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Winter 2004 Issue |
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Russian Power Tubes in Amateur Radio, Part II In the Fall 2003 issue of CQ VHF, ND2X began this two-part article on Russian power transmitting tubes, covering general information and triodes. This time he continues with a discussion of tetrodes and sources of tubes. By Paul Goble, ND2X |
 The GS-3A tube. |
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As was stated in part one of this article, I
have been the beneficiary of information on Russian power tubes from some
extraordinarily knowledgeable hams from QTHs ranging from my home state of
Texas, across the U.S., west to Japan, and east to eastern Europe. We
covered triodes last time and will now move on to tetrodes. The tetrodes I
will cover are the GS-3A, GS-15B, GS-23B, GS-36B, GU-43B, GU-74B, GU-78B,
and GU-84B. There is tube-specific information gleaned by this author,
either as empirical measurements or from specific experiences of hams
around the world. GS-3A: The GS-3A tetrode (photos 21 and 22) is designed for water-cooling; no air cooler is associated with this tube. It is rated at 3000 watts of anode dissipation to 800 MHz. All indications are that the GS-3A should perform well from 70 cm down. Internal construction appears almost primitive, with large bolts holding control and screen grid cages in place. Photo 23 shows the coaxial arrangement of the tube elements. At this writing, this tube is under investigation. A water-cooler design is presented at <http://www. nd2x.net/kd5fzx-gs3aH2O.html>. Results of the design and prototype of a 70-cm PA will be “published” at <http:// www.nd2x.net/kd5fzx-gs3a.html> when testing has been completed and data are available. This tube is priced at around $50 plus shipping, when it can be found. Pictures of the GS-3A, the water cooler installed on the tube, and the internal structure are shown in photo 7. GS-15B: The GS-15B (photo 24), another of the newer generation of Russian tube designs, is just under 2.5 inches tall and less than 1.5 inches in diameter. It has a designed tube life of over 2000 hours. It is a planar tetrode with a cathode diameter of 11 mm, and it can support currents of 400-plus milliamps in amateur service. The grids are flat sheets with window openings that are in line for low intercept, resulting in very low grid currents. Small physical size indicates that the GS-15B might be useful well beyond the 1-GHz specification. Tests also show that the filament voltage specified for 6 to 6.6 volts (6.3 volts, nominal) can be run at 5500 volts without decreasing emission and will likely extend the indicated 2000-hour tube life.
Sockets are not available and are constructed
as part of the PA designs in which this tube is used. The anode cooler
cannot be detached, but an effective water cooler has been developed in
spite of this and is presented at <http://www.
nd2x.net/kd5fzx-gs15H2O.html>. The GS-15B has been available for $10 to
$25, depending upon the source. It is used in the current Russian
equipment inventory, and it is increasing in price to the amateur market. |
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