Ostar

Ostar was a valve brand of Gustav Ganz & Co. of Vienna, documented at 45–47 Van der Nüllgasse in the city's tenth district. From the mid-1920s the firm made small batches of radio valves, beginning with tungsten-filament types such as the T4 and later producing models derived from existing designs, including the PT43. Products bear the names Ostar, Ostar-Ganz and, less often, Uran or Oxytron: these are commercial marks to be checked on each example, not proof of separate companies. Sales also reached the United Kingdom, where Eugen Forbat offered Ostar valves in London. The Viennese output never approached the scale of major international factories, but it developed recognizable technical solutions.

In the early 1930s engineer Gantner worked on a distinctive family of valves with indirectly heated high-voltage cathodes, intended chiefly for receivers supplied by direct-current mains. Versions for about 110–120, 150 or 220–240 volts could avoid a separate heater transformer. The construction challenge was fitting several metres of extremely thin tungsten wire into a small cathode sleeve: one technical account describes roughly five metres of wire within a tube just three centimetres long and two millimetres wide. Heater power was around 5.5–6.5 watts. The EG50 rectifier was offered with 110- and 220-volt heaters and an output current of up to 50 milliamperes under its specified operating conditions. Other devices included the L1525 output valve and the U920 universal amplifier valve; some examples, such as the A520DG, had a wire-mesh screen around the glass envelope.

The high-voltage range also included rectifier and amplifier variants with designations such as EG100, NG40, NG50, VG45 and W310. Naming was not always uniform: tubes and reference works record different marks and heater voltages, so two EG50 examples should not be treated as identical without checking their inscriptions. A patent application filed in 1931 documents Ganz's interest in the heated cathode. A later historical account attributes the purchase of patents for this solution to Philips, but the precise extent of any transfer and its connection with the Philips U and V series require firmer documentary verification. Ostar's story remains that of a small Viennese brand that tried to solve a practical problem for mains-powered receivers, leaving tubes with unusual forms and electrical specifications.