Now if I had a real license, I would have a real call sign, in this case I don’t so I will be making some up for both machines. With both “TNC”’s running and ready to go, we need to setup both machines with call sign’s. There are a few unfortunate downside however, The packet size MTU of this makeshift TNC is limited to around 89 bytes do to the ESP’s SDK being limited to sniffing the first 128 bytes of a 802.11 frame, You should improve this later on to implement fragmentation, but unless you add another tunnel on top, TCP is not going to work. I wrote up a small TNC that actually uses 802.11 as a transport for frames to order to play around with AX.25 networking, You can find the code and instructions to build on my GitHub: In fact the protocol is very simple, It has 4 special signalling characters but 3 of them be used to escape the 1st ( the end of packet character ) The protocol I decided to implement was called KISS. These devices have the ability to do raw frame transmission, and they also have promiscuous mode that allows you to “sniff” raw 802.11 packets on a WiFi channel. Here is where the small, tiny and very cheap (3.5$ each for the units pictured) “Internet of things” device comes into the picture. However I don’t have a amateur radio license ( though I should probably get one ) and so I don’t have a TNC nor can I transmit on the bands that APRS uses.

To my surprise it was possible on a modern Ubuntu 17.10 linux install to get ax.25 abilities to work painlessly, a simple sudo apt install ax25-tools was needed to get the basic utilities and I was good to go. Linux itself has had the ability to send and manage AX.25 packets for quite a while, either using the concept of a sound modem using the concept of a sound modem, or using a device called a TNC to modulate and encode APRS packets.

The majority of this traffic however is either weather or location updates, but this is not all of the protocol can do inside it is also the ability to carry IP packets.

It’s amateur radio derivative AX.25 is getting along pretty well with a reasonable amount of AX.25 traffic happening in the UK every single day:Ī view from aprs.fi, highlighting hotspots of AX.25 activity I love obscure protocols, and while most of the world’s legacy X.25 equipment is slowly being shut down.

Wireshark ubuntu 17.10