UHF relay equipment

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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.

Where other radiation patterns were required, the trough antenna was used for transmit, as at Hemel Hempstead, Ventnor and some sites in Wales.

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....

Later developments - logs with everything?