UHF relay equipment
This will be a summary of the evolution of UHF TV relay equipment - from troughs and cylinders to logs and panels. It is likely to be quite a long time before it is finished!
The first UHF relays
Naturally the first relays followed the first main stations - and were intended to serve significant populations. Crystal Palace provides a number of early examples, some of which are little changed despite the passage of time and DSO.
Hertford is a good example of an installation using the standard equipment of the time, but on an existing structure. As documented in the BBC Research paper the transmit antenna is a stack of 16 dipoles, giving a cardioid radiation pattern, and there are twin troughs for receive (main and standby). This arrangement was used at most of the early relay sites although in a number of cases the troughs were replaced by log periodic antennas (singly or in groups) in later years.
Other early-era relays of Crystal Palace include Guildford and Reigate. Although both sites still feature a cylinder for transmit, the troughs were replaced by logs at some point in the past. Both are line-fed following DSO, and Reigate's cylinder is now a non-standard type, see DSO section.
Reliability was apparently a major concern in the early days, hence the twin troughs and division of the 16-dipole stack into two halves which were fed independently [Hertford paper?]. At some stage a decision seems to have been made to use a single trough, except in "difficult" locations.
By the time the Woolwichrelay was built, a panel antenna had been developed for use on transmit. These were used in a variety of combinations and even featured at some main stations, notably Black Hill. [needs ref to R&D article on panels]
With a few exceptions, early relays tended to use structures of standard design....