Internet services over Radio
Winlink Global Radio Email is a ham radio network which ensure simplified Internet E-mail services (but also other useful services, like WX or info bulletins) in locations where Internet access is not available, by using radio protocols over amateur radio bands (HF/VHF/UHF). Overall, this network consists in three layers:
1. The Core layer, called CMS (Common Messaging Server) and having the bridge role between various Internet and ham radio services, like SMTP E-mail or APRS. The communication in this layer and with the next one are done over the Internet protocols;
2. The Gateway layer, consisting in lot of ham radio nodes, spread all over the world, called RMS (Radio Mailing Server), which ensure the bridging between ham radio clients (over radio protocols) and the CMS core layer (over Internet protocols). If a RMS node runs in an area with no Internet access, will become a Relay RMS, providing the radio link from the user client to the RMS node connected via Internet with the CMS;
3. The Radio Clients layer, using various software messaging applications and protocols on their computers and interfaced with the radio transceivers, in order to access the RMS or Relay-RMS nodes, the gates to the CMS core. Sometime, when Internet is available for radio clients, they can use the same applications to connect directly to the CMS, bypassing the gateway layer and using the Internet access.
The aim of this post is exactly this last layer and how to send E-mail messages without having Internet access. In the posts about APRS Services, is described a simple way to exchange E-mail messages, using APRSlink, which, actually, is an extension of Winlink, being designed to work over VHF/UHF APRS frequencies. Why? Because the higher speed (9600 bps) provided by these bands, over reliable short range FM radio communication, allows a sort of acknowledgment (confirmation) of the service commands, while APRS is an unconnected packet protocol which broadcast AX.25 radio frames to all listeners on the frequency.
APRSlink, as a service, in HF bands, due to the reduced reliability and speed (300 bps) is basically unusable and need to be replaced with something based on link connection, within the client and the server are able to exchange acknowledgements. And this functionality is ensured by the Winlink Express application, which includes many radio protocols, allowing working in both HF and VHF/UHF bands.
On the other hand, why choosing a slow radio communication channel instead a faster one? First, because there are many large areas without a good APRS radio coverage. Such situations can be encountered in a portable or SOTA activities, where mobile data is not available. And second, reliable VHF APRS nodes are located in the near vicinity and, in case of a major bad WX or a natural disaster in the area, it is very probable that these nodes to become unavailable. So, HF become a good option in such emergency situations, being possible at least 1000 Km radio links.
So, let's get to work. Start by installing the Winlink Express application, using the package available on the main Winlink Express page.