As our loyal readers are aware, we often get off on tangents here at OneTubeRadio.com, but we always try to get back on track by showing actual One Tube Radios.  And the one we offer today has all the hallmarks of being an excellent performer, covering the range of 10-200 meters.

This is a one tube radio, since it uses a single 6F7.  But we’re cheating a little bit, not only because it’s a dual tube, but because the two halves of the tube are actually doing the work of three tubes.  The 6F7, which is still readily available at a reasonable price, consists of a pentode and a triode in the same envelope.  In this circuit, the pentode is used as an RF amplifier, with the triode serving as the regenerative detector.  But through the magic of “reflexing,” the pentode is then used a second time to serve as an audio amplifier.  The result is that the set gives the performance of three tubes, while only using a single tube.

The circuit originally appeared in the November 1933 issue of Shortwave magazine, in an article written by “well known shortwave engineer” Clifford E. Denton, who dubbed the set the “Triflex.”

For those wishing to duplicate the circuit, parts, or reasonable substitutes, should be readily available.  The new-old-stock tube can be found at this link.  You’ll probably need to make the plug-in coils yourself, but you’ll find helpful hints at this post.  Most of the other parts can be tracked down at my parts page.