Television & Radio Hardware - Aerial Types
Contract aerials are the bottom of the pile in terms of quality. They can be identified by a large, flat reflector on the rear of the aerial. Being low quality also means they are cheap, so are relatively common.
In most cases, contract aerials work well enough though they don’t offer the best option for a new install.
Another point to be aware of is that the relatively large reflector can cause a high wind load. This is of particular note for chimney installations.
Yagi aerials and relatively common and feature a large reflector at the rear of the aerial which focuses the signal down onto the directors which in turn focus onto the dipole. This method causes Yagi antennae to be very directional and need to be accurately aimed at the transmitter.
For areas which have a poor signal, a Yagi will almost certainly be the best choice. Particular notice should be taken as to which aerial grouping you are buying and which you require.
Due to the large size of the reflector, the number of elements and the overall length, Yagi aerials have a high wind loading. The length of the aerial means a mounting cradle should be used, as end-mounting can cause a high twisting force in strong winds. In fact, some Yagi aerials are over two metres long!
Log Periodic aerials are a more recent invention and are relatively rare. They are the type of aerial that most people should install when in medium and good signal strength areas.
The negatives of Log Periodics are that they are slightly more expensive and some care also needs to be taken in tilting the front of the aerial up a few degrees when installing, as water can corrode the connection point of the cable (which is located at the front of the aerial rather than the rear).