by Stuart Slade
Updated 04 November 1999
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.
Old P-band = Modern A/B band
Old L-band = Modern C/D-band
Old S-band = Modern E/F band
Old C-band = Modern G/H band
Old X-band = Modern I/J band
Old K-band = Modern K band