In the US and the UK there is a new amateur radio band that has been allocated, the first new band in something like 30 years (I think). It operates on frequencies around 5000 kilohertz (your AM radio recieves frequencies from 530 to 1700 kilohertz).
There are a few unique things about this frequency allocation:
1. Every other amateur band has been allocated a frequency range for use (such as 3500 kilohertz to 4000 kilohertz). This band (called the 60 meter band) is allocated for channelized use only, like a CB. There are no other amateur frequency bands like this, and it was a point of contention for some of the grouchier old hams. There are 5 channels on the band (in kilohertz or kHz): 5330.5, 5346.5, 5366.5, 5371.5, 5403.5.
2. The power output is limited to 50 watts. On most other amateur bands in the US, the legal limit is 1500 watts.
3. Communications must be made in a mode called upper sideband. As you might have guessed there is a mode called lower sideband as well. By convention, operation below 10000 kHz when using sideband is done with lower sideband. The reason for bucking the trend in this case is probably to give us hams a way to communicate with the government (as the original author said).
4. It was originaly stated that hams would have secondary access to the band (on most bands we are the primary or the only user), and that the purpose of the band was for effiecient interstate communication in the event of an emergency. I didn't really put 2 and 2 together regarding this band until I read this story.
Anyway, hope this helps. Let me know if you need further clarification. :)
Although it bucks the tradition of using LSB, the use of USB allows a simple AM receiver with a BFO (beat frequency oscillator) to detect and recover usable audio. LSB appears "inverted" to an ordinary AM receiver. I suspect there is a population of "legacy" receivers that the policy is intended to "include".
A short technical comment follows for others on the thread that might be interested in how and why the signals are constructed in a particular fashion.
USB and LSB are forms of "single-sideband, suppressed carrier". The carrier and modulating audio are mixed on a balanced bridge. The output is "double-sideband, suppressed carrier". Ordinary AM is "double-sideband, full carrier". A narrow filter tuned above the carrier frequency permits USB to pass and excludes the LSB signal. A similar filter tuned below the carrier frequency would pass LSB and exclude the USB signal. Since only the sideband carries useful information, it is advantageous to strip out the carrier and the redundant side-band.
Found this interesting tidbit in a spy numbers newsletter
What does "spy numbers" newsletter mean?
With you being a ham radio person, what is your take on the UK info (credibility, etc.)?