E-mail:[email protected] or Packet: [email protected]
Computers have very quickly found its place in our hobby - amateur radio. Computers can help us with learning CW, editing contest logs, working on RTTY, calculating satellite positions, etc...
But what if we want to be connected from our computer to another computer, which is storing some interesting data, which we want to read?
Firstly we have to think, how can we make the connection between two computers. Then we have to determine adequate communication channel -because we are HAMs, we have chosen a radio channel to be our communication channel. So communication will take a place via HAM radio transceiver. But we now face another problem - digital signals from our computer can not be directly transmitted through our transceiver, so we need another piece of equipment called MODEM, which will transform computer signals in to signals which can be transmitted by our transceiver. Name MODEM is coming from words MOdulator-DEModulator. This piece of equipment is modulating computer signals that they can be transmitted and it is also demodulating reception signals from transceiver in to computer signals. With different modems we choose different modulations and different speeds of data transfer.
For succesfull transfer we must also define communication protocol, which is defining ways of connection, data transfer and disconnection. Radio-amateur communication protocoll is called AX25 (AX25 Amateur Packet-Radio Link Layer Protocol) and it is also defining that data is being transfered in small groups called packets, and because of this, radio amateurs have chosen name PACKET RADIO.
Simply spoken, packet radio is in fact a mean to transfer data (text, images, computer programs, ...) with wireless transmitions between radio amateurs. AX25 -Packet Radio protocol is an amateur adaptation of world famous X25 protocol and it is insuring error free transmissions, because errors are detected and corrected by asking another transmission from the sender. With this protocol multiple users can share the same channel.
2. USING AN AMIGA FOR PACKET RADIO
If you will be using an Amiga computer with a TNC or a multimode controller then even an old Amiga 500 with 512 kB of memory and with single disk drive should be enough. If you are going to use your Amiga with BayCom modem then I recommend you at least 14 MHz 68000 CPU as BayCom modem will take a lot of CPU time and can cause system crashes on Amigas with a 7 MHz 68000 CPU. Recommended equipment is an Amiga 1200 with at least 1 MB of FAST RAM and a hard drive (with this equipment you will be able to multitask without any problems).
WHAT ADDITONAL EQUIPMENT DO I NEED TO USE
AN AMIGA FOR PACKET?
You need something of the following:
A.) a TNC or a multimode controler
TNC stands for a Terminal Node Controler and this is in fact a micro computer with its own CPU, RAM and special software which is normaly stored in an EPROM chip and controls modem operations. Usually you get a TNC with already built in modem. A multimode controller usually supports several aditional amateur radio digital modes beside packet radio (AMTOR, PACTOR,...). TNC takes some burden from the Amiga's CPU as it is making some or all calculations needed around packet radio protocol. TNCs can also be used for storing messages (PMS - Personal Message System) when your Amiga is turned off.
With an Amiga you can 100% use one of the next TNCs:
Please check what sort of software is stored into your TNC's EPROM before choosing adequate programs or different modem drivers for packet radio programs.
BayCom modem is a very simple and also very dumb modem which finds its place on the serial port. All data and protocol calculations for packet radio are done by computer itself and that is why an Amiga with 7 MHz 68000 CPU is usually too slow.
2.1.1 What should I choose of the above?
If your local packet radio network supports higher packet radio speed for user access and if you are intrested in downloading large ammounts of text and binary files then I recommend you a TNC with with a high speed modem, because you will not regret it in the future. If your local packet radio network supports only 1200 bps user access or if you are intrested in reading only text messages and downloading shorter binary files than even small and cheap BayCom modem would be enough. If your Amiga is too slow for BayCom modem than try to get a TNC with a built in 1200 bps modem. (bps stands for bits per second)
I am personally using my Amiga 1200 with a home made TNC-2 in KISS mode, built-in Manchester modem for high speed packet radio - 38400 bps. I use a home made WBFM (Wide Band Frequency Modulation) 435 MHz transceiver which was especially contructed to handle high speed packet radio transmissions (up to 76800 bps) and cannot be used for ordinary voice operation
If you are interested in the construction of this RTX or in Slovenian high speed packet radio network than check the info on S5 Radioamateurs Internet home page www.hamradio.si or www.ljudmila.org/hamradio"
There are several terminal, BBS and other packet radio programs available for Amiga computers. There can also be obtained some Amiga programs which can be used for TCP/IP transmissions via packet radio. Most of the common packet radio users use only a packet radio terminal program which enables them to be connected to a local digipeater, BBS or a user and to exchange (upload/download) text or binary data and to make simple chats via keyboard with his/her friends.
The most used packet radio terminals for Amiga computers are AmiCom and Amipac. I have found AmiCom (written by Gerhard Loder - DL3MGQ) to be one of the best packet radio terminal programs available not only for Amiga but also for PC computers, because it is very simple to use (very good for beginners), it supports even up to 256 channels for 256 simultaneous connects (if you have enough RAM and if your TNC supports this) - but you propably won't need more than 10, it supports AUTOBIN protocol for downloading/uploading binary files (like SP on PCs), it handles downloading of 7Plus encoded files automatically, it supports Amiga's multitasking capabilities, it has very nice graphic environment (icons for some functions (AmiCom version 2.3 and higher)), supports BayCom modem and HOST mode or KISS (also SMACK and CRC-KISS Flexnet) TNCs, and many more interesting and usefull features and the only thing I miss is lack of support for Yapp protocol which is very usefull for uploading/ downloading larger binary files, but this is the feature which is being supported by Amipac software.
Beside packet radio terminal, you would very propably need a 7Plus file encoder/decoder. 7Plus is a special software which is enabling you to send or receive a binary file as several text files/bulletins on packet radio BBS system, it in fact encodes binary data into 7 bit code which can be freely transfered (forwarded) between several BBSs without data loss. But if data loss or data corruption occures it informs you of that and ensures that only corrupted/lost parts of data (7Plus) files are resent and not the whole set of 7Plus files. The latest version of 7Plus for Amiga is 2.18 (from June 97) and was written by DG9BJA.
Packet Radio software is available for download from the Aminet or from the AARUG PD Library