There are two quite separate systems for designating radar frequencies. The older one is based on wavelength and was originated during WW2. It goes as follows:
The original wavelength used for search radars was 23cm. This became known as L-band (for Long).
When shorter wavelengths (10cm) were introduced, these became known, quite logically, as the S-band, S standing for Short.
When fire control radars (3cm wavelength) entered service they were designated the X-band radars - because X marks the spot.
It was then hoped that an intermediate wavelength would combine the advantages of both. This was C-band (C = Compromise).
When the Germans decided to introduce short wavelength radars, they selected a frequency of 1.5 cms. This became known as K-band (K = Kurtz, the German word for short).
Unfortunately, the Germans, with unparalleled Teutonic precision, had selected the one radar frequency that is absorbed by water vapor so the K-band radars don't work in rain or fog. Postwar this was countered by selecting frequencies either just over K band (Ka or K-above) or just under it (Ku or K-under).
Finally, the first radars operated with meter-long wavelengths. These were designated P-band (P standing for Previous).
This system was complex, clumsy and difficult to use. Consequently it was replaced by a rationalized system based on frequency with the designations running from the A band to the P band.
- 4 November 1999