27 Nov 2021

I have modified the "advanced user guide". The "command list" table inside annex Annex-1 was totally messed up; now it is ok. Sorry for that.

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:

• Modems are back for sale! Kits or assembled version. International sale. Low prices (79$ fully assembled). https://www.elekitsorparts.com/product/npr-70
• I have written an article on IEEE-Spectrum

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 double deviation (compared to GMSK), because radio sensitivity is greatly improved (4dB or more). The radio chip that I use is too bad for GMSK, much better for GFSK, refer to (french) discussion here. WARNING: the new modulation parameters are not compatible with previous ones. Radio bandwidth can be increased, refer to new documentation.
• New firmware released with lots of features : new modulation parameters, frequency resolution improved to 1kHz, Frequency shift feature (currently useless), and new command "version". Refer to release notes.
• A new dedicated firmware is released for 2m band, with the same source code. (mainly for UK). 
• For your information, the next part of the development will be the "Frequency Division Duplex" feature, with 2 modems at Master side (one for RX, the other for TX), plus one RF duplexer.

9th July 2019:

• NPR kits are now for sale at https://shop.thinkstack.de/en/ham-radio/20-new-packet-radio-npr.html (Europe only)

16th June 2019:

New firmware with 3 new features. Documentation updated accordingly.

• New modulations (11, 12, 20, 21) for lower datarates, lower bandwidth. Symbol rates: 56kS/s (complies with FCC) and 120kS/s.
• Frequency range extended to 420-450MHz instead of previously 430-440MHz
• Periodic SI4463 temperature check, and chip re-calibration if delta temperature above 15°C.

2nd June 2019:

• Compatibility of DMR RF amplifier "gotechnique.com" set to "NO" inside "advanced user guide".
• 1st tests of VoIP over NPR. Good in most condition, surely because I have a router with QoS at Master side. Would be better with true "QoS" inside NPR modems.

14 may 2019 :

• Horizontal polarization recommendation removed from documentation (because IARU do not recommend anymore particular polarization)

12 may 2019 :

• introduction of new PCB design v03, cheaper. (The version 02 can still be used)
• New blog post "planned and possible evoltutions"