No.49
Amateur Radio
EL509
Evaluating the Svetlana EL509/6KG6 Tube
By: Bob Henry
Article as first appeared in Electric Radio Magazine - March 1999
Sweep tubes have been used quite extensively in linear amplifiers and RF ouputs for many amateur radio transmitters. While these tubes yield a plentiful quantity of output power, they have not been considered to be as durable as other tubes for RF, such as the 6146. However, SVETLANA has produced a high performance 6KG6/EL509 that lends itself well in the applications of sweep tube RF output. The SVETLANA 6KG6 has an increased cathode emission, an extra heavy glass envelope, improved grid/screen alignment and a higher plate voltage capability. This sets it apart from the conventional type sweep tubes.
Up until recently, very little data about practical application has been done on the EL509/6KG6 tetrode. Perhaps, to some extent, it has found its usage primarily among the so-called Hi-End audio applications and some in linear RF amplification.
At this point, discussion will be given on the device as a class C RF amplifier. In this case, the EL509/6KG6 lends itself well in this application.
During testing, an output power of 83 watts into a 50 ohm dummy load was easily achieved with 720 plate volts, 150 plate milliamps and a plate efficiency of nearly 78%! The frequency for testing was 1.24 MHz, as this was readily available. Similar results should be realized up to around 10 MHz or so.
Some comparisons were made between a 6146B and the 6KG6 tube as to power output and efficiency. The 6146B was chosen, as it is a familiar device for this application. The following data reflects these comparisons:
| 6146 | 6KG6 | |
| Plate Volts
Plate Current(mA) Screen Volts Control Grid(mA) Power Output(Watts) Plate Efficiency(%) |
650
110 210 4 51 71 |
695
150 155 5 81 77.5 |
Even though the output capabilities were different for each of the tubes, the comparisons were basically showing what each could produce within its own parameters. Notice that the plate efficiency is substantially greater for the 6KG6 in comparison to the 6146B.
In one test of the 6KG6, 100 watts output was achieved with a plate efficiency of 72%! This would probably be the power limit for this tube.
The 6KG6 is a well suited device for Class C service. This is a robust tube that is easy to drive with plenty of output power.
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**The information provided in this application note is intended for general design guidance only. The user assumes all responsibility for correct and safe usage of this information. Svetlana Electron Devices does not guarantee the usefulness or marketability of products based on this material.