Radioröhrenfabrik GmbH

Hamburg's Radioröhrenfabrik GmbH, abbreviated RRF, grew from the radio activities of C.H.F. Müller, also known as Röntgen-Müller, at Hammerbrookstraße 93, Hamburg 15. Between 1914 and 1918 Müller had already made small quantities of receiving and transmitting valves at the Navy's direction. In 1924 its Radio department began making receiving valves in larger quantities and was separated as an independent limited company, Radioröhrenfabrik GmbH. The trade name Valvo was introduced in 1926 and its symbol in 1927: valves retained the RRF stamp until the end of 1926, with Valvo appearing from early 1927. These dates thus describe the commercial introduction and the physical marking change.

In 1927 Philips acquired C.H.F. Müller, including RRF. Between late 1927 and mid-1928 the factory moved to the new Hamburg-Lokstedt site. From 1932 valves were distributed through Deutsche Philips GmbH in Berlin, later named Philips-Valvo-Werke GmbH, also using the Philips-Valvo label. In 1954 Radioröhrenfabrik GmbH, Hamburg became Valvo GmbH, Radioröhrenfabrik Hamburg. After the war, distribution of Philips' extensive component range also moved from Berlin to Hamburg and became Valvo GmbH Hamburg, Hauptniederlassung Burchardstraße. The production range changed over time; semiconductor production is stated to have continued in 2019, which does not establish the current situation.

Hamburg-Lokstedt also made equipment: in 1929 the Valvo RRF1 was built under licence from the Philips Paladin 5, subsequently made in series by Lorenz. Prewar equipment built by RRF bore RRF even when valves from the same factory were already marked Valvo. However, pre-1945 radios bearing Valvo may have come from other Philips factories. A 1940–1944 DKE inscribed Valvo Radioröhren GmbH likewise does not alone prove manufacture in Hamburg. The successful Valvo brand became a common name for the factory, but company, brand and production location must each be placed in their respective period.