File:Four tube 500W transmitter 1922.jpg
Original file (1,518 × 1,168 pixels, file size: 249 KB, MIME type: image/jpeg)
Captions
Captions
Summary[edit]
| Description |
English: A 500 watt amateur vacuum tube AM and CW radio transmitter built around 1921 by Frederick Koenig, 2BAK, of Tarrytown, New York. This is an early tube transmitter; "hard" vacuum tubes suitable for transmitting only became available to amateurs in 1919 after World War 1. The transmitter uses a Heising-Colpitts oscillator circuit with the 4 tubes in parallel for CW (telegraphy) operation. For AM telephony two of the tubes are used as modulators. With 600V on the plates the transmitter produced about 1 A antenna current.
The four triode tubes on the front panel are mounted upside down; this common early practice was to prevent the fragile hairpin-shaped filaments from sagging when they got hot and touching the grid. Under the tubes, the dial on left is the feedback capacitor, on the right is the grid capacitor, both 1.5 pF. The multiposition switches up the center are the feedback, plate and antenna taps on the tank coil. The 3 meters in the center are (l-r) plate current of the two oscillator tubes, filament voltage, and plate current of the two modulator tubes. The 6 single-throw knife switches at bottom are for: CW, ICW, AM (phone), test buzzer, filament current, and plate DC. A relay attached to a push-to-talk switch on the microphone turned on the plate voltage. The filaments are kept heated with a 1 ohm resistor in the filament lead when not transmitting. |
| Date | |
| Source | Retrieved January 25, 2014 from Frederick Koenig, "Four-tube CW Transmitter at 2 BAK" in Radio magazine, Pacific Radio Publishing Co., San Francisco, Vol. 4, No.1, January 1922, p. 16 on Google Books |
| Author | Frederick Koenig |
Licensing[edit]
 |
This media file is in the public domain in the United States. This applies to U.S. works where the copyright has expired, often because its first publication occurred prior to January 1, 1929, and if not then due to lack of notice or renewal. See this page for further explanation.
|
 |
 |
This image might not be in the public domain outside of the United States; this especially applies in the countries and areas that do not apply the rule of the shorter term for US works, such as Canada, Mainland China (not Hong Kong or Macao), Germany, Mexico, and Switzerland. The creator and year of publication are essential information and must be provided. See Wikipedia:Public domain and Wikipedia:Copyrights for more details.
|
File history
Click on a date/time to view the file as it appeared at that time.
| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 04:34, 3 March 2014 | | 1,518 × 1,168 (249 KB) | Chetvorno (talk | contribs) | User created page with UploadWizard |
You cannot overwrite this file.
File usage on Commons
There are no pages that use this file.
