Catalogue
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Marconi Radio Valve Type MH4, by Marconi Company, London, 1930s
Inventory Number: 24996
Number of documents: 3
Document Type: Miscellaneous Note
Document Heading: Historical Background - British Radio Valve Manufacturers' Association (BVA)
Text:
The British Radio Valve Manufacturers' Association (BVA) was established in July 1926 and was a registered trade union. It had been preceded by the Valve Manufacturers' Association, which had established a 'Memorandum of Sales Plan'. This agreement, which was signed by the seven major British valve manufacturers, secured a uniform practice in the sale of radio valves for broadcasting purposes in the UK. Practical examples included similar discounts and sales conditions, and were considered a form of restrictive practice. This association continued into the 1950s.
Document Type: Miscellaneous Note
Document Heading: Technical Details
Text:
The MH4 indirectly heated amplifier triode is of unusual internal construction. The cathode assembly passes through the far end of an oval grid. The grid is fixed only at the outer end to a stout single rod. The anode is a thin sheet and is open at the front of the grid support. The channel formed by the anode sheet encloses the cathode and the far end of the grid. This method was known as Shortpath Construction. The MH4 is identical in construction to the landmark Mazda Type AC/HL long-life valve which was introduced in the 1930s and continued in use until the 1960s.
Document Type: Miscellaneous Note
Document Heading: Manufacturer Details
Text:
Marconi-Osram Valve Co. Ltd. was founded in 1919, and took over the manufacture of Marconi valves from Ediswan, the trade name of the Edison and Swan United Electric Light Company Limited. The M-OV, as it was later known, was a joint Marconi-GEC valve-manufacturing company. It produced all of its valves at the Osram Lamp Works at Hammersmith, London.
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