for a while now, so I have been upgrading my workshop to be able to produce more units faster. I will start production of the new batches in 10 to 14 days, so if you can wait for it, they will be available again soon!

  41. Hi!
    I use your software midi katapult a lot for videosampling in Ableton Live. I would like to know if it is possible to make the launchpad mini (or the newer launchpads) compatible because the only one that work is the original launchpad. Is there a firmware sdk form novation that I could use? Thanks

  42. Hi Markqvist,
    I would like to order a pair of Micro Modems for an experiment. When will they be available? Also, can t he code be modified so it can be masked from the audio stream going to the transceiver? I intend to do that by using a very high cutoff HP filter, passing only frequencies above 400 HZ to the speaker amplifier. I don’t need high baud rate. I imagine the code is flexible enough to tailor the FSK frequencies.
    Jerry Peck

  43. Hi Mark, I was wondering: If you increase the number of DAC bits to 6 or 8 the signal out wuld be much better ?

  44. Dear Mark,
    I have been working on making a micromodem. In the documentation, you write, “The git repo includes a prebuilt .hex firmware file you can upload to the modem.” Are these the four .hex files located in the “precompiled” directory?
    Thanks for a very detailed and complete project. I am afraid my skills are not up to the level of writing my own changes to the software, BUT, I have really enjoyed pushing past my ignorance and learning WinAVR, avrdude, and learning what a bootloader is. I hope you haven’t abandoned this project yet.

  45. Been looking into building one for the fun of it. So far so good minus a few hiccups. I just have a few questions about the settings for the transmit delay and tail using the kiss protocol version. How can I set these? I noticed some general information saying it could be set in the kiss version, but nothing describing how. My plan is to use it with APRSDroid and Xastir on the computer. Xastir has settings for these but don’t seem to do anything. APRSDRoid does not have these settings.
    Can the code be edited and compiled to accomplish this? Or some other method?

  46. Hello,
    I’m in the USA and been dyin’ to purchase a couple of the MicroModems..
    How do I go about making a purchase?

    1. Hi Marc,
      They were out of stock for a while because I didn’t have time to make enough modems, but there’s more stock now, so you can just order however many you need!

  47. Hi
    Would it be possible witht eh micro modem to open a website?
    i’m looking for something that can connect to phone line and when someone calls open a website
    where XXXXXXXX is the phone number and YYYYYYYY is a password

    1. Hi Bo
      Something like that would be possible, but since MicroModem is primarily designed for radios, you would need to add a little extra circuitry to “pick up” the phone when someone rings. You’re welcome to send me an email with a bit more info on what you want to do, and I’ll try to guide you in the right direction!

  48. Hello Mark,
    What are the shipping costs for Europe / Italy, and what timing are there from the order?
    Thank you

    1. Hi Mimmo
      There’s several shipping options to Italy. I’ll list them here below:
      Untracked postal package: 5.5โ‚ฌ, approximately 6 days.
      Tracked and registered package: 18โ‚ฌ, approximately 4 days.
      GLS Europe: 29โ‚ฌ, approximately 3 days.
      I usually ship out orders on the same day I receive them, if I get the order before 14:00.
      Let me know if there’s anything else you want to know!

  49. Hi Mark,
    I teach along the coast of Maine (USA) and would like to engage them in an electronics project. We have been playing with Arduinos and a couple have expressed interest in doing something like a High Altitude Balloon project, which I’ve done before with APRS beacons. Being on the coast, I’d like to try making a sounding buoy as well. These project ideas have something in common that hasn’t really been done much – an on-board “flight computer” which can transmit telemetry but can also receive commands. To do this, I’d like to use something like your MicroAPRS board – which I saw on your YouTube channel. It looks like something my students can “build from scratch”, which is important because I want them to feel like it’s their own project, and therefore something worthy of their time and attention. From your experience, would your MicroAPRS board work well? I have a radio for the remote unit and am starting to consider how the ground station should work, as I plan to use Processing to design a GUI for the ground station, to give it that “mission control” feel.
    — Markus

    1. Hi Markus
      Sounds like a great project. I actually used to sell kits with PCB and through-hole components for building MicroModems, but I don’t carry those in the shop anymore. It’s still quite easy to assemble a working MicroModem on a breadboard or prototype board though, so it should be no problems. If you haven’t already found the schematics and such, they are all available on my Github page.
      I think MicroModem would be a fine fit for the project. You could use the default firmware, or create a custom one using LibAPRS, depends on how you like to implement it really.
      Sounds like a great idea with the Processing GUI! If it all comes together, please send me a few photos, would love to see how it turns out!
      Kind regards, Mark

      1. Outstanding! I have a question for you, since my tech knowledge is self-taught… I ask my friends about this and they say “oh yeah, a serial connection” like that explains the whole thing. And I’m sure it does – for them at least! So I’d like to ask what’s happening “under the covers” – feel free to direct me to resources you know of, they may have more information than what I’ve been able to find.
        I see that, at least in the YouTube video, your MicroModem forms the “bridge” between the Arduino and the radio. While I can understand the serial data between the MicroModem and the Arduino, I’m still trying to wrap my head around the signals moving between the MicroModem and the radio. How is the MicroModem generating the sounds – the chirps that sound like a fax machine – that are transmitted to the radio?
        — Markus

        1. Hi Markus
          Sorry, I had been very busy, and forgot to get back to your comment. The modem is internally synthesising the sounds in software. A loop is running 9600 times per second, and calculates the analog voltage level to output based on what audio frequency the modem should output. Then, this analog voltage is achieved in the real world by using a 4-bit DAC connected to four of the logic pins.

    2. UPDATE:
      I think the approach I’m going to take is to use two Arduino units. One will be the MicroModem to handle communications, the other will be the actual flight computer to receive commands and send telemetry. If I can make this work with off-the-shelf parts, I’ll probably look to make a specialized PCB design that incorporates both Arduino units. We’ll see!
      — Markus

      1. Yeah, it’ll probably easiest to start out with two separate Arduinos. That way you can just use the precompiled firmware on the modem Arduino, and have all your control code on the other one.

        1. So… I just realized something from your comments. My goal is to give students a hands-on experience with technology. This is why your hardware approach is the perfect match for what I’m trying to do – it’s an Arduino (which a student could make from scratch if they wanted to) and the MicroModem that a student can solder for themselves. I’d really like that kind of experience for the software side as well. But I see in your comments that the MicroModem coding for the Microduino is a “black box” experience (precompiled firmware.) I know I’m asking a lot, but is there any way I could talk you into sharing your original Arduino IDE sketches? Or some “Microduino Light” sketches with basic APRS functionality? I’d like students to work with the actual files and upload them to the Arduino. This would help students see that rather than “waiting for someone to develop an app”, they can get in and make things happen themselves.
          — Markus

          1. Sure, all the source code for the MicroModem firmwares are available on my GitHub page already!
            AX.25 firmware:
            I did not use the Arduino IDE environment for those firmwares though, as it is a bit limiting when you’re used to just using a plain old GCC toolchain.
            But I absolutely understand the appeal of the Arduino IDE, so that’s why I wrote LibAPRS. It’s a library that can be added to the Arduino IDE, that contains all of the heavy-lifting code for modulation/demodulation, line coding, DAC output and so on. That way you can just code actual programs, and not worry about the really complicated stuff. Here’s info on the library:
            I think that will do what you want. The students can use a standard Arduino Uno or similar, and solder all the MicroModem components on a separate board, that can then be connected to the Arduino, and they can write code and upload to the completed modem from the Arduino IDE ๐Ÿ™‚

  50. Hello Mark,
    since i am interested in the code of your micromodem (i own one), but i am not very skilled in
    programming, i have a fundamental question:
    Nearly all Atmega328-based modems (trackers) use one digital out pin for the AFSK.
    I know, that this is done by performing a PWM with a sine table.
    Why are you using 4 pins and how is it done ? Is the Atmega328 working as a kind of 4 Bit DAC ?
    Is it possible to explain to me ? Normally my world is hardware – not software ๐Ÿ™‚
    best regards, 73 de dc1mak micha

    1. Hi Micha!
      Yes, the four pins are used as a 4-bit DAC, you are exactly right. It yields a higher quality signal than just using PWM on one pin. The modem is synthesising the correct frequencies for the AFSK signal in software, and translating to analog values through the 4-bit DAC at 9.6KHz sample rate. Hope that makes it more clear!
      Kind regards,

  51. Hi Mark,
    Another question… I’m building the MicroModem from scratch. Rather than using a MicroDuino, I’m using an Arduino Mega, since it has the extra pins. Can you give me an exact list of what files (APRS.h, AX25.h, etc) will need to be included in my Arduino sketch? What is the syntax for sending and receiving a message coming from my radio?
    — Markus

    1. I have components incoming, and will be restocked on november 14th the latest.

  52. Hi Mark,
    I have all the components and am starting to assemble them on a breadboard. I’m using ../ModemMicroduino/Modem.sch as the schematic. However I’m having some difficulty with the layout. There are places where the traces cross and they have a dot, indicating that the traces are connected – such as where R9 meets D3. However there are many other places where it’s not clear if the traces touch or not – such as R1, R2, R3, and R4 – there are two places where traces cross on their way to C1. Would it be possible to get an updated schematic that has a dot wherever the traces connect?
    — Markus

  53. Hi
    I am SATYA, VE3YSN.
    Can i use Micro modem as TNC to connect my FTM100DR ( Yaesu) , for packet communication, to use winlink, outpost etc.,
    thanks and 73s

    1. Hello Satya!
      Yes, MicroModem works for this purpose! You will just need to make a cable to connect the DATA port of the FTM100DR to the audio port of the modem, and you are good to go.

  54. Hi Mark,
    Sorry to be a pain but I really want to get this up and running! I need some additional information regarding how to connect the MicroModem to the radio. I’m looking at the three connectors for the 2.5mm plug (sleeve, ring, tip) and the three connectors for the 3.5mm plug (sleeve, ring, tip.) I’m also looking at the schematic which has three “Radio” lead, one “PTT+” lead and one “PTT-” lead. Can you tell me what lead should be connected to what connector on each of the plugs?
    — Markus

    1. Hi Markus! No worries!
      The pin options can be a little confusing, since itโ€™s made to support as many different radio types as possible. Iโ€™ll explain it in general terms here, if you let me know what radio you use, I can probably provide more specific info.
      The โ€œAUDIO_INโ€ and โ€œAUDIO_OUTโ€ pins are pretty easy, AUDIO_IN is connected to the speaker/headphone output of your radio. AUDIO_OUT is connected to the microphone input of your radio. If your radio has a dedicated data port, use the in/out pins of that.
      For the PTT part, there is a variety of options. There is one pin just labeled โ€œPTTโ€. This is a 5V logic signal that is turned on when the modem requests PTT. So just before the modem starts transmitting, this pine goes from 0V to 5V, and stays at 5V during the entire transmission. Some radios have a โ€œdirectโ€ PTT input like this (mostly mobile and base station radios, and almost anything with a dedicated modem or data port).
      The other options is using the pin labeled โ€œPTT_V+โ€. This option is mostly for use with handheld radios. Some radios supply a positive voltage on a pin of their headset connector, and when this pin is connected to ground, the radio will open the transmitter. Think of it as a simple push-button on a headset being pressed, and shorting the positive voltage to ground. The radio detects this, and opens the transmitter. As stated above, most handheld radios use this method. You just find what pin your radio supplies this voltage on, and connect it to the โ€œPTT_V+โ€ port of the modem. When the modem requests PTT, it will internally short the PTT_V+ port to ground, and the radio will open up the transmitter.
      As a last resort, you can use the modem by using your radios VOX function, but I really donโ€™t recommend it, since โ€œrealโ€ PTT is much more stable and performs better.
      I hope that helped! If youโ€™re still having trouble, let me know!

      1. Hi Mark,
        Thanks for the info – very helpful to have that background! I’m tinkering with three radios – a Kenwood TH-D7, a Baofeng, and a Yaesu FT-2800m. I’m working off the schematic you have posted at – specifically the pin-outs that seem to be related to the radio connections. I see a “Radio” block, containing pin-outs for “Line_Level_In”, “Mic_Level_Out”, and “Ground”. I see the “PTT+” block containing a pin-out for “PTT_V+”. I see the “PTT-” block containing a pin-out for “Ground”. I need to figure out how these connect to my plugs: 3.5 mm Sleeve, Ring, Tip and 2.5 mm Sleeve, Ring, Tip.
        — Markus

        1. Are you using a self-made modem, or one you bought from me? Since you are reffering to the schematic for the do-it-yourself version, Iโ€™m guessing itโ€™s a self built one?

  55. Yup – building it myself. The hope is to be able to do this with students so they can build the electronics more or less themselves so they can see that not everything is a “black box” and they can actually make things.
    — Markus

    1. Ah yes, that’s right, sorry couldn’t remember!
      That’s right, the schematic you are looking at is the old “DIY” schematic, it is a bit simplified, and only has the pins “PTT+” and “PTT-“, not exactly like I described it in the above. You can add the logic level PTT signal like in the “full” MicroModem, by looking at the PTT schematic here:
      Since you’re going to be using a variety of different radios, I’d really suggest you familiarise yourself with how the PTT function works on the different types, then it’ll be easy to know how to hook things up for any radio. Also, a google image search for something like “[radio name]ย ptt pinout” will yield a lot of help in knowing what pins are what on various radios!

      1. Hi Mark,
        Thanks for the info! since I’m working with the “old DIY schematic”, I’d like to stick with that. (I have all the parts picked and installed on a breadboard at this point.) I’ve also been studying your YouTube video for this. (
        Basically, I feel like I understand the general schematic, but I’m having an “apples to oranges” moment trying to understand what part of your circuit connects to what plug going into the radio. If I focus on the Kenwood unit, I can see the schematic for the speaker and mic plugs. ( – see page 96).
        I just need a list of what part of your circuit connects to what part of the plug (tip, ring, sleeve) for each of the two plugs (mic and speaker).
        — Markus

      2. Hi Mark,
        Thanks for the info! since I’m working with the “old DIY schematic”, I’d like to stick with that. (I have all the parts picked and installed on a breadboard at this point.) I’ve also been studying your YouTube video for this. (
        Basically, I feel like I understand the general schematic, but I’m having an “apples to oranges” moment trying to understand what part of your circuit connects to what plug going into the radio. If I focus on the Kenwood unit, I can see the schematic for the speaker and mic plugs. ( – see page 96).
        I just need a list of what part of your circuit connects to what part of the plug (tip, ring, sleeve) for each of the two plugs (mic and speaker).
        — Markus

        1. Hi Markus
          I can understand that diagram on page 96 can be a little hard to decipher, if you’re not used to it ๐Ÿ˜‰ Here’s a simplified connection diagram I found by googling “kenwood tnc pinout”:
          That should make it absolutely clear what goest where. It’s the same way for 99% of all radios that use the Kenwood style connector. The PTT pin connects to the PTT_V+ pin on your modem.

  56. Hi Mark,
    Going tho. the tread, I want to be clear, before I place the order on Micro Modem
    I use YAESU,FTM100DR, which has 10pin data port..
    May I know , the connections diagram from PC – Modem – Radio..and want to use the Modem for Packet transmission AX.25

  57. Hi Mark – apologies if this is a repeat – the website wasn’t posting my note so I sent it again.
    Thanks for the info! since I’m working with the “old DIY schematic”, I’d like to stick with that. (I have all the parts picked and installed on a breadboard at this point.) I’ve also been studying your YouTube video for this. (
    Basically, I feel like I understand the general schematic, but I’m having an “apples to oranges” moment trying to understand what part of your circuit connects to what plug going into the radio. If I focus on the Kenwood unit, I can see the schematic for the speaker and mic plugs. ( – see page 96).
    I just need a list of what part of your circuit connects to what part of the plug (tip, ring, sleeve) for each of the two plugs (mic and speaker).
    — Markus

    1. Hi Mark,
      Thanks for the info! I’m just a little confused about the diagram you sent me. It has four leads (Mic, PTT, Spkr, Gnd) but your schematic has six leads (PTT V+, Gnd(1), Line Level In, Gnd(2), Line Level Out, Mic Level Out.) Can you tell me what connects to what? It’s a Kenwood radio, so can I assume:
      3.5mm (Sleeve) PTT PTT V+
      3.5mm (Ring) Mic Mic Level Out
      2.5mm (Tip) Spkr Line Level In
      2.5mm (Sleeve) Gnd Gnd(1) and Gnd(2)
      Is that close?
      — Markus

      1. The blogging software took out some characters – let me try it this way:
        3.5mm (Sleeve) PTT <> PTT V+
        3.5mm (Ring) Mic <> Mic Level Out
        2.5mm (Tip) Spkr <>Line Level In
        2.5mm (Sleeve) Gnd <> Gnd(1) and Gnd(2)
        Does this look like the correct way to connect these?
        — Markus

        1. Hi Markus
          Yes, I’d say that looks good! By the way, it should be the same connection for those cheap Baofeng radios, if you use those as well.

  58. when do we get the micro modem case?
    Shall I wait to place an order for Micro modem, until you get the stocks for the case ?

    1. I will have them in stock again in the beginning of January, so if you want the modem quick, you can order that now, and order the case later, or you can wait and order it all together.

  59. Hi Mark,
    I think I have the hardware all set for the MicroModem!
    Now I’m moving on to the software. I see that you have some firmware files available. However because I eventually want to do this with students, I’d like them to use the Arduino IDE, since they’ll be using that for uploading other kinds of sketches to their Arduino. Therefore, can you tell me which files I’ll need and what sketch I need to upload to the Arduino to complete the process?
    — Markus

    1. Hi Markus
      My suggestion would be to start off with one of the premade firmwares, just to test that the hardware is all working. The โ€œSimpleSerialโ€ version of the MicroAPRS firmware is very easy to communicate with over a serial console, it has a text driven interface with an interactive menu and help.
      Once you know the hardware is OK, you can use LibAPRS (look in the โ€œSoftwareโ€ section of my site) to easily program sketches in the Arduino IDE that can send and receive packets. LibAPRS takes care of all the heavy lifting of modulating, demodulating, packetising, checksumming and so on, and presents a simple API to send and receive data. Thereโ€™s some included examples in the library to get you started.
      Kind regards,

      1. Hi Mark,
        This sounds cool! I want to confirm though – the “SimpleSerial” version of the firmware, that’s something I need to flash to the Arduino using an ISP programmer, correct?
        — Markus

        1. Hi Markus
          No, you don’t need an ISP programmer! Just upload it to the board over USB with the avrdude program. I personally find using avrdude easiest, especially on Mac and Linux, but if you’re on Windows and would rather like a GUI, there’s a free program called “XLoader” which you can use as well.

  60. Hey Mark – Success! I still have a long way to go, but tonight I loaded the firmware and when I entered stuff into the serial monitor, it keyed the radio and transmitted! So I’m on the right path. Thank you for your patience – both over the past couple months and the questions still to come. Much appreciated!
    — Markus

  61. Hi from Istanbul, TA2IBT.
    I’m a Search and Rescue member and responsible for communications. We need a communication module for teams comm. We can use PC-micromodem-radio combination for chat as youtube video : (
    We need something like a two way pager. We give pagers to our volunteers. Each pager has ID coded. In emergency situtation, we want to see where they are, are they active or passive for duty (they select) and communicate with all (send message to group). We maybe connect with phone (bluetooth) to send and receive messages.
    – Send active APRS position
    – Receive active APRS positions
    – Send message
    – Receive message
    We need (I think) :
    – Micromodem
    – GPS
    – Screen
    – Bluetooth
    – Battery
    – Case
    – Radio connection cable
    – Keyboard (?)
    APRS Screen Sample :
    Is it possible to with micromodem? If it is possible, can you show way and true combinations. Thanks.
    Burcak TURKAY
    AKUT Search And Rescue Team

    1. Hi Burcak
      Thanks for contacting me! There’s several ways to do what you want, so I sent you an email at the address you specified here, so we can discuss the details!

  62. Hi Mark,
    If I may, a small piece of feedback from someone who doesn’t have an engineering background but is willing to tinker until everything goes right. I absolutely *love* that you have something people can build themselves from scratch. As you move on to new versions of your board, I would ask that you keep the “do it yourself” option up to date or even expand it. It would also be really handy if the schematics continue past what you currently have to include wiring all the way to the plug. (I understand you can’t do this for all radios, but I think if you did it for just one radio, people like me could use that and adapt it to whatever radio we’re using.) Now that I have a functioning breadboard – and all the notes I’ve made about the journey to get to this place – I’m looking forward to tinkering over the course of the winter!
    Thank you again – for your resources, your patience, and your willingness to answer questions!
    — Markus

    1. Hi Markus
      Thanks very much for your comments and suggestions, I appreciate it. I agree that the DIY versions and resources should be kept more up-to-date. It’s something I’ve also wanted to do, but since I don’t really know how many people still use it, I’ve prioritised it further down a very long list of what I want to do. All of is basically a one-man operation, and unlike many others who just have a fab in China do all production, I actually produce all the hardware myself in my small workshop in Denmark. So between design, production, programming software and user support, it’s a constant balancing act of time. That being said, I will definitely try to get some time in to update the DIY instructions here in January or February.
      Kind regards,

      1. Outstanding! And happy to help in any way I can. (I’m a technical writer and educator – would be delighted to take on whatever would make your burden lighter.)
        Happy New Year!
        — Markus

        1. Thanks a lot Markus, I will probably take you up on that! It would be a very great help! I am currently working on the final design of a new modem coming out soon, and after that, I will get in touch with you about this.

          1. This sounds great – can’t wait to see the new modem! If I may… playing around with APRS stuff this week, I’m starting to understand about telemetry and how it’s displayed on It would be super cool if you could include a couple sensor inputs in your new design.
            — Markus

        2. Here’s a little sneak preview of a prototype of the new modem I’m currently doing some testing on:
          You’re not the first to request that, so there is now 4 user IO pins on the modem, that can be used as digital inputs or outputs, or analog inputs. There’s also free UART port that can communicate with whatever you’d like, and expansion ports for GPS and Bluetooth LE modules on board.
          The PTT circuitry has been much improved, and four different PTT styles (should cover 99.9% of radios) are now selectable just by moving a jumper on the board.
          Lot’s of software improvements as well. The modem is now both AX.25 and Ethernet compatible, and supports 300, 1200 and 2400 baud AFSK, selectable in software.
          You’ll also notice there is now an SD card slot, useful for many things ๐Ÿ™‚

          1. Wow – this is a major upgrade in options and capabilities! Awesome!!

  63. Ok Mark – time for the next leap in my learning! I have implemented the serial firmware on the open source MicroModem, as we’ve discussed. Now I want to take the next step of building my own firmware. I’m guessing I need some libraries, but not sure what I need beyond APRSLibrary. I’ll see what I can put together, but suggestions and cautionary tales welcome!
    — Markus

  64. Hi Mark,
    Question about the jumpers you use with your machine pins – I see it’s solid core wire with some kind of black collar around it. Just wondering what you use.
    — Markus

  65. Hi Mark,
    Another question – I’m using your file Basic_usage with the make-it-yourself modem. I ran the pre-compiled firmware and was able to make it work correctly. However the Basic_usage sketch is behaving oddly. I put in the necessary information (my callsign, destination callsign, etc.) and it will transmit a packet. However when it does so, the two LEDs both light dimly. The radio transmits for what seems like a long time. When it’s done transmitting, there is a very brief pause before it tries to transmit again. This doesn’t seem right. Is this something you’ve seen before?
    — Markus

    1. To add some detail – I’ve tried this with both a Baofeng and a Kenwood D-7 and I get the same response. If I run the sketch with no radio attached, one of the LEDs comes on which seems to correspond to a transmission. As soon as I connect the radio, it behaves as noted above. This is set with the ADC at 5v. When I change the ADC setting in Basic_usage to 3.3v, the behavior is different when connected to the radio. The LED I assume is the transmit light comes on fully (no dimming) at the same time the transmit light on the radio comes on. However it doesn’t key the radio. Not sure what’s going on here…
      — Markus

      1. Well OK! So now it’s behaving appropriately, I have no idea why. Something else I’ve noticed – the serial monitor only contains garbage characters. Will tinker with this more and see what happens.
        — Markus

        1. Well there it is! (Funny how posting on a board helps you find the answer sometimes!) I see the line: Serial.begin(115200) – so changed the serial monitor to 115200 and voila! ๐Ÿ™‚
          — Markus

  66. Time for “Name That Function” in the “Basic_usage” file! There is a function called “processPacket()” called at the end of the file. I can’t find this function anywhere, even in Internet searches. Any idea what’s being called?
    — Markus

    1. The processPacket() function is defined in the Basic_usage file. Have a look here:
      As the comments state just above the function definition: “Here’s a function to process incoming packets. Remember to call this function often, so you won’t miss any packets due to one already waiting to be processed”
      As you can see in the code, the processPacket() function formats and prints out the received packet to the serial monitor. You might have noticed that there is also a aprs_msg_callback() function at the top of the file, that gets called when a packet has been decoded. So why not just print out stuff directly from this function? Why does the aprs_msg_callback() function simply copy the packet to another memory location, and set the “gotPacket” flag to true?
      As you can read in the comments just above the function, the aprs_msg_callback() function will get called from within an interrupt. That interrupt needs to run 9600 times a second, so you only have about 0.1 milliseconds to execute code in each interrupt run. Printing out to the serial terminal takes a long time, so we need to execute that from the main program loop. That way the interrupt can, well interrupt, the slower running code, and everything will work. If the serial printing was being executed from within the interrupt code, demodulation and decoding would not be able to work while the packet was being printed out.
      I highly encourage you to read through all the code in the Basic_usage example, and all the comments, a few times, from end to end. It should answer most questions ๐Ÿ™‚
      It would be awesome if we could work together at some point on improving the documentation for all of this, as you suggested. I’m primarily a programmer, not an educator, so while I try to make things as clear as possible in the documentation, it doesn’t always work ๐Ÿ˜‰

      1. Well I feel a little silly now… I did look through the whole file, and even used the search functionality. Not sure what was going on but thanks for the clarification! And yes, I’m up for helping out however it’s handy, particularly during the summer when school is out of session.
        — Markus

  67. A couple more questions about the “Basic_usage” file – neither of them about things that aren’t working:
    1) On line 18, there are comments that start out, “You always need to include this function…” – can you talk a little more about what function this is referring to?
    2) On lines 28 and 29, it talks about printing info, ending in “… from your main loop, like this:” – was there supposed to be something else there? The next line of code talks about setting the value for “gotPacket” but doesn’t deal with printing.
    Apologies if this feels like I’m picking at small details, but I’m still learning how this all goes together and need to make sure I understand things correctly, though I’m sure this is one of those “everyone else gets it” items… ๐Ÿ˜‰
    — Markus

    1. The comments starting on line 18 refers to the aprs_msg_callback() function. The aprs_msg_callback() is not called by the user, therefore you won’t find a reference to it inside the “Basic_usage.ino” file. Rather, the library itself calls back to this function when a packet has been decoded.
      No, there was not supposed to be something else in there ๐Ÿ˜‰ Try reading my previous comment again, and specifically the part starting with “So why not just print out stuff directly from this function?”.
      As mentioned before the aprs_msg_callback() will get called from an interrupt. You can’t do anything that takes more than approximately 0.05 milliseconds inside the aprs_msg_function(). If you’re unsure exactly what I’m talking about when I say “interrupt”, try to read up on that topic. I know it’s a bit daunting when coming purely from the Arduino environment, which abstracts those things away, but you need at least a basic understanding of how an interrupt works, to understand why the code in the example is set up as it is.
      To try and sketch it out, the aprs_msg_callback() function will not print anything out itself. It will just do two very simple things. One, copy the contents of the packet to a variable that the main program has access to, and two, it will set the variable gotPacket to true. That’s all.
      Inside the programs main loop the processPacket() function is called. Inside the processPacket() function, there is a check to see whether gotPacket is set to true. If it is, the processPacket() function will print out the info.
      If you can explain to me why we have to make this arrangement, you will have understood the code, I think ๐Ÿ™‚

      1. Okay , I’m working with Siwanan Poophat this is my project and i need to use this product immediately. So how long i get it. (Thailand)

        1. Hi Surapat
          With DHL Express shipping, it should not be more than 3-4 business days to Thailand. I ship daily, so you will have the products fast ๐Ÿ™‚
          Kind regards,

    1. Hi EJR
      While I have not tested it with Winlink specifically, it will probably work. One thing that might be a problem is that MicroModem does not have enough RAM to hold a long queue of data to be sent out in its internal memory. If Winlink uses it’s own flow control system, that should not be a problem though. If you need a higher-performance modem, you might want to wait a short while until OpenModem ( is released. It is much more powerful, can handle large amounts of data in queue, and has many new features. It will be available very soon.
      Kind regards,

  68. Hi! Mark now I upload firmware simple serial hex file on my micromodem but when i measure audio output it doesn’t work on ossiloscope ,so what heppend?? what should i do.

    1. Could you let me know the exact link to the firmware file you used? Also, please check that the potentiometer on the modem is set correctly! If it is turned all the way to one side it will be almost silent, and hard to measure on the scope!

        1. and when i connect micromodem to ardunio program ,com port is always busy
          why is this?

          1. Thank you Markqvist I have already fixed the problem, sorry for wasting your time. I will ask you later hahahah

  69. Hi Markqvist
    I love and use your midi Katapult to create a simple lightmap for my launchpad while DJing with serato. It’s the only way I’ve found to create lights while not using Ableton. I’d like to upgrade to the Mk2 Launchpad and would like to pay for your time to make the software work on the new launchpad. Is that something you’d be able to do? I DJ as ‘Hot Dub Time Machine’ ( here’s a photo of the app being used:

  70. HI
    After the realization of several digipeaters based on TW Icom and Microsat digipeater I want to realize an autonomous digitpeater powered by solar panels so very low consumption.
    In addition, the reception site is very used by the vhf and to avoid any remark the reception will remain in 144.8 but the emission (300mw) will be in uhf to my igate.
    To do this I intend to use 2 DRA 818 one in reception and the other in transmission uhf the modules are sold by SV1AFN and already include harmonic filtering and audio.
    In addition to your module must I program 2 micro .. to drive the rx module and tx module?
    ย  Or your module has the ability to drive the 2 DRA, in addition to its function of digipeater.
    Thank you Best regards
    Roger Van Klaveren / 3A2NG

    1. Hi Roger
      You could use two MicroModems connected back-to-back over the serial connection, one connected to each radio module. Or you could use one module connected to both VHF and UHF radio modules, and then use the experimental digipeater firmware. Be aware that you need to configure and compile the digipeater firmware yourself at this point, and that it should still be considered as beta. It is in use several places, but there might still be undiscovered bugs, so be aware of that ๐Ÿ™‚
      Kind regards,

  71. Hello I am the President of umhab (university of Manitoba high altitude club) and we are planning to launch at the end of April. We are planning to use your tnc modem for our diy tracking system. We are using a raspberry pi zero via i2c to make the packets. We we’re wondering if you would like to sponsor our club! Feel free to email me.

    1. Thanks for noting it, something has broken, and I’ll be fixing it

  72. Hi Mark, finally figuring out the git thing and had to stop by and say thank you for the wonderful APRS designs. I made my own castellated version of the micromodem for a larger project I”m working on. Not on the air yet but it works via audio-jumper with direwolf very well.
    I tried to join the forum, but the captcha wouldn’t work? “drag box left to right” worked and let me click ‘register’ but it kept coming back with ‘invalid captcha’

    1. Awesome, thanks a lot for sharing this! Great design!
      Sorry about the forum, something is broken. I’ll get around to fixing it one of these days ๐Ÿ™‚

  73. Hey, Mark! Are you going to have the MicroModem in stock again?

  74. MicroModem wรผrde das mit dem icom 207 der hat eine data buchse kรถnnten sie da schon ein kabel dran machen ?!??!
    MicroModem would do that with the icom 207 which has a data socket could you already have a cable to it?! ??!

    1. I don’t offer a ready-made cable, so you will have to make one according to the pinout of the Icom 207.

  75. Mark, I am working on a video series about APRS hardware and software. Would you be interested in being part of this? Please send me an email and let’s talk. Thanks!

  76. Hi Mark!
    when will be available more micromodem boards on your shop?

  77. Hello Mark I want to participate and want to let you know of an error I received when clicking Register for the form:
    An error was encountered
    Error: Could not connect to smtp host “[server removed*]” (0) (php_network_getaddresses: getaddrinfo failed: Name or service not known).
    * Note: I removed the server name for security purposes from the error copypasta.

  78. Hi, do you expect to have rnodes for the USA ISM (900MHz) LoRa band available again anytime soon? Thanks!
    I ordered some Lostiks with the idea of running KISS or UUCP across them, but it would be fantastic to not have to write software to translate KISS frames into hex-encoded AT commands.
    73 de John KR0L

    1. Hi John
      They’ll be available again soon. I recently moved and had to build a new workshop, so I’ve been unable to produce units for a while. Unfortunately I ran out of stock sooner than I’d anticipated, but I’ll have a new batch ready soon!

  79. Hi Mark!
    Are you still making the RNode(s) at your Shop? I see that the 820-1020 Mhz models are all out of stock.
    Thinking of buying a couple from you (if available) to play with in AU.
    Kind regards

    1. Hi James
      They’ll be available again soon. I recently moved and had to build a new workshop, so I’ve been unable to produce units for a while. Unfortunately I ran out of stock sooner than I’d anticipated, but I’ll have a new batch ready soon!

      1. Hi Mark, No worries! Totally understand. How will we know when you have more stock? cheers James

  80. Hi Mark,
    I like your ideas, was wondering if there is any schedule on having some of the MicroModems in stock? I am putting together some units for a few High Altitude Ballooning payloads and yours looks like the best bet for what I want to do.
    Please update when you can.
    Thanks. Keep up the good work.

    1. Hey K4DW
      Apologise for the long delay. I had the shop closed while rebuilding my website to an updated shop platform. It’s back now, and it’s possible to buy modems again, if you are still in need of some.

      Kind regards,
      Mark / OZ7TMD

    1. Hey Marcel! Thanks for the patience ๐Ÿ™‚ Finally the shop is restocked. Most of the hold-out was actually that I had to rebuild the entire website from scratch. My e-commerce install was so old now, that I really had to get everything up to date. It took a while, but everything is ready now.

  81. Hi Mark!
    Any word on the new RNode batch? I was also wondering if the OSS-7 stack (implementation of DASH7) is compatible with your board? I’m not particularly married to DASH7, I just want bi-directional comms with either mesh or repeater functionality.

    1. The batch is ready, and the shop page is online again after a rather lengthy rebuild! Sorry for the wait! I don’t have any boards that support DASH7 yet, but I will definitely look into it in the future!

  82. Hi Mark,
    FYI – the OpenModem stuff looks super interesting, but there are a number of links that are dead. Just figured you’d want to know! ๐Ÿ™‚
    — Markus

    1. Thanks for the heads up on the links! I havenโ€™t completed writing the pages yet, so thatโ€™s why the links are dead currently ๐Ÿ™‚ They will resolve soon.

  83. Hi Mark,
    I know we’ve been talking back and forth over the months. Wanted to touch base with the latest. Looking forward to hopefully tinkering with OpenModem in a couple weeks when we have school break (I’m a teacher) but we’ll see. I’ve changed the focus of this project a little. Rather than having students build the TNC code themselves, I’m going to go with your image and say “we could build this ourselves the way we’ve made other Arduino stuff, but in the interest of time we’re going to just use the image.” So that’s resolved. (Some of the heavy lifting is about hardware and software, but part of this is what and how I’m going to teach this stuff to students.) The goal is to design a high altitude balloon flight computer that can not only send APRS signals with both position and telemetry, but to also receive signals that can be parsed and sent to the flight computer for execution. At this point, I think the APRS TNC in the balloon will be an Aruduino Uno with an Uno shield. (I’m looking at the Uno because that’s what we use for other stuff, so we have a number of them on hand. A friend has a CNC router, so we can design custom shields in Eagle and mill them. We may switch to something like the Nano in the future as a way to save weight.) The APRS TNC will send and receive signals to/from the flight computer, an Arduino Mega with a custom shield connected to sensors, switches, solar panels, and everything else. So that’s the idea at this point – hoping to keep tinkering and have prototype student kits ready for the fall. Any info or suggestions you would like to share would be awesome! I’ve started putting design notes on a website – happy to share that if you send me a good e-mail address (I’m Thanks! -Markus (K1FIG)

  84. I’m new in this field.
    This is regarding point to point LoRa.

    If I have 5 units of LoRa device that is configured as Point to Point,
    and all of them are within range of its communication range; let say 1km.
    If one unit transmits a message,
    Will the rest receive that message?

    1. No problem, hope this explanation can help ๐Ÿ™‚ Your assumption is correct. If you are using my RNode device, and 1 transmits, while all others are in range, all others will receive the transmission.

  85. Hi Mark;

    What would be the shipping cost of RNode to Denmark ( aalborg ) ?

    1. Hi Rakesh! After updating the site, I had forgotten to add shipping rules from Denmark, so thanks for the reminder! I just did, and you can now select to have it shipped as a PostNord package in Denmark, for 9โ‚ฌ.

  86. Hi Mark

    Ordered 2 of the Rnodes over the weekend for delivery to London, with all of the current Covid issues, any idea if this will impact you for sending out?


    1. Hi Michael
      Thanks for the order. Iโ€™m sending out almost as normal, but the postal service here are a little slower to pick up the packages from me than usual, and also telling me to expect a day or two extra transit for packages within Europe. Your package left here yesterday though, so with a little luck youโ€™ll have it before the weekend.

      Kind regards,

  87. Hi Mark,
    I would like to purchase one of the Open Modem units this summer for use by my students in the fall. Could you e-mail me at your convenience? (I’ve submitted my work e-mail.)
    — Markus

  88. Hi Mark,
    I just saw the MicroModem was replaced by the OpenModem. I had a quick question before I purchase two of them for a project Iโ€™m doing. Does the OpenModem have the same SimpleSerial firmware that the MicroModem had? I wasnโ€™t able to find anything about that.

    1. Hi Sam,
      Good question! Currently it does not, but itโ€™s only a software limitation right now, as the firmware is KISS-mode only for now. Iโ€™m currently wrapping up some work on Reticulum, and will return to work on the OpenModem firmware afterwards, adding features like SimpleSerial, standalone tracking and digipeating.

  89. Does the RNode implement everything required (encryption etc) to be compatible with other LoRaWAN devices?

    1. No, RNode uses raw LoRa modulation, and does not implement the LoRaWAN stack.

  90. Could we make a 2m 144mhz APRS tnc using the RNode?

    I see that the RNode is sold as two different frequency models 410-525mhz and 820-1020mhz however the Semtech SX1276 chip is capable of 137 MHz to 1020 MHz. What’s restricting what frequencies can be used?

  91. Would OpenModem interface with HamShield (1.0/Lora Editions) for a standalone deployment to eliminate requirement of additional external radio?

    1. No, sorry. I’ve decided to stop offering PayPal as a payment method because of the high fees PayPal charges.

      1. But okay, this answer is at least a proof that you still exist. Maybe one can do without the buyer protection

        1. I can assure you that I will ship the products you order quickly and that I will accept returns if the products don’t live up to your expectations.

  92. Hello,
    Do you have any plan to make a similar device using the SX1280 LoRa chip (2,4Ghz) ?

  93. Could this device be made to use pactor for connection to winlink. Maybe using the hfkernel pactor implementation.

    1. It is something I have only been superficially looking into at this point. It might be possible, but I have not looked far enough into the processing/memory requirements of various open pactor implementations to be able to give you a certain answer.

  94. Hi Markqv

    I work for an industrial systems integrator. I am looking for an TCP/IP over LoRa product for CIP messaging to PLCs,and physically plug into a Ethernet switch. Idealy, it would run on 24VDC, be din rail mountable or part of an antenna that you could punch in the outside of control box. I’m only looking for 100 bytes of useful data every few minutes; we could even while list communications between two IP addresses.

    There is a huge market for this stuff. Every water pump station would want one.

    Can you point me in the right direction? You look like you are a stones throw away from something like this.

    1. You are right, it is pretty close. I actually have a completely untested prototype design of an RNode based board with some of the features you mention, but for various reasons I didn’t prioritise testing and putting that particular board into production. Maybe I should take it up again…

  95. Hi there, I have order a RNode last week and my order number is 10875, I wonder that when could i get the DHL tracking number. Thanks!

    1. Hi there! The order was already shipped on saturday and the tracking number sent on the same day ๐Ÿ™‚ Just to be sure I have sent you an extra copy of the tracking mail. Please check your spam folder also!

  96. Hi Mark,
    I’d like to try running the RNode firmware on some Arduino boards with LoRa SX1276-based modules (these ones: Should this work with an Arduino Mega 2560 perhaps even an Arduino Uno board? I noticed that in the Config.h file there’s a #define that only compiles if the MCU is a 1284P. Does that mean the code won’t work on a different Arduino MCU?
    Thank you,

    1. The firmware did actually support the Uno to begin with (there was a #define section for that as well), since that was the first prototyping platform. But due to the RAM constraints on that chip, it’s no longer supported. You could probably port it to the 2560 no problem, you would just need to remap the pins and dial the buffers back a bit to account for it only having 8 KB of RAM instead of 16.

  97. Hi Mark,

    as you know, i used the LibAPRS to realize a classic KISS-TNC like the (Z80-based) TNC2 (

    What i am not able to realize is a code, that decodes the NRZI bitstream instead of the AFSK-tones.
    I`d like to substitute the AFSK.c/AFSK.h by something like a “NRZI.c or FSK.c.

    I looked for a the variable that contains the NRZI bitstream to feed it with the value generated by a digital Pin, that gets its Signal by an external tonedecoder-IC like the TCM3105 but without sucsess ๐Ÿ™

    So my (outrageous) question: Can you or somebody that reads this help me ?

    many thanks by micha – DC1MAK

  98. Hi Mark,
    I am trying to repeat your design. When sending text, PD7 output is high and there is no audio signal to transmit. What could be the problem?

  99. Hello,
    I’ve been interested in getting an Rnode for a while but they were out of stock. I am trying to packet sniff communication between LoRaWAN gateway and an end device. gatways using a Dragino LoRa Shield on a raspberry pi and end device is an arduino with a dragino lora shield. Am I correct in believing this will be able to sniff this traffic and how quickly will you be able to ship it to the UK. many thanks, Tom

    1. Hi Tom
      Yes, you should be able to sniff the traffic. But please be aware that some specific types of traffic needs extra configuration options in LoRaMon. LoRaWAN Class B Downlink Beacons for example are sent in implicit mode, and you will need to specifically tell LoRaMon to listen for this. By extension, if you want to sniff both normal explicit header mode traffic and headerless Class B Beacons at the same time, you will need two RNodes – one that can sniff the explicit-header traffic, and one that can sniff the implicit-header traffic.

  100. Hello,
    I am trying to use your RNode code to SSH over 2 ‘Dragino Pi Hats’
    I cannot get it working. Is it even possible to use this code over the Dragino Pi hats to SSH?

    Thank you

    1. Hello there
      It might be possible to use an RNode firmware and tncattach on dragino boards, but you’d certainly have to port the firmware to the boards. Unless they are using a very similar hardware setup, it will not work as is.

  101. Hello Mark,
    Very cool project! SSH over LoRa, that’s why i became interested in LoRa at all. But so far i didn’t manage to built up such a link. Now i found your page, very encouraging!
    However the modules are very expensive.
    Also, i already own two LoRa hats for a Raspberry, based on the SX1268 (433 MHz), see

    Do you see a chance to adopt the code for this chip and board? Or could it run directly over that device? I’m still a beginner on LoRa.. It would be optimal to run SSH over LoRA on a Raspi that way…


    1. Hi Stefan!

      Thanks for the comments ๐Ÿ™‚ Yes, the modules I sell are expensive, relatively speaking. They are made by myself here in Europe, and the quality control and testing is extensive, and I only use high-quality and genuine components. But he biggest part of the devices I sell are really all the open source software that I write and maintain around the devices. Those things are the value behind the price. So yes, the hardware I sell is quite pricey, but you also get some value for that money ๐Ÿ™‚

      Realistically, I will not spend time on adding support for various external boards, unless it makes a lot of sense for the ecosystem as a whole. But you are very welcome to do this based on the source code on github, if you want to invest the time in it.

      Just let me know if you have other questions!

      Kind regards,

  102. Another question: Does the RNode hardware together with two Raspberry Pi (Buster) NOW, in June 2021, support not only normal ssh but also SCP? File transfer over LoRA 433 MHz would be great, even if it takes a long while…

    1. Yes, SCP works just as well. Just ran a test with two Pis and RNodes transferring some files over SCP and as expected it works as it should. You can also use rsync if you want.

  103. Hello. Iยดm Jose Luis, from the Canary Islands, in Spain.
    I would like to know if you ship to my region and how much are the shipping costs. I ask you this because the shipping costs to the islands may be different than to the mainland. We would assume and manage the costs and customs clearance.
    Thanks in advance

    1. Hello!
      I do ship to Canary Islands, and the shipping costs will currently be the standard 27EUR for a tracked package. You are very welcome to place an order in the shop, or contact me if you have any other questions.

      – Mark

      1. Hello Mark:
        I need to buy 8 units of Antenna SMA: 433 MHz, and I want to know the costs. However, I see on the chekout page a line with EU VAT, but even though we are in Spain, we have a different tax regime and we do not have to pay EU VAT.
        How can I proceed to place the order without taking that fee into account?
        Thank you.

  104. HI. We would like to create a system to monitor a High Altitude Balloon in South Africa( HAB ). We use the 868MHz band here. Can you suggest what components would be needed in order to monitor the balloon of the 868MHz band while in flight?
    I’m thinking a RN node inside the payload with an ‘openmodem’ linked to a packet radio as a groundstation?

    1. You should be able to use just an RNode in each end, in this case there would not be the need for an extra modem and radio!

  105. Hi,

    thanks a lot for this great project !

    I’m trying to initialize the EEPROM on a custom rnode (made on a breadboard) using

    rnodeconf.exe -r COM13

    but I’m getting :

    > Opening serial port COM13…
    > Device connected
    > Firmware version: 1.17
    > Reading EEPROM…
    > Invalid data specified, cancelling EEPROM write

    which data do I have to provide in order to initialize the eeprom ?

    thanks again and Best Regards


    1. Delivery time within Netherlands is usually only a couple of days. You can always see the current shipping rate at the checkout page.

  106. Hi Mark – I see the RNode 820-1020 is out of stock. Any info on when it may be back in stock? Or a waiting list option for the next batch? Thanks!

    1. Hi Jamie
      Yes, getting components shipped is a bit unreliable still, so I ran out of stock on those. Should have materials soon and my guess is stock will be ready to ship on the 26th. I can open pre-orders if you’d like to get an order in already.

      Kind regards,

      1. Thank you Mark – definitely sounds good. I’d be glad to put in an order whenever you are ready.

        1. Thanks, they’re available for order now, and will ship on or before november 2nd.

  107. I was looking at your old MicroModem firmware and it looks like you tried to implement a new digital mode called MP1. I am interested in trying to create my own digital mode for low bps HF. I am designing a radio to go with this

    and I have some documentation of the mode here

    One thing I would like to know is why you decided not to continue with MP1. It seems like there were good ideas in it, for example, FEC and interleaved bits, that perhaps are not widely used because older standards such as Bell 212 are used for packet radio. I would like to create a mode with FEC (extended Golay) and other redundancy for slow but reliable microcontroller-to-microcontroller communication. Perhaps I can learn from your experience.


    Dan KW4TI

    1. Hi Dan
      Thanks for the interesting questions. Yes, MP1 was an experimental general purpose mode I created a while back. I wanted to try a more robust mode for use with an early precursor to Reticulum, and the experiment was somewhat successful, but I the even though the interleaving and FEC did improve packet decoding in presence of interference and with low signal levels, the benefits in practical terms on real-world VHF and UHF channels were not that significant in the end.

      At that point I decided to leave it as an informative exercise and move on to the protocol stack Reticulum, until my skills had developed enough to create an adaptive mode suitable both for HF, VHF and UHF, which is still one of my goals. With Reticulum nearing a complete state, I am starting to move closer to this again.


  108. I had been searching for information on running a BBS over LoRa and found this project. Reticulum and NomadNet are great ideas! I’d like to put these in to use in my town as an emergency communication / local communication network and was hoping it would run on a Raspberry Pi Zero. I’m currently trying to set-up NomadNet on the RPi and keep receiving an ‘Illegal instruction’ error when attempting to run ‘nomadnet’.

    There are a number of friends and local businesses to whom I’d like to give pre-configured Raspberry Pi Zeros w/ LoRa antennae + NomadNet. Solar stations are possible too. Would be so cool and useful to spin-up a community network based on your tech!

    Will more RNode devices be available to purchase soon? Also, will Reticulum work with other LoRa chips (such as RFM95W) as well?

    Thanks for coding cool software!!!

    1. Hi Paul
      Thanks for the appreciation! That is a very useful project, and I’d love helping you get it set up. It should be perfectly fine to run nomadnet on a Pi Zero, I haven’t seen that error before. What version of the Raspberry Pi OS are you running? You should be able to install everything simply by running:

      pip3 install nomadnet

      And then running it with:


      Can you send me a copy of the complete error if there is more? The only thing I can think of at the top of my head is if there is some issue with the new AutoInterface on Raspberry Pis that don’t have any ethernet devices. Is it a Pi Zero W, or one without wireless? The AutoInterface should just disable itself if it finds no suitable devices, but maybe something is wrong. You might try disabling it or removing it from the Reticulum config file. Also, setting the loglevel to 7 in the config might reveal more info. Can you also please try running:

      rnsd -vvvvvvv

      Just by itself? This will start Reticulum alone, and should tell us if the error is happening in Reticulum or in nomadnet itself.

      Regarding device availability, I am making them as fast as I can, and have almost filled all backorders. If you order now, I will probably ship your devices in about three days. Interest has been rising lately, apparently ๐Ÿ™‚

      Regarding other chips and devices, even though it is still unannounced, I have just added initial multiplatform and multitransceiver support to the RNode firmware and tools. This is still very experimental, and does not offer the same bulletproof stability of the official RNodes, but it is now possible to easily install the RNode firmware on homebrew devices based on the SX1276 LoRa chip coupled with an ATmega1284P MCU or an ESP32 MCU. Many more transceiver chips will be added soon. If you feel daring, you can play around with it by downloading the latest version of the RNode config utility and running:

      rnodeconf –autoinstall

      Maybe you already have a device it is working with ๐Ÿ™‚ Otherwise you are very welcome to order any devices you might need, and they will ship very soon. If you want to pay with cryptocurrency, just email me, since the shop is not set up for accepting that automatically yet.

      Let me know any questions you might have.

      – Mark

      1. Hi Mark!

        I tried running the “rnsd -vvvvvvv” command and received the same error: “Illegal instruction”. I am running it on a Pi Zero W. Thanks!

        1. Hmm, that is strange. Just tried running the latest RNS release (0.3.5) on a Pi Zero W here without any problems. Could you give me the first lines of output of running the “raspinfo” command? Just the first section under “System Information”. Also the version reported by “pip –version” would be useful!

  109. Hi Mark,

    Long overdue but finally getting around to contacting you. I am with a small team to use the reticulum stack to create an alternate means of communication to the Internet, with our ultimate goal being to replace it using whatever physical transport is available.

    We are just in the initial phases of the project. I am a retired software engineer with formal education in hardware. I like to tinker and build things and python3 is my preferred scripting language these days.

    Our initial platform is a raspberry pi 4 with my Pirate Box software that includes IPFS and other tools. My Pirate Box project is slowly evolving and the website ( is in transition. There are several Telegram & discord channels for it I can share with you if you are interested.

    What you’ve created is impressive. Our 1st task is to find a way to bootstrap new nodes with a list of other nodes by passing around a list of node & peer IDs in a file. 2nd is to improve the friendliness of the nomadnet client. I think it would be great to create a GUI for it. I see in the code you have that in mind. I also think there is value in the curses based UI for headless operation through ssh, so both GUI and text are good to have, GUI for grandma & grandma to make it easier to use.

    Using nomadnet with the standard gnome terminal yields some odd characters. I loaded [one of] the nerd fonts you recommend (perhaps your guide info should say which should be used) but still see the funky chars. Which nerd font set do you recommend?

    If it were me, I’d create a GUI for nomadnet based on PySimpleGUI. It isn’t as full featured as Qt or Tcl/Tk but is super fast to develop in and is a reasonable tradeoff for the tremendous functionality it provides. Plus it can be a near seamless transition to provide the same look & feel interface via a web browser.

    I just received some LoRa “hat” boards for the Raspberry Pi based on the newest SX 1262 chip. I want to get my hands on some USB versions, but only found one source so far( which I can’t currently order from. The newer 1262 chip is lower power, longer range and I believe will reduce the burden on the host cpu to manage, and probably have a simpler device driver.

    I’m still waiting on the response from the vendor for the 1262 LoRa RPi hat modules.

    1. Hi Thomas,
      Thanks for contacting me! I’ll be answering your via direct methods shortly ๐Ÿ™‚

  110. BTW I’m glad to hear you accept crypto as a payment option. Please email me the list of cryptos you accept and which is your preference. I’ll order a couple of your RNodes to use for testing other LoRa devices.

  111. Hello, I am interested to buy for OpenModem with Arduino for APRS TX and RX, when it will disponible?
    I understand then OpenModem is ready to use.

    Vy 73 Yvan

    1. I am really sorry, but right now, I simply can’t say. Due to the chip shortages globally, several components that I need to build them are completely unavailable currently. I am looking into alternative solutions, but realistically, it will probably be a while before I can deliver on that, since I need to do new PCB designs, have those manufactured and such.

  112. Just found this via reddit today. Looks so epic. Nicely done and thank you!

    1. You are very welcome, and thanks to you too! Hope you find something here that is useful to you ๐Ÿ™‚

  113. Hi, I’m Sergio from Madrid Spain, I would like to understand why in the guide it is indicated as instar reticulum on Android
    There is still a Lora or RNode to connect, is it correct? or it is not necessary and installing reticulum and the SideBand Softare to send messages would be sufficient
    Can it be done while with other Lora Radio or have to be with OpenModem, RNode, Unduino? When you think you can have them?

    1. Hello Sergio
      There is some more info about Reticulum on Android here:

      You can use many different LoRa radios and modems with Reticulum, you do not need to use the ones I have made. You can find info about compatible LoRa radios here:

      At this point, you can install the Sideband APK directly on Android devices, but you cannot connect directly from Android phones to LoRa radios yet. Right now, the Android version of Sideband will only communicate over WiFi, so you must set up a small gateway on your WiFi network that has the LoRa radio connected. Then the Sideband app can use the LoRa radio as well. There is more details about that process here:

  114. Hello!

    Very nice work, a lot of usefull info!
    I like Lora and use it for some links but I have a demand for a bit higher bitrate.
    So is it possible to swap the Lora module of the RNode? I’m looking at sx1233 module…

    1. The firmware would need to have support added for the module, so it’s not directly swappable without any other modifications, but still something that is totally doable.

  115. HI, I’M INTERESTED IN THE PRODUCT RNode. On the site is not available. Is it still affordable? If so, what are the delivery times?

  116. PCB Layout for the MicroModem is not working at the moment.
    Can i download them somwhere else?

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