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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.

In the 1980's Packet was developed as a more up to date version of RTTY, with the similarity that both RTTY and packet are digital communication modes and both capable of one to one communication the difference is Packet was capable of storing messages in mailboxes.

Some Packet is still in operation today April  2014 so where in the paragraphs the past tense is used please now consider it in the present tense!!

Being a digital communication, the information is sent is small packets and required a TNC (Terminal Node controller) to both send and receive the packets.

  • Packet radio had many advantages over other digital modes such as:-

  • Error correction

  • one frequency to handle more than one contact at a time

  • messages could be pictures, text and even software

  • and messages could be stored and forwarded to you from a mail box.

Packet radio use a computer linked to a TNC. The operator typed the message into their computer, the TNC divided up the message into suitable sized "packets" and added to the Packets checking characters and callsigns. The TNC then converted the data into audio tones suitable use by ones transceiver via the mic socket, or data socket if provided.

If the station you wishes to message was in range of your station then you would "connect" to that station and messages could be sent back and forth just as messaging on the internet is done to day.

You could also message station out of range as shown below with stations acting as digipeaters and sending your "connect" message to the distance station. when connected then the messages could again flow back and forth but a delay was experienced if many digipeaters were used.

In fact few messages were sent directly and most were sent via a MAIL BOX SYSTEM. Such Mail Box Stations were allocated a special callsign starting GB7 (in UK) which took your message and stored it for later onward transmission when the intended recipient called the mail box to collect their messages.

As the diagram below shows the packet system can be vast but is now being superseded by the internet.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 messages sent to your callsign-1 would then not try to display them  but simply stored them 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 wanted to send a message to was in the location of another mail box, the system then automatically sent the mail onward to the local mailbox which the other 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 and it reached automatic world wide linking of mailboxes.

DX Cluster Network

Developed by Dick Newell, AK1A during the late 1980's, PacketCluster™ software became the most popular and exciting way for Ham Radio operators interested in DX'ing (working the world) to exchange DX-related information.

One station is set up with DX PacketCluster and is linked to one or more other stations who have installed the software. These nodes when connected are called a cluster. Clusters are connected to other clusters, expanding the network. Individual users connect to the nodes on a frequency different from what the node stations are linked on. Users are capable of announcing DX spots and related announcements, sending personal talk messages, sending and receiving mail messages, searching and retrieving archived data, and accessing data from information databases, among other features.

Today the Internet has greatly augmented the way a DX Cluster network operates and handles most of the messaging that was previously used by amateurs around the world..



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