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ID = 15013
United States of America (USA)
Brand: Common type USA tube/semicond.
Tube type:  HEPTODE   UHF 
Identical to VT-128 = 1630 = CV2715
First year 1939 -- Collector info (Sammler)

Base SPECIAL TUBEBASE in general (Codex=Eo)
Description The VT-128 / 1630 is an orbital-beam hexode electron-multiplier VHF amplifier (secondary emission). The valve measures 55x50mm overall (25mm across the body). The VT-128 orbital-beam hexode was used in early SCR-270 radar sets at 106 MHz (also used in Pearl Harbor) as an electron multiplier preamplifier. Due to noise and reliability issues and short working life of about 50 hours only, it was eventually replaced by a module using 6J4 triodes. The VT-128 or 1630 was also used in Grote Reber's pre-war radio telescopes at 480 MHz, with a 4 stage amplifier providing 100 db of gain. How it works: Electrons come off the heater, pass through the grids, and are accelerated in two curves around a round beam forming electrode. They whack into one anode, which has a special coating which emits several electrons for each one which hits it. These "new" electrons are received by the second anode. Wikipedia: "In the 1930s special amplifying tubes were developed which deliberately "folded" the electron beam, by having it strike a dynode to be reflected into the anode. This had the effect of increasing the plate-grid distance for a given tube size, increasing the transconductance of the tube and reducing its noise figure. A typical such "orbital beam hexode" was the RCA 1630, introduced in 1939. Because the heavy electron current in such tubes damaged the dynode surface rapidly, their lifetime tended to be very short compared to conventional tubes." 
Text in other languages (may differ)
Dimensions (WHD)
incl. pins / tip
55 x x mm / 2.17 x x inch
Information source Taschenbuch zum Röhren-Codex 1948/49   
VT-128: USA
John Albion

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