NPR New Packet Radio

IP over 430MHz Ham Radio, 50 to 500kbps, 20W RF.
Extension for HSMM-Hamnet-AREDN. 100% open-source.

Public Chat
Similar projects worth following
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 50 to 500kbps (net, effective bitrate), depending on the RF bandwidth chosen.
The radio modem is cheap (~80$) and home-made, with a 433MHz ISM module inside (flexible enough to be tuned over the whole 420-450MHz band). 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.

Note for USA: Due to CFR 47 Part 97 FCC regulations, for the 70cm amateur radio band (restriction to 100kHz and 56kBaud), only the setting "modulation 20" of NPR-70 seems to be legal in USA. Please always check your local amateur-radio regulation before buying and using NPR70.
Modulation 20: Symbol Rate 50kS/s, bandwidth 100kHz, raw datarate 100kb/s raw, usable datarate 65kb/s.

If you want to discuss about NPR:

watch full screen.


Introduction and
quick start guide
v3.6 English
et guide de
démarrage rapide
v3.6 Français
Advanced user guide (EN & FR) v2.14
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 - 1.66 MB - 06/29/2020 at 10:00


Adobe Portable Document Format - 1.66 MB - 06/29/2020 at 10:00


Adobe Portable Document Format - 1.91 MB - 06/29/2020 at 10:00


x-zip-compressed - 5.29 MB - 06/29/2020 at 09:39


octet-stream - 176.08 kB - 06/29/2020 at 09:39


View all 35 files

  • 6- Last news, updates

    f4hdk10/20/2019 at 14:59 0 comments

    29th June 2020:

    • Important firmware update about Ethenet mode configuration 10Mb/s or 100Mb/s, half or full duplex; it can solve a recurrent problem of packet loss and low datarate. Refer to the new version of the "advanced user guide". Many thanks to Kevin M0AHN who discovered the origin of the problem. 
    • Inside Advanced user guide : New recommendation added about daily reboot for modems which are ON 24H/day.

    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: ...

    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?



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

  Are you sure? yes | no

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


[this comment has been deleted]

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


  Are you sure? yes | no

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

  Are you sure? yes | no

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

Jackson wrote 04/03/2019 at 03:56 point

The DMR radio amplifier is available here:

Up to 40W output, really powerful

  Are you sure? yes | no

Richard Green wrote 04/02/2019 at 21:45 point

I'd like to experiment with this in the USA.  I can't seem to find a source for several of the critical parts.  Farnell has a subsidiary nearby, called Newark Element14, and all the small parts are available there.  The PCB I can get manufactured locally.  But two of the modules seem to be unavailable.  The itead LM2596 voltage regulator module is listed as 'Retired' on their website, and I have not found any source for the RF4463 F30 module at all.  aliexpress carries a 'demo board' carrier for it and similar, but not the modules themselves.

If I can find sources for the parts, I'd consider doing a mass order, and making up kits to sell at the big Hamvention next month.

I do have one concern about the protocol itself.  For the most part, NPR concerns itself only with the Physical and link layers, but why does it also act as a DHCP server?  Why not keep it pure and leave that to the IPv4 router?  And allow other protocols (ICMP, IPv6) as well?

  Are you sure? yes | no

f4hdk wrote 04/03/2019 at 03:23 point

LM2596 module is available here (and many other places) :

RF4463F30 :


About your last question: a NPR client acts as a DHCP server, because inside a NPR network, IP are assigned dynamically among clients, and the protocol do not carry Ethernet overhead but diretcly carry IP packets (therefore DHCP is not relevant in the radio part). I plan to allow "static IP" assignment for clients, but I don't know when I will be able to program it., and/or if the small microconrtoller will have enough ressources. 

  Are you sure? yes | no

Richard Green wrote 04/03/2019 at 13:25 point

OK, I'm beginning to get it.  I ran into this once before with an external Wifi-Ethernet bridge called a 'game adapter' which did not carry ethernet MAC of the client across the Wifi link, but chose proxy ARP with its own MAC instead.  Therefore, DHCP server on router would only hand out a single IP lease. Not suitable for multiple client machines at remote end.

  Better to carry full ethernet header within NPR.  More overhead, but more universal application.

  Are you sure? yes | no

f4hdk wrote 04/03/2019 at 16:16 point

@Richard Green With NPR,  can of course put several IP machines (PCs) behind one single client modem. Just set 'client_req_size' to more than one. Take a look at "advanced user guide", especially 'annex 5' and 'chapter 6.2'.

  Are you sure? yes | no

Richard Green wrote 04/03/2019 at 16:29 point

Yes, I saw that.  I still see that as a workaround, a hack, rather than a simple, standards-compliant solution. It would be far better, more adaptable, more universal, if NPR functioned as a fully transparent network bridge in the ISO sense.

  Are you sure? yes | no

RipperFox wrote 04/08/2019 at 02:14 point

About the microcontroller: Ever thought about using an ESP32? I think they are  cheaper and even faster + come with WiFi, wired ethernet can be added with a 1€ board (see e.g.
Thanks for your project!

  Are you sure? yes | no

DL4APT wrote 04/03/2019 at 10:40 point

Nice RF has an aliexpress store: and they also have the RF4463F30 on sale (a lot of them just don't use a space in the name an the search will find a lot or go on the nicerf store to the menue point silconlabs)

  Are you sure? yes | no

Daniel Roseman wrote 04/01/2019 at 01:11 point

Question for you. Does this protocol pause to identify itself? If so, how? What happens if I don't 'set' the callsign in the firmware? I read all of the docs, and I can't find where it identifies itself to the world at large.

  Are you sure? yes | no

f4hdk wrote 04/01/2019 at 04:37 point

Sorry, I'm not sure that I understand the question "Does this protocol pause to identify itself?" English is not my native language.

You can find some answers in the "protocol specification", paragraph 6.3.

  Are you sure? yes | no

Daniel Roseman wrote 04/01/2019 at 20:59 point

Under American law, Amateur radio stations have to pause and identify themselves at least every ten minutes. 

47 CFR § 97.119 - Station identification.

  Are you sure? yes | no

f4hdk wrote 04/01/2019 at 21:04 point

OK Daniel. The NPR modems transmit their callsign (plus the callsign of the peer modem) every 2 seconds. The callsign can contain up to 13 characters.

Do you think that it's enough reguargind the US law that you mention?

  Are you sure? yes | no

robert.ehresman wrote 04/01/2019 at 21:47 point

I do not believe the Who message as described in 6.3 would be compliant station identification in the US. Station identification requires inclusion of the Call Sign. While quite useful, the Who message information would also not be legally necessary here.

Sorry I was typing this while you answered Daniel. 13 characters would be sufficient.

But it sounds like the specification needs an edit.

  Are you sure? yes | no

f4hdk wrote 04/02/2019 at 03:19 point

@robert.ehresman I do not understand your point. Why do you think that the WHO feature of my "New Packet Radio" is not compliant? It already includes the callsign. Refer to §6.2 of the spec also.

  Are you sure? yes | no

fabian wrote 03/31/2019 at 18:19 point

please add linux. And mobile power 24h/365 day

  Are you sure? yes | no

f4hdk wrote 03/31/2019 at 18:46 point

The modem is OS independant. It connects to a host (PC) via Ethernet. Therefore, it is already compatible with Linux.

Have you read all the documentation?

About "mobile power 24h/365d", I have not understood what you expect. Please clarify that.

  Are you sure? yes | no

fabian wrote 04/01/2019 at 11:06 point

comaptible != linux inside and power offgrid

  Are you sure? yes | no

Similar Projects

Does this project spark your interest?

Become a member to follow this project and never miss any updates