Wave guide is special hollow conduit used to pipe an electromagnetic signal to a dish antenna with as little distortion as possible and distortion from reflected waves bouncing off an improperly assembled or inadequately tuned waveguide will impede the signal. Attenuation is also an issue should moisture get inside the wave guide. For this reason, wave guide is pressurized with air from an air-conditioned room to prevent too much moisture from entering the waveguide.
Wave guide comes in a variety of shapes and designs but fall into two basic categories: rigid and flexible. The type of waveguide chosen depends upon the application's frequency and power level. Again, as with all discussions of electromagnetic energy, it is hard to describe the behavior of the energy without resorting to mathmatics.
RIGID WAVEGUIDE
The wave guide is not randomly shaped. The signal must reach the antenna with as little distortion as possible despite the corners the signal must bounce around to get from the amplifiers to the dish in phase with the load. The waveguide can be bent in the Easy or Hard direction to produce E-bends or H-bends.
H-BEND
H-bends bend the magnetic part of the electromagnetic signal being conducted down the waveguide.
E-BEND
E-bends bend the electric part of the electromagnetic signal being conducted down the waveguide. The radius of a gradual E-bend must be twice the wavelength of the frequency carried by the waveguide in order to avoid reflecting energy.
FLEXIBLE WAVEGUIDE
HELIAX
Heliax is circular ridged tubing also designed to carry a transmitted signal to the dish after amplification. Like the rigid wave guide, the tubing is filled with air, so the maximum power reaches the feed horn at the dish.
COAXIAL CABLE
Coaxial cable is a copper wire, surrounded by cladding and a woven mesh jacket. Coaxial cable is most often used to carry Intermediate Frequency or L-band freqencies within the earthstation.