About a year ago I purchased 3 NPR-70 Modems. The “New Packet Radio” modem if you will, was developed by Amateur F4HDK and allows you to easily facilitate TCP/IP communications over Amateur Radio with options for various speeds. While the modems are capable of 500kbps due to CFR 47 Part 97.3 FCC regulations in the United States we are limited to 100kHz and 56kBaud. Thus putting our speeds closer to 65kbps.

Still, 65kbps is nothing to sneeze at when your options for TCP/IP communications over Amateur Radio have been limited to packing up AFSK AX.25 frames over 1200/9600 baud connections or having to setup point to point links. Up until now there really hasn’t been many options to do this.

So, what can you do with 65kbps? Why not try to play some classic video games?

I tested this out with Unreal Tournament 99 Demo, Unreal Tournament 2004 and OpenRA an open version of WestWood’s RedAlert series. UT99 and OpenRA did the best at around 100ms ping times throughout gameplay while UT2K4 gave an average of 201ms ping. Still, these are perfectly playable (especially if you grew up in the land of dial-up internet)

So, how do we get this all set up?

Essentially you need to have a router and two NPR modem’s to pull this off, for my experiment I just used the router on my home network and disabled DHCP on my Modem’s to ensure that I couldn’t resolve domain names thus making it a bit easier to connect to the services I wanted to without clogging up the works too much, although yes… A dedicated router would be best.

When connected via USB you’ll be presented with a serial interface at 921600baud. Connect an NPR-70 modem to your computer via usb and to your router via ethernet and connect to your serial interface.

You’ll want to adjust these values to match your subnet but essentially it goes like this.

set frequency 433.500
set modulation 20
set RF_Power 7

set callsign yourcall_0
set is_master yes
set DHCP_active no
set telnet_active no

set def_route_active yes
set DNS_active no
set modem_IP
set IP_begin
set master_IP_size 29
set netmask


Then for your client, do the following.

set frequency 433.500
set modulation 20
set RF_power 7

set callsign yourcall_1
set is_master no
set DHCP_active yes
set telnet_active no


Once everything has a few moments to connect you can use the “who” command on either NPR-70 modem to see if they are connection to each other properly, if so you should then be able to ping the master or any other IP on the subnet from your client computer.

Now you should essentially be able to set up any TCP/IP client/server application you wish. Including some classic video games!

Unreal Tournament ’99 Demo on 433.500MHz

NPR-70 Modem communication

More details on these can be found here: https://elekitsorparts.com/product/npr-70-modem-by-f4hdk-new-packet-radio-over-70cm-band-amateur-radio-packet-radio