Page 152 - DCAP311_DCAP607_WIRELESS_NETWORKS

Wireless Networks

Notes Select a Wireless Antenna: If the bridge you selected does not already have an integrated antenna
you will need to choose one now. For point to point links we suggest a directional panel, grid or
solid parabolic dish antennas.
Peripherals: You will need to select the appropriate lightning arrestors and RF antenna cables to
get you connected and protected.
Double it: Now double the amount of hardware you selected so that you have the identical setup
on both sides.

9.5 Packet Radio Networks

Packet radio is a form of packet switching technology used to transmit digital data via radio or
wireless communications links. It uses the same concepts of data transmission via Datagram that
are fundamental to communications via the Internet, as opposed to the older techniques used by
dedicated or switched circuits.
Packet radio is a particular digital mode of Amateur Radio (“Ham” Radio) communications
which corresponds to computer telecommunications. The telephone modem is replaced by a
“magic” box called a terminal node controller (TNC); the telephone is replaced by an amateur
radio transceiver, and the phone system is replaced by the “free” amateur radio waves. Packet
radio takes any data stream sent from a computer and sends that via radio to another amateur
radio station similarly equipped.

Did u know? Packet radio is so named because it sends the data in small bursts, or packets.

What is the History of Packet Radio?

Data packet technology was developed in the mid-1960’s and was put into practical application
in the ARPANET which was established in 1969. Initiated in 1970, the ALOHANET, based at the
University of Hawaii, was the first large-scale packet radio project. Amateur packet radio began
in Montreal, Canada in 1978, the first transmission occurring on May 31st. This was followed by
the Vancouver Amateur Digital Communication Group (VADCG) development of a Terminal
Node Controller (TNC) in 1980.
The current TNC standard grew from a discussion in October of 1981 at a meeting of the Tucson
Chapter of the IEEE Computer Society. A week later, six of the attendees gathered and discussed
the feasibility of developing a TNC that would be available to amateurs at a modest cost.

Why Packet Over Other Modes?

Packet has three great advantages over other digital modes: transparency, error correction, and
automatic control.
The operation of a packet station is transparent to the end user; connect to the other station, type
in your message, and it is sent automatically. The terminal Node Controller (TNC) automatically
divides the message into packets, keys the transmitter, and then sends the packets. While
receiving packets, the TNC automatically decodes, checks for errors, and displays the received
messages. Packet radio provides error free communications because of built-in error detection
schemes. If a packet is received, it is checked for errors and will be displayed only if it is correct.
In addition, any packet TNC can be used as a packet relay station, sometimes called a digipeater.
This allows for greater range by stringing several packet stations together.
Users can connect to their friends’ TNCs at any time they wish, to see if they are at home. Some
TNCs even have Personal BBSs (sometimes called mailboxes) so other amateurs can leave
messages for them when they are not at home. Another advantage of packet over other modes is
the ability for many users to be able to use the same frequency channel simultaneously.

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