CB 934MHz:
When CB radio became legal in Britain on 2 November 1981, the government introduced two separate services:
- 27 MHz CB: 40 FM channels, maximum 4 watts transmitter output.
- 934 MHz CB: 20 FM channels, maximum 8 watts transmitter output.
The 934 MHz service was interesting because it offered a completely different kind of CB operating experience. It attracted dedicated enthusiasts who were interested in UHF radio, aerial experimentation and long-distance line-of-sight communication.
Technical specifications:
| Feature | British 934 MHz CB |
|---|---|
| Introduction | 2 November 1981 |
| Frequency range | 934.0125–934.9625 MHz (revised allocation) |
| Channels | 20 |
| Channel spacing | 50 kHz |
| Modulation | FM |
| Maximum transmitter power | 8 watts |
| Maximum ERP | 25 watts (base/mobile) |
| Wavelength | Approximately 32 cm |
| Final legal operating day | 31 December 1998 |
The frequencies were originally 934.025–934.975 MHz, but were shifted down by 12.5 kHz in 1983.
Why was 934 MHz so interesting?
Unlike conventional 27 MHz CB, which can produce extremely long-distance contacts through ionospheric propagation, 934 MHz signals normally travel by line of sight. This meant that aerial height, location and terrain were especially important.
From a good hilltop or with suitable directional aerials, operators could achieve impressive distances. Between well-sited fixed stations, communications over many tens of miles were possible.
Other advantages included:
- Shorter, more manageable aerials.
- Less of the electrical interference commonly experienced on 27 MHz.
- Directional beam aerials that could provide useful gain.
- Generally more disciplined operation, partly because the equipment was expensive and the community was small.
However, buildings, hills and other obstructions could significantly reduce the range, making mobile-to-mobile communications unpredictable.
Why did the government close the band?
The decline of 934 MHz CB wasn't simply due to lack of popularity.
In March 1988, the government announced plans to replace the existing allocation with a proposed European short-range radio service operating around 933–935 MHz.
The consequences were significant:
| Date | Event |
|---|---|
| 1981 | 934 MHz CB legalised |
| 1984 | 934 MHz Club UK established |
| 1988 | Government announced withdrawal of the equipment specification |
| 30 December 1988 | New manufacture and importation prohibited |
| 1996 | Proposed replacement digital short-range service abandoned |
| 31 December 1998 | Last day of legal 934 MHz CB operation |
Ironically, the proposed replacement system never became commercially successful. The growth of mobile telephones had largely overtaken the original plans.
PMR 446 Radio:
Some people are now using PMR 446 radios for local contacts. The advantages over 27 MHz are small aerials and no interference. With a decent antenna, good distances can be achieved. Although I don’t think that’s strictly legal!