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. I encourage you to use my PGP key, that is posted in the sidebar on this page!

101 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 :) 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 :)

  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 ;) 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 ;) 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 3.5€, or about 26 kroner. Or you can select “Local Pickup” and pick it up yourself, if you’re close to Ringsted :)

  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 Andrés! 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 :)

  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
    [email protected]

    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 :)

  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 3.5€ without tracking. If you want it as a registered package with tracking, it’s a bit more expensive at 37€.

      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 3.5€ 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 :)

          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 :)

          2. Your package is on it’s way :) And with a little extra surprise :) 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 :) 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 :)

    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 :)

      Still not decided on doing another run of DIY kits, but will post if I do :)

  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 :)

  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 :( 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 :)

  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 :)

      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 información 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!

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