The tuning knob and dial cord mechanism work very well right out of the box. On one of my “hot rod” units, I replaced the silk-screened dial with a plain piece of Plexiglas backed with a hand-calibrated dial, which permitted accurate calibrations for 10-kHz channel identification. Although I don’t recall ever having tried it, the circuitry could possibly be coaxed to 1700 kHz. The radio was designed prior to the expansion of the AM broadcast band to 1700 kHz thus, it is only specified to cover 520 kHz through 1620 kHz. The picture below shows the dial of the -656A. The internal layout was not especially good for repair or modification, but at least was well within this enthusiast’s capability. On final clearance this dropped to $25, and I snapped up several for my friends and my own tinkering. In later times, the -656A retailed for $34.95. Consequently, my comments are mostly focused on the 12-656A. I didn’t discover these treasures until late in their production cycle. Further, the radios were AM only uncompromised by FM circuitry, which would have to be integrated into the design and provide a distraction at best and a performance compromise at worst. The TRFs were by no means the first radios to have this feature, but they were obviously marketed to folks who wanted longer than normal distance reception. The term TRF was a throwback to the days of the tuned radio frequency radios and referred specifically to Radio Shack’s addition of an extra RF amplifier ahead of the converter stage. Obviously, this required more circuitry and, consequently, more expense.Įnter the Radio Shack TRFs. Better, more sensitive radios added a third stage, an RF amplifier operating ahead of the converter stage. This was standard design practice during the vacuum tube and transistor eras. Entry level (read cheap) radios were limited to two stages consisting of a converter and an oscillator. Eventually, designers hit on the idea of mechanically connecting all the RF stages together so tuning could be accomplished with a single knob.įast forward to the standard AM radios of a later generation. As amplifier stages became cascaded in two or three stages, this became a real problem, as each stage had to produce the correct frequency before anything could be heard. In the early days of radio, the term referred to the necessity for the operator to manually put an RF amplifier stage on frequency by adjusting the value of a variable capacitor or inductor. TRF stands for tuned radio frequency receiver. These radios were commonly known by their sobriquet “TRF.” Initially applied by Radio Shack itself, the term stuck. I remember them being very popular among National Radio Club members of the time. These were identified respectively by their Radio Shack stock numbers 12-655 and subsequently the 12-656A. In the late 1970s and the early 1980s, Radio Shack provided an attractive answer to this conundrum for medium wave DXers. At the same time, most of us don’t want to sacrifice any more capability than necessary. There has always been an interest in DXing on the cheap. Many thanks to SWLing Post contributor, Bob Colegrove, for the following guest post:
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