View source for WD-11

The '''WD-11''' [[vacuum tube]], a [[triode]], was introduced by the [[Westinghouse Electric]] corporation in 1922 for their Aeriola RF model radio and found use in other contemporary [[regenerative receiver]]s (used as a detector-amplifier) including the Regenoflex and Radiola series.
The WD11 and "RCA-11"<ref>{{cite book|title=RCA Receiving Tube Manual RC-13|year=1937|page=98}}</ref> (and later simply named "11" by RCA<ref>{{cite book|title=RCA Receiving Tube Manual RC-14|year=1940|page=157}}</ref> and Philips/Miniwatt<ref>{{cite book|title="Miniwatt" Technical Data|year=1958|publisher=The "Miniwatt" Electronics Division of Philips Electrical Industries Pty. Limited, N.S.W.|location=Australia|edition=6th|page=56}}</ref>) have the following characteristics:
{| class="wikitable"
|-
! Socket:
| colspan="2" | [[Tube socket#Early bases|UV4]] ''(also known as WD-4-Pin)''
|-
! EIA/RETMA Base Diagram:
| colspan="2" | '''4F'''
|-
! Description:
| colspan="2" | Detector Amplifier Triode
|-
! Filament:
|| Directly heated 1.1 [[Volts|V]] || 0.25 [[Ampere|A]]
|-
! Plate (anode) Voltage:
|| 90V || 135V ''maximum''
|-
!Grid Voltage:
|| -4.5V || -10.5V
|-
! Plate Current
|| 2.5 mA || 3.0 mA
|-
!Plate Resistance:
|| 15.5 kilohms || 15 kilohms
|-
!Amplification Factor (mu):
|| 6.6 || 6.6
|-
!Transconductance (g<sub>m</sub> or S):
|| 0.425 mA/V || 0.44 mA/V
|-
! Power Output: (P<sub>o</sub>):
|| 0.007 W || 0.04 W<ref>{{cite web|title=WD 11|url=http://oldradio.qrz.ru/tubes/foreign/03/WD11.gif|accessdate=7 January 2013}}</ref>
|-
! Grid-plate Capacitance (Cga):
| colspan="2" | 3.3 pF
|}
<references />
==Drawbacks==
[[File:WD-12 Receiving Tube, Westinghouse, c. 1923 - National Electronics Museum - DSC00121.JPG|thumb|Westinghouse WD-12]]
[[File:UX199 Receiving Tube, RCA - General Electric, c. 1922 - National Electronics Museum - DSC00117.JPG|thumb|RCA UX-199]]
The WD-11's design was somewhat ill thought out, when the filament burns out it has a tendency to contact the plate, feeding high voltages back through the heater circuitry and subsequently burning out the filaments on the remaining tubes,.
The WD-11 also has a unique 4 pin base layout that was unlike any subsequent UV and UX style tube base. It had 3 "small" pins and one "large" pin. (Later UV based tubes relied on an index pin on the side of the tube base and UX tubes had 2 large and 2 small pins to ensure proper indexing.)
It was replaced just a year later by higher performance tubes which were less likely to encounter the filament shorting problem, Westinghouse Electric's WD-12 and [[General Electric]]'s UX-199. No radios using the WD-11 tube were designed after 1924, RCA ceased production and issued a service bulletin describing how to retrofit existing sets to use the newer UX-199 triodes.
==Collectibility==
Because of its rarity it has become one of the most valuable vacuum tubes in the world. New-old-stock units have sold for as much as US$180 and used tubes for over $100, more than the original price of the radios that use them. Collectors rarely, if ever use these tubes for fear of burning them out.{{fact|date=November 2022}}
==Substitution==
Sets that use the costly WD-11 and UV-199 tubes can be modified to use the 1A5/GT octal power [[pentode]] (Which cost around $2.50) by wiring a 5.1 [[ohm]] [[resistor]] between the pins of the filament and fabricating an octal-to-four pin adaptor. The pin for the 1A5's suppressor is left unconnected and the screen connected to the plate.
The type 12 (also known as RCA-12) is electrically identical to the type 11, but with a more common [[Tube socket#Early bases|UX4]] base.
==External links==
*[http://www.tubecollectors.org/archives/wd11.pdf Data sheet for WD-11]
Here is a link on how to modify other tubes to use in place of a wd11:
* https://www.6v6.co.uk/vcomp/tech_tips/wd11.htm
[[Category:Vacuum tubes]]