At the start of WW2 UK did not have a really good wireless receiver suitable for intercept work, but in the USA there were 80,000 radio amateurs and many more short wave listeners for which manufacturers had provided some excellent receivers.
The needs of radio interception were closely allied to those of the radio hams and many of these radios were purchased from the USA by UK. Government. The National HRO receiver shown on the right was found to meet the requirements and many were obtained for use at the “Y” stations. Operators would stick cardboard circles around the tuning knob marked in pencil with important frequency settings.
The Hallicrafters SX-28 "Super Skyrider" was another receiver that appeared in the early 1940s in the USA with military use in mind. This receiver was also used in the UK Y stations.
By the latter part of WW2 a good intercept receiver had been designed and constructed by the British military.
The R206, shown on the right embodied most of the valuable characteristics of the best US receivers and was used widely in the Y stations.
A number of other receivers were also used but the National HRO was always the clear favourite amongst the wireless operators who had to use them to search for weak signals for long hours often in uncomfortable conditions.
The intercepted messages were always in morse code and operators needed to be competant at quite high speeds. The smallest error would cause great difficulties to the codebreakers at Bletchley Park so the receivers needed to be very effective and very reliable. The receivers they used needed to offer accurate frequency, good selectivity and speed of operation when frequencies needed to be changed at a moments notice. Regular checks and calibrations of the receivers were carried out frequently.