NPR New Packet Radio

IP over 430MHz Ham Radio, up to 500kbps, 20W RF.
Extension for HSMM-Hamnet-AREDN. 100% open-source.

Public Chat
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NPR (New Packet Radio) is a custom radio protocol, designed to transport bidirectional IP trafic over 430MHz radio links (ham radio frequencies 420-450MHz). This protocol is optimized for "point to multipoint" topology, with the help of managed-TDMA.
Bitrate is up to 500kbps (net, effective bitrate).
The radio modem is cheap (~80$) and home-made, with a 433MHz ISM module inside. The modem is connected locally with Ethernet, therefore no specific software is needed on PC.
The modem is easy to build and reproduce.
You can add a DMR radio amplifier in order to achieve 20W radio power or more.
The main usage is an extension of HSMM - Hamnet - AREDN networks.
All the project is open-source : hardware, software, protocol specification.

NPR modems FOR SALE:

Low prices (79$ fully assembled). International shipping.

If you want to discuss about NPR:

watch full screen.


Introduction and
quick start guide
et guide de
démarrage rapide
Advanced user guide (EN & FR)
Modem assembly and programing guide (EN & FR)
Spectrum Occupancy
NPR protocol Specification (EN)

PCB Design (Gerbers, BOM, etc...)

PCB v02 BOM Easy to provision
Total cost ~80 euros
per modem
(Bill Of Materials)
PCB files release note
PCB v03 Cheaper BOM
Total cost ~65 euros
per modem
(Bill Of Materials)
PCB files release note
PCB v04 Old version sold by
Obsolete do not use.
PCB files release note
Add-on SRAM board for PCB v04 only -
PCB files release note
PCB v05 New version for
Fits Funtronics enclosure
(Bill Of Materials)
PCB files release note

Modem Firmware : binaries and sources

Stable version
Beta version
Binary file, band 70cm Binary file, band 70cm
Binary file, band 2m Binary file, band 2m
Release note Release note
Source code Source code

Adobe Portable Document Format - 1.88 MB - 02/23/2020 at 13:23


Adobe Portable Document Format - 1.33 MB - 02/23/2020 at 10:36


octet-stream - 175.82 kB - 02/23/2020 at 09:56


octet-stream - 175.82 kB - 02/23/2020 at 09:56


x-zip-compressed - 5.32 MB - 02/23/2020 at 09:56


View all 31 files

  • 6- Last news, updates

    f4hdk10/20/2019 at 14:59 0 comments

    23rd Feb 2020:

    • New firmware with new features
      • The modem can now drive an external PA with its GPIO port
      • In case of SPI SRAM present (auto detected), the TX data buffer is increased to 128kB instead of 16kB previously. Big improvement of the quality of IP connection.
      • Radio connection establishment time greatly reduced.
      • TX_test feature finally debugged and stable.
    • Documentation updated ("Advanced user guide" and "Assembly and programming guide") mainly about SPI-SRAM, about PTT ouptut, and about firmware upgrade.
    • Important info about SPI-SRAM :
      The RAM of the microcontroller used is too limited to have good performances, especially at Master side.
    • The usage of additionnal SPI-SRAM chip improves greatly performances, especially for Masters, by increasing the TX buffer length, and the SRAM chip is automatically detected and activated with the recent firmware 2020_02_23.
      Modems v02 and v03 already have this SPI-SRAM chip.
      Modems v04 (the one sold by Elekitsorparts-Funtronics up to march 2020) don't have the SPI-SRAM (it's my mistake, sorry).
      You can upgrade the hardware of a modem v04 via adding a SPI-SRAM add-on board.
      In order to determine if you need SPI-SRAM upgrade, read the dedicated paragraph inside the "advanced user guide".
      You can buy these SPI-SRAM add-on boards from :
      - Western-Europe : contact me f4hdk[at]free[dot]fr . Warning, I have limited production capacities.
      - rest of the world : soon available at Funtronics - Elekitsorparts

    20th Jan 2020:

    • Advanced user guide updated, mainly in order to clarify IP config of modems (client modems). Refer to revision history.
    • Important info: The solution 1 for upgrading the RAM (see below) is feasible, with external SPI SRAM. I will provide soon (february) cheap add-on SRAM boards, and a new firmware (compatible with and without this SPI-SRAM). For modems v04 only. v02 and v03 already have the SPI-SRAM, and the future version v05 will have it also.

    1st Jan 2020:

    • Documentation updated (advanced user guide and introduction) : command "TX_test", adding a fan on the amplifier, setting the MTU to 750 for better performances. 
    • Important info : for future features, especially for the Masters, and for improving performances (buffer size), the RAM of the microcontroller is not big enough (64kB). I have 3 options, not decided yet, currently the 3 are under test:
      • Solution 1 (prefered): use the existing SPI-SRAM (23LC1024) of PCB v02 or v03. For PCB v04, I could provide a (very) cheap add-on board, easy to solder on top of the Nucleo. It's a shame that I removed this chip inside v04, I'm very sorry, I thought is was useless...
      • Solution 2: use an external SPI-SRAM in QSPI configuration. The existing PCBs (v02, v03, v04) are not compatible at all, new PCB needed.
      • Solution 3: use a brand new microcontroller (Nucleo L476RG), with a totally new PCB, larger.

    8th Dec 2019:

    • Document "advanced user guide" updated, refer to "revision history" inside.

    26th Oct 2019:

    20th Oct 2019:

    • I have implemented the FDD (Frequency Division Duplex) feature, which is optional. You can now use separated frequencies for downlink and uplink (frequency shift), with one single modem at client side, and 2 modems and a RF duplexer at Master side (one modem for RX, one for TX).
    • New firmware released, and documentation (introduction, and advanced user guide) updated accordingly.

    29th Sept 2019:

    • I have tested the PA (power amplifier) P8X from DF2FQ. Not recommended for use with NPR, because it does not integrate an RX-preamplifier, which is needed in order to compensate poor RF4463 sensitivity. Refer to "Advanced user guide" annex 4.

    15th Sept 2019:

    • Sale is temporarily stopped. A new sale will start end of october, shipping world-wide.
    • New modulations parameters. I switch to GFSK instead of GMSK, with...
    Read more »

  • 5- Planned or possible evolutions

    f4hdk05/12/2019 at 06:26 0 comments

    Please feel free to comment these lists of evolution, and express your requests, or your priorities. Either here or in the public chat.

    Planned evolutions

    • Better FEC algorithm, because currently it is very poor. If you can give me some help, I don't understand a lot standard FEC algo (with all these Maths).
    • Regular temperature check and re-calibration of SI4463 if necessary -> done! (firmware 2019_06_16 and above)
    • Increase to 15 clients instead of currently 7 maxi. → Probably not feasible with current hardware at Master side, not enough RAM (new hardware under study)

    Possible evolutions, if people are interested (raw order, no priority order):

    • Static IP management of some modems → Removed because you can use future "L2 pure ethernet transport feature" which will be more flexible
    • Management via pure serial port (instead of USB)
    • L2 Ethernet transport configuration (instead of currently L3 IPv4); could enable more flexibles topologies, and IPv6 compatibility. But a little bit less efficient.
    • Extension of frequency range to 420-450MHz instead of currently 430-440MHz (IARU region 1 limits) -> done! (firmware 2019_06_16 and above)
    • Other modulation parameters, with lower datarates, in order to decrease RF bandwidth -> Done (firmware 2019_06_16 and above)
    • QoS necessary in order to transport VoIP data over an NPR network
    • Totally new design, microcontroller with more RAM, PCB optimized for automatic PCB assembly line. Goal would be to mass produce fully assembled modems. Probability low, only if enough people are interested.-> Cancelled feb 2020. The current hardware is already "mass produced" by Funtronics - Elekitsorparts
    • Frequencies split between uplink and downlink (in case you use NPR Master in a tower where a UHF FM repeater is already present). Additionally, the Master could be used in "FDD" (Frequency Division Duplex) mode in order to use these 2 frequencies simultaneously, like 2G or 3G mobile phones. 2 modems required at Master side. Complex! --> done! (20th oct 2019)

  • 4- FOR SALE! (New Packet Radio modems).

    f4hdk04/22/2019 at 06:34 0 comments

    NPR modems for sale!
    Low prices (79$ fully assembled). International shipping.

    If you want to sell kits from/to a particular region (either Europe or US or another), then I can add your contact e-mail and website inside this blog post.

  • 3- Firmware history

    f4hdk04/22/2019 at 06:21 0 comments

    for later usage

  • 2- Deployment, NPR networks, tests

    f4hdk04/22/2019 at 06:20 1 comment
  • 1- Pictures

    f4hdk04/22/2019 at 06:19 0 comments

    For later usage.

View all 6 project logs

Enjoy this project?



Cloolalang wrote 4 days ago point

Great Project!  A lot of work to make something cool!

Future possibilities:

Use AX 5043 for the 6 and 4 meter bands?

MIMO experiements

  Are you sure? yes | no

michael-schel wrote 05/04/2020 at 14:33 point

If I could add to wish-list:

1) higher modulation like 8PSK with small roll-off factor of 0.25
2) 1Byte (32Subscribers+Statusbits) for the packet header
4) Adjustable guard intervals for reflection supressions

Are there such chips on the market, or only possible with SDR?

  Are you sure? yes | no

Kosma wrote 04/05/2020 at 09:11 point

Interesting but not mobile. I need small box (offgrid) for baofeng and working 20h per day (or one charged)

  Are you sure? yes | no

dave.roberts wrote 02/07/2020 at 11:06 point

Hi. Trying to rebuild the firmware but the makefile calls for a set of files in mbed-os/features/filesystem, but the folder is missing from the source zip file. Where do I find them?

I looked in github ( but there is no such folder there as far as I can see. There are files with similar names in features/storage/filesystem and features/storage/blockdevice. Have they simply been moved or is this something different?



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dave.roberts wrote 02/07/2020 at 15:04 point

I started copying files to the locations indicated by the makefile then found that it messed up the relative locations of the headers referenced in the files, so then I copied over the frameworks folders needed and started updating the paths in the makefile, only to then discover that there are many other files that need copying. I stopped thinking you must either be using an old version or a different version or I am making a silly mistake.


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RT wrote 01/29/2020 at 02:30 point

Hello, great project! I would like to leverage the 33CM band here in the states to make use of the full potential bandwidth. Can you release firmware to operate in the 902-928 MHZ Range?

  Are you sure? yes | no

thomas wrote 01/17/2020 at 08:18 point

I find it, thanks

  Are you sure? yes | no

thomas wrote 01/16/2020 at 19:35 point

How do I update the firmware from Windows or Linux?

  Are you sure? yes | no

f4hdk wrote 01/17/2020 at 05:40 point

Hello @thomas  I prefer to discuss in the "project chat" here :

Please go to the chat if you want to continue discussion.

Have you followed the process described inside the "assembly and programming guide"? Do you have some difficulties?

  Are you sure? yes | no

ostropest wrote 12/28/2019 at 22:22 point

nice but pygo are cheapest

in my opinion baofeng+soundmodem+linux (tnc, normal server) +power mobility

will be better.

for will be great

  Are you sure? yes | no

f4hdk wrote 12/29/2019 at 06:34 point

You cannot compare "New Packet Radio" and "baofeng + soundmodem". That's not the same goal, the same solution. You will never get 100kb/s to 500kb/s from a "baofeng + soundmodem"...

  Are you sure? yes | no

ostropest wrote 12/29/2019 at 18:52 point

I'm normal user ;)

I need send sms/shor message for friend, read info etc.

My friend have solar panel and live 5-20km near me. The goverment not working, and i have power if sun lighting

  Are you sure? yes | no

dl8ma wrote 12/21/2019 at 11:07 point


I'm looking for the schematic for the NPR-70

73 de Jürgen, DL8MA

  Are you sure? yes | no

Kermit Kong wrote 12/21/2019 at 05:57 point

which RF-Duplexer can be used ?



  Are you sure? yes | no

Erik Finskas wrote 12/03/2019 at 19:46 point

First two kits made it through the Finnish Post strike! Let the building begin!

I am already looking forward of a simple PA design. Does the modem provide a 'PTT' output to drive the TX/RX switch instead of a RF-VOX? That would simplify the PA design a bit. PIN diodes are fast enough and could be driven by this TX information from the modem.

  Are you sure? yes | no

buggbear wrote 01/11/2020 at 20:54 point

I am also interested in this quesion. Anyone figured out if there is a PTT / TX output signal available?

  Are you sure? yes | no

1221102 wrote 11/21/2019 at 04:39 point

Just got my first two NPR modems configured and on the air.  Let the testing begin.

  Are you sure? yes | no

DJ2RF Fritz wrote 11/05/2019 at 16:05 point

Are there any diferents between V3 Boomlist and V4 Boomlist? 73 DJ2RF

  Are you sure? yes | no

harzi wrote 07/19/2019 at 06:58 point

Dear Guillaume
I am using FW 2019_04_06 and have one master and two clients working without booster properly.

The gotechnique-booster weren't switching fast enough from RX to TX, but are transmitting also by the clients (anyhow, they have been withdrawn in newer guides as working compatible with NPR).

The booster VR-P25D (UHF) works only on the master. 'set RF_power 8' and higher let the VR-P25D transmit. Lower values 'RF_power 7' or less turn the booster TX off. The level is similar as the gotechnique-booster.

Unfortunate the two clients aren't able to switch the VR-P25D booster to TX. I also tried 'radio off' and 'TX_test', without success.

Do you have any advise? Does the new beta FW help and is it stable enough?

Best regards, HB9GVD

  Are you sure? yes | no

IZ7BOJ wrote 04/13/2019 at 12:22 point

Hi Guillaume, I’m following NPR since the beginning, but I didn’t find any useful detailed study about that before your nice article.

I practiced packet radio for many years, I’ve built several S53MV wide-band radios, experimented TCP-IP over ax25 and I regret that period!

Now I’m very excited about NPR. I’m trying to involve other local OMs in order to build a small experimental network.

Thinking in a “daydreaming way”, IMO one limitation in the protocol could be the maximum number of clients (7).

What appens to the 8th client which send a connection request? Just receive a reject like the AX25 “BUSY”? Then the user should periodically retry until one of the clients disconnects from the master?

Best 73’s

Alfredo IZ7BOJ

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f4hdk wrote 04/14/2019 at 06:54 point

Thanks a lot Alfredo for your feedback. 

Answer to your question : if a 8th client tries to connect, then it receives a "NACK" (reject from the Master), and the client modem tries periodically (every 15 sec) to send new connection request, and therefore it will automatically connect as soon as a "client slot" is free.

Initially, my idea was that each client should use its connection for a short period of time (several dozens of minutes) each day. It is currently not designed for 24H/24 connection.

But if there are lots of demand, I will think about increasing this limit to 16 or 32 clients. I will need to make software modification at Master side only.

  Are you sure? yes | no

stevewilliam007 wrote 04/12/2019 at 07:36 point

I have been searching for the packet radio and recently heard from about the newly releasing packet radio which has helped me a lt. There are several latest technologies which are trending in the market.

  Are you sure? yes | no

f1rzn wrote 04/05/2019 at 08:32 point

Ca fait des années que j'espère quelquechose dans ce style, qui nous redonne les mêmes possibilités que le packet radio mais en version moderne. Je me suis permis de partager sur le groupe AREDN (le successeur de BBHN) et sur 2 ou 3 autres pages. Ca me parait très complémentaire de l'AREDN. Franchement bravo et merci. J'espère qu'un jour on aura un satellite geostationnaire qui viendra compléter les possibilités terrestres que cela offre. Ca manque un réseau mondial de données radioamateur.

  Are you sure? yes | no

f4hdk wrote 04/05/2019 at 12:27 point

Merci beaucoup pour ton retour. Préviens-moi si tu veux tester cette solution. Tu as mon e-mail si besoin : f4hdk[at]free[dot]fr

  Are you sure? yes | no

F4HZO wrote 04/03/2019 at 20:06 point

Super ce système cela offre des possibilités inédites en matière de couverture Hamnet surtout pour les communications d'urgences !

Merci de partager la connaissance !!

Meilleurs 73 de Florent F4HZO

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f4hdk wrote 04/04/2019 at 17:17 point


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bferrell wrote 04/03/2019 at 19:58 point

In regards the 433Mhz ISM module, Adafruit has one for just a bit under $10 US

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DL4APT wrote 04/03/2019 at 12:06 point

if i find the time i will look into modifying the design to use this much cheaper Ethernet module (same chipset but less then 4€ compared to the 20€)

  Are you sure? yes | no

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