6146B Beam Power Tube and Data Sheets (2024)

By Dr. Greg Latta, AA8V

The 6146 beam power tube and its variousdescendents (6146A, 6146B) was and still is one of the most populartransmitting tubes in amateur radio service. The tube was originally introducedby RCA in an ad in the January, 1952 issue of QST magazine:

With an ICAS plate dissipation of 25 watts a single 6146 could produce amaximum output on CW of 69 watts while operating with a plate voltage of only750 volts. This was remarkable compared to other tubes available at that time,which required higher plate voltages and/or higher driving power for the sameoutput. As the 1950s progressed and SSB began to replace AM as the preferredmode for phone operation, the tube proved ideal in linear amplifier service,and a pair of 6146 tubes in parallel became a very popular combination incommercial and homebrew SSB amateur transmitters.

12 years later, in the January, 1964 edition of QST, RCA introduced the6146B, a major revision of the 6146:

The 6146B featured a new plate design that allowed the ICAS platedissipation rating to be increased from 25 watts to 35 watts, a whopping 40%.As a result tube input could be increased by 33 1/3%! By simply plugging in a6146B in place of the original 6146, and raising the screen voltage from 160volts to 200 volts, (an operation that wasn't usually very difficult) atransmitter that originally had an output of 69 watts would now have an outputof 85 watts. Without circuit changes, the newer tube was simply more rugged,could take more abuse (as often occurred during tune up), and simply lastedmuch longer than the 6146. In SSB service switching a pair of 6146s to 6146Bsresulted in an even larger improvement. The result was that many of thecommercial tube transmitters from 1964 on featured a pair of 6146Bs in theoutput stage. In fact, one could argue that a pair of 6146Bs was the defactostandard in amateur transmitters until solid state gear began to replace tubegear in the 1970s and 1980s.

Despite what the above advertisem*nt implies, the 6146B is not alwaysa drop in replacement for the 6146/6146A. In some cases the slight differencebetween the interelectrode capacitances in the 6146/6146A and 6146B causesproblems with neutralization. Some transmitters originally designed for the6146/6146A do not have sufficient range on their neutralizing capacitors to beproperly neutralized when using the 6146B. These transmitters must have theirneutralizing circuits modified to obtain proper neutralization.

There is also a 6146W, which is a military version of the 6146/6146A or6146B. The trouble is that some 6146Ws are 6146/6146As, and some are 6146Bs! Ifyou are going to use a 6146W in place of a 6146B, be sure the 6146W your areusing is rated for service as a 6146B. If you are going to use a 6146W toreplace a 6146/6146A, then be aware that it might be a 6146B and you might havethe neutralization problem mentioned in the previous paragraph.

The 6146 series of tubes followed on the heels heels of the famous 6L6beam power tube, which was the first power tube touse the electron beam principle.

The 6L6 was released in 1936 and was first announced onpage 50 of the May, 1936 issue of QST magazine.The 6L6 revolutionized power tube design by forming the electrons into beamsand using aligned control and screen grids to limit grid and screen currents.Forming the electrons into beams increased the space charge near the plate,which then repelled secondary electrons back to the plate, eliminating the needfor a surpressor grid. See the diagram below. Other beam tubes eventuallyfollowed, including the 6146, 6146B, 6146W, 2E26, 5763, 813, 6V6, and others.

For more detailed information on the 6146 and 6146B beam power tube, clickon the links below to read the data sheets. You can also download the complete6146 and 6146B data sheets in PDF format.

6146B and 6146 Data Sheets:

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