“Breaker Breaker”, this is the C64 calling

In the early 90s, sending files and data from one computer to another over a telephone line was something that was becoming more and more in vogue thanks to the internet, BBS systems etc.
The only drawback was the communication cost as in most countries, telephone calls were still quite expensive.

How nice it would have been if you were able to transmit data over long distances, without the cost of the long-distance call… utopia surely, or maybe not…?

A popular free for all communications method already existed and was well know with amateur radio services, called the “CB” or “Citizen Band”.  Most of us know this as the way truck drivers communicate with other drivers on their long drives through the country (like Kurt Russell in “Big Trouble in Little China) or from the taxi cab driver who gets his info from the dispatch.
It wouldn’t be too long or some clever genius would find a way to transmit data through the ether on the CB-channels and it just happened that the Commodore 64 was a fantastic device to make this happen.

We know the classic tape drive from the C64 uses the “sound of data” stored on a datasette tape to load and save information.  Copying programs was merely a case of putting in the original and an empty tape in a double-deck tape rack on your HiFi set and pressing “Record”.  The empty tape would copy the noise from the original and hence copy the data stored in it.

Transmitting the “sound of data” via CB would allow a receiver to store the data in a similar fashion, but the data would come not from a tape, but from the ether.  That would be the theory, but of course, it would not be as easy as this, as there needed to be a mechanism to tell the receiver which information it was receiving (i.e. what is the start and end of the information and so on).  The trick would be to use “Packet Radio”, a technique already used in the data communications of the telephone employing the AX.25 standard with a transmission speed of 1200 Baud.
All this, came packaged for the C64 in a special modem that you could connect to the datasette port.  The modem would then be hooked up with a special cable to the CB transmitter/receiver’s microphone.  Special terminal software, such as “Digicom” completed the setup and allowed you to load text and files and start transmitting them, as well as save received files to disk.

You could also “scan” the airwaves and “plug” into an already existing datastream.  Pretty cool!

So, what was the distance you could cover with this?  Typically, the CB had a range of 5 to 20 kilometers (depending on the size of the antenna) and up to this distance, the signal still had good quality, but there was a phenomena called “Shooting Skip”, which allowed communications over more than a 1000 miles (although I never heared of this being used to transmit data).
The physics behind it, are that all frequencies in the HF spectrum (3–30 MHz) can be refracted by charged ions in the ionosphere.
The ability of the ionosphere to bounce signals back to earth is caused by radiation from the sun.  The amount of ionization possible is related to the 11-year sunspot cycle. In times of high sunspot activity, the band can remain open to much of the world for long periods of time.  During low sunspot activity, it might not be possible to shoot skip at all except during periods of sporadic electron propagation, which occur from late spring through mid-summer.

So, how much would this equipment set you back?  Not too much really as the Packet Radio modem and cable usually cost around 80 Euro.
For the CB and antenna, you had a selection of models and types in different prizes.

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One Response to “Breaker Breaker”, this is the C64 calling

  1. Stephen Walters G7VFY

    Hi there,

    I am a radio ham that likes tinkering with old computers.

    I have commodore 64, VIC-20 and Amigas.

    I am interesting in RTTY, packet radio PSK31, FT-8, JT-65 etc etc


    Stephen Walters G7VFY

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