My first job was as an apprentice at a Post Office HF radio station, Bearley near Stratford-upon-Avon. It was part of the HF point-to-point system that provided worldwide telecommunications. It was state of the art in 1967 and scrapped in 1980.
The station had 50 of the first professional, transistorised communications receivers, Plessey PVR800s. The early versions had some germanium transistors which proved to be unreliable. They were replaced by the ultra modern silicon types!
They were used for telephony, 4 voice channels on double side band reduced carrier. The audio was inverted so that short wave listeners could not eaves drop.
There were also 50 Marconi HR11, valve telegraphy receivers. Each had the capability running 48 telex services on one radio channel using time division multiplex.
As services were transferred to satellites the station took over the maintenance of UK coast stations used for marine communications. They also suffered the same fate. Eventually all HF communications was taken over by satellites and the point-to-point and coast station were closed down. This Post Office film from 1979 shows something of what HF coastal communications in the “good old days”.
It was then end of an era and still saddens me to think that all the old skills have been lost, particularly commercial Morse.
If you want to read more about the HF point-to-point HF radio network, then see this book by Paul Hawkins who worked at the Dorchester TX station. (click the image >)
Remember, radio amateurs still use Morse!
Also see the Radio Officers Association