Rotary joints

Updated June 14, 2008

New for June 2008! Rotary joints are what is used to connect a radar's transmitter and/or receiver to its antenna, in the case of an antenna that must rotate (like an airport surveillance radar). There are tons of other examples of rotary joints that are not microwave, in the electronics industry as well as hydraulics.

"Rotary joint" is sometimes referred to as "rojo", this is an example of portmanteau in engineering.

Rotary joints are usually waveguide for high-power applications (but air coax is also possible). Here's an image of an waveguide rojo we found recently on Ebay. The seller mentioned that the "waveguide part" measures 0.5" x 1.2" inches which isn't a standard size so he must have measured it inaccurately. It must be intended for either C-band or X-band.

Here's one for Ka-band (WR28 rectangular waveguide)

There's only a small list of manufacturers of rotary joints in the world, maybe one of them might want to sponsor this page and tell us all about the topic!