NPR New Packet Radio

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

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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?



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

Ken N8KH wrote 03/27/2019 at 02:47 point
I have not yet received an answer to my question: are kits available. Are the motherboard (and daughterboards) available for purchase? How much??

  Are you sure? yes | no

f4hdk wrote 03/27/2019 at 04:23 point

Hello Ken. I'm only a hobbyist, I have other things to do in my life, that's why I don't reply rapidly. Please be patient.

About kits, I don't know if I will be able to ship outside Western-Europe. If someone in the US can organize that for US people, it would be great. 

The price for one modem kit is about 80€ here, plus shipping.

Please send me an e-mail to f4hdk[at]free[dot]fr and I will keep you informed. But once again, you will have to be patient, it will take weeks, months to organize that.

  Are you sure? yes | no

Ken N8KH wrote 03/28/2019 at 02:24 point

I'm very interested in this project, and also helping you to write software and/or develop hardware.  I've been interested in high-speed data radio for about 2 decades or more.

I've also looked into the Silicon Labs chip-sets in the past, and found them very interesting.  I'm glad to see that you've taken my ideas with Silicon Labs chips farther than I ever did.

  Are you sure? yes | no

k0elr1 wrote 03/28/2019 at 00:03 point

I wouldn't get too excited about this. By my reading of the US rules (specifically, parts 97.305(c) and 97.307(6), data transmissions are limited to 56 kilobaud and 100 kHz bandwidth in the 70 cm band. I could be wrong, but I'd check before I ordered anything.

  Are you sure? yes | no

Ken N8KH wrote 03/28/2019 at 02:21 point

> data transmissions are limited to 56 kilobaud

> and 100 kHz bandwidth in the 70 cm band

You are correct.

But it is a stupid rule.  It should be rescinded.

And I understand that it is fairly easy to get an experimental license to operate in (or out of) the amateur bands.  So it could be used under an experimental license.

  Are you sure? yes | no

robert.ehresman wrote 04/01/2019 at 21:02 point

Gentlemen, I direct you here for the 2005 ARRL legal brief position on broadband data transmissions in 70cm as they interpret CFR 47 Part 97.3 FCC regulations.

Read it yourself, of course, but the summary conclusion by the League legal team is that if a data transmission method MAY be used to carry encoded video combined with other information (whether the video is actually present or not) the FCC would therefore classify the emission as Amateur Television, and the allowable transmission bandwidth can be at least 9 MHz on amateur allocations above 420 MHz. I am aware there are some groups and individuals in the US that have been operating HSMM or Broadband Hamnet style 802.11 based mesh radios in the 70cm band (radios by Xagyl or Doodle Labs) for years. This has probably never been tested in court or as far as I know any sort of enforcement action mind you, but that is why we have the League and why they established such a position at the beginnings of HSMM. Regionally there may be a conflict with common practice such as properly coordinated ATV repeater coverage. I believe effective video teleconferencing has been accomplished at rates well below 500 kbps for decades. 

  Are you sure? yes | no

cottsak wrote 03/26/2019 at 06:10 point

What's the point-to-point tested range and some throughput data for said test? Also do you have images of the antennas?

  Are you sure? yes | no

f4hdk wrote 03/27/2019 at 05:45 point

We have not tested maximum distance for point to point links. But you can achieve big distances with high gain Yagi antennas at both sides of the link. 

  Are you sure? yes | no

Ken N8KH wrote 03/28/2019 at 02:22 point

My napkin calculations about a decade ago resulted in about a 25 mile range for two stations with 200 kHz bandwidth, 20 W each, and a vertical omni-directional antenna with about 6 dB of gain, and some moderate feedline loss.

  Are you sure? yes | no

f4hdk wrote 03/28/2019 at 13:04 point

@Ken N8KH  about your distance calculation...

Warning, omnidirectional antennas are hard to use at such high Symbol Rates (up to 500kS/s), due to "multipath" issues. You should prefer directional (Yagi) antennas, at least on one side of the link (client side). I will probably add explaination about that inside the documentation. 

If you want to discuss more about that, do not hesitate to switch to the "public chat room" of my project. 

  Are you sure? yes | no

Ken N8KH wrote 03/26/2019 at 03:35 point

Are kits available for the modem?

  Are you sure? yes | no

shawn wrote 03/25/2019 at 16:38 point

I see you mention a kit in your presentation.  Count me in if you are trying to gauge overall interest.

  Are you sure? yes | no

Stuart Longland wrote 03/24/2019 at 09:05 point

How wide are the channels to produce 500kbps data rates?

  Are you sure? yes | no

f4hdk wrote 03/24/2019 at 09:22 point

Hello, you can refer to the table on page 18 of the "introduction document": RF bandwidth is 750kHz for 500kbps of net-effective datarate, over a 1Mbps channel. It is similar to DATV SR-500kS/s. Like for DATV, we use directional antennas.

  Are you sure? yes | no

Erik Finskas wrote 11/13/2019 at 10:40 point

Are the RF bandwidths similar on GMSK than with GFSK? The documents refer to GFSK but I understood the v2 protocol uses GMSK



  Are you sure? yes | no

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