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Photos by John Rhodes Page last updated: 2024-04-23


Bromsgrove and its sister site Malvern were originally planned to be 10 kW ERP sites but were downgraded to 2 kW ERP. Whatever the timing of this change, the IBA installed 1 kW transposers which were then underrun. They were subsequently replaced by Pye 200 watt transposers and the 1 kW equipments retuned to be used elsewhere - Bromsgrove went to Arfon and Malvern to Rosneath, which itself had been downgraded from a
50 kW ERP main station to a 10 kW ERP relay.

The 1 kW transposer made by LGT in France was the mainstay of the ITA/IBA 10 kW ERP relay stations. However, this class of station opened later than planned owing to the cancellation of the 4 x 250 watt traveling-wave tube (TWT) Plessey system originally intended for them. This was because the Plessey equipment could not meet the intermodulation product (IP) specification owing to the excessive amount of non-linearity pre-correction required by the TWTs. Somewhat hurriedly, alternative equipment had to be sourced, the first of which was installed at the bottom of the water tower at Reigate.

A rather threadbare Bromsgrove tower in 1975 supporting only two trough receiving aerials and the UHF transmitting aerial.

Bromsgrove building 1975

Pye 200 watt transposers 1975

The LGT 1 kW transposer, shown here undergoing retuning at Bromsgrove without its meter panels, consisted of two 500 watt amplifiers using Thompson CSF TH331 tetrodes each driven by a 50 watt stage using a TH326 triode. The centre rack contained receivers, 1 watt output upconverters (in a drawer known as the 1 watt drawer) and the 50 watt amplifiers.

However, the LGT 1 kW was not maintenance-free, particularly at high channels where the gain of the 500 watt stage was only 10dB requiring about 1.25 watts from the 1 watt drawer. It was less of a problem with the 13dB gain at low channels. A substantial modification programme was carried out in 1977 to replace all the upconverters with low level mixers and linear amplifiers.

Bromsgrove index

Arfon | Malvern | Reigate | Rosneath

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