27MC CB Cell Phone from 1977 was the same size as a mobile phone

huh? The mobile phone only became popular and compact in the 1990s, didn’t it? The small device you see here was therefore not a mobile phone, although you could use it to make ‘calls’ via 27MC.

CB, Citizen’s Band and 27 MC

Almost the entire radio spectrum had been given away by the government. The entire radio spectrum? No, one single band, the 27 megahertz, in English 27MC, was and still is released. In the US, this bandwidth is known as CB, Citizen’s Band. in the Netherlands this band is between 26.965 MHz and 27.405 MHz, which corresponds to a radio wavelength of 11 m.

Once very popular were the 27MC transmitters, with which you can use this free radio frequency, such as the device above. Even today they are still used by amateurs, some truck drivers and agricultural contractors. This enabled you as a trucker or, for example, as a lumberjack or worker on an oil pipeline, to communicate with others, miles away. Without the need for a radio license.

40 channels, 25 km range in a straight line

There are 40 frequencies within the 27 MC band in the Netherlands. These are called channels in the 27 MC world. There are also so-called export versions, with which you can reach more than 200-300 channels, and the power is often up to 10 times higher than the 4 W permitted in the Netherlands. These often also consume channels outside the permitted range, which is why they are forbidden to use in the Netherlands.

The range of the version permitted in the Netherlands is around 25 km. This has to do with the curvature of the earth, because at greater distances there is no longer a direct line of sight.

The ionosphere is a layer in the atmosphere that contains many charged particles. This works like a mirror for radio waves. If the ionosphere is extra active, for example due to a solar eruption, the range can be many thousands of kilometers. The radio waves then bounce back and forth between the ionosphere and the Earth’s surface.

Advantages and disadvantages of 27 MC

And a data bundle, call bundle or subscription? No. That was not done via transmission towers, but directly. So the use is free. The 27MC transceivers were, just like a mobile phone, radio transmitters and receivers at the same time. This predecessor of the mobile phone was especially popular in the 1980s.

Of course they also had disadvantages, which is why they have been replaced by mobile phones. So there is the limited range. Eavesdropping was easy, because devices often shared the same frequency.

You had to hit the send button every time you wanted to say something. And of course, whoever you call must have their device on. Today’s mobile phones do not have these disadvantages.

Handy for preppers

Chances are small that 27MC will become popular again. Cell phones are too good and too handy for that. Still, it’s a good idea to have one of these transmitters at home if you live in a remote area. Because what if for whatever reason, for example a natural disaster, the GSM transmission towers are down? Then these 27MC radio transmitters are the only way you can communicate with the outside world.