New subject: ?==?utf-8?q? NPR (New Packet Radio)

15 Sep 2019

Hello,
Here are some news about NPR - New Packet Radio.
I have made a big update of the firmware. Check it here:
https://hackaday.io/project/164092-npr-new-packet-radio

The main evolution is a great improvement of the radio sensitivity. If 
you have noticed lack of sensitivity, it will help, for sure!
In fact, I have switched to GFSK instead of GMSK, with double frequency 
deviation compared to GMSK.
After studying it in details, we have concluded that the radio chip that 
I use (SI4463) is quite bad at GMSK demodulation.

This evolution makes it (of course) not compatible with previous 
version! You have to update all your modems at the same time.
The bit per hertz ratio decreases, and I managed it like this:
  * for low symbol rates with bandwidth constraints, I remain in 
existing constraints (100kHz for modulation 20, 200kHz for modulations 
11 dans 21)
  * for higher symbol rates, the SR is the same than before, and the 
radio bandwidth is increased.
Check all new version of documentation, release notes, etc...

Other improvements:
  * I now publish a firmware for the 144-148MHz band (you need adequate 
radio modules of course).
  * Frequency setting resolution is improved to 1kHz (instead of 
previously 40kHz).
  * RSSI is now displayed in "dBm"

The next step of development will be frequency shift and FDD (Frequency 
Division Duplex) feature. The uplink and downlink frequency could be 
different, and you will be able to install 2 modems at Master side (one 
for RX the other for TX) plus a duplexer. The main goal is to be able to 
locate a NPR Master (repeater) in places (towers) where shift repeaters 
are already present.

Finaly, about the kits sale, a new world-wide sale will probably start 
before end of october. I will keep you informed.

73,
Guillaume F4HDK