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R Type

Sensibly equivalent to:
R. TM
See also:
The Dawn of Broadcasting in the UK - In the Beginning - Osram
    
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The R Type is the classic hard vacuum receiving valve from 1916. We have an example of the clear spherical envelope version of this valve (R Type) in addition to this balloon shaped version and several others. The insert shows the electrode construction, which is similar to the spherical version but has quite different support structures. The grid can be seen in the picture and consists of a bright wire helix that is held firm on the long axis. The anode is a bright metal cylinder rigidly held at both ends.
This exhibit is a later version made by M-OV around 1927. Some M-OV R Types were gettered around this period. Note that the large BBC roundel was not used after the end of October 1924 and the small BBC roundel which followed it was used until 1927 when it was replaced by the oval BVA logo. Around 1928 the style of base pins was altered to the modern sprung type. The M-OV type R was still listed as available at the outbreak of WWII.
However, this exhibit could equally well be an M-OV Type DER of the same period as dull emitter thoriated tungsten wire filaments would look the same as tungsten bright emitter filaments.
The balloon envelope is 44 mm in diameter and, excluding the B4 base pins, is 80 mm.
References: 1003. Type R Type was first introduced in 1916.

 

Updated January 08, 2013.
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