Bredhurst Receiving and Transmitting Society

Syllabus Sections:-

8a Packet Radio

8a.1 Recall that Packet radio transmits messages in data format that can be received directly, stored in a mailbox for reception at a later date or forwarded through a network of mailboxes.

Understand the difference between store and forward mailboxes and digipeating.

Packet is a more up to date version of RTTY in that it is communication. Whilst still a digital communication the information is sent is small packets and required a TNC (Terminal Node controller) to both send and receive the packets. As the diagram below shows the packet system can be vast but is now being superseded by the internet.

Packet received directly the beige arrows

The Packet network has developed since it introduction in about 1982. You can make contact one station to another by the sending of a message that was read immediately on the screen of the other station.

Packet digipeating the stations above with BLACK ARROWS

Also your TNC, if your were in a prime location could be set up to "digipeating. The effect of this was that others could "route" message through your system and similarly you could route messages through other digipeaters. When your system received a message that was for digipeating it send it onward without storage.

All you needed to know was where the digipeaters was and this you learned from watching the packets on the screen of your computer. The callsign of a digipeaters would, like the mailbox ,be the callsign-2 for instance. You would send a message such as C M0FSH via G6YLW-2 the C meaning connect and via meaning by using the digipeaters G6YLW-2 .

If the station of M0FSH responded then the reply message would come again automatically via the digipeaters . On your screen you would see "connected to M0FSH". You would then be able to carry on a QSO until you wanted to stop when you sent a message of "DIS" which told your TNC to disconnect you and the link dropped.

This was a very long winded way of sending messages as each time the "via" TNC had to listen to the message and then send it on. When there was a lot of "traffic" messages could get lost and the link often broke down.

So digipeating was on a one to one basis.

Packet stored in a mailbox the Red arrows

If that station was not available then the TNC (terminal node controller) had a small store facility that the user could set up to receive messages that were put into their own personal mailbox. To do this usually meant that you set up your TNC with another other callsign such as your callsign-1. The -1 indicated that this was your mailbox on your machine. Any message send to your callsign-1 would then not try to display it but simply stored it in your mail box.

Packet Store and forward mailboxes.

It soon became apparent that an improvement to the system was needed and this occurred with the provision of the Store and forward mailboxes.

Rather than direct one to one contact you sent a message to your local mailbox which if the station to whom mail was address used that mailbox then it stayed in the mailbox until that station "connected" and then was told Automatically that mail was waiting. They could then read their mail.

If however the station you want6ed to send a message to was in another mail box the system sent the mail onward to the local mailbox that the station could access.

It took some years for the system to develop so that it knew where stations were and soon links to mailboxes outside UK were occurring.

All this happened before the advent of the Internet where now similar sending or message occurs.