I’m often asked what a TRF radio is. TRF stands for Tuned Radio Frequency and these radios were standard design before the superhet radio appeared on the market. I won’t go into the technical details here as it’s not necessary. Some people buy TRF radios on auction sites and then wonder why they can only pick up a few stations, or they find that stations are very difficult to tune in. TRF radios worked well and, with only three or four stations on the medium wave band, they were easy to tune in. Their selectivity, the ability to separate stations on the dial, was fairly poor. But this didn’t cause problems as there were only a few stations on the medium wave band at the time, and they were spaced fairly wide apart. As the medium wave band became crowded with stations over the years, the TRF radio would often tune in to two stations at the same time – so a new design had to be developed. The superhet radio is far more selective than the TRF design and is able to separate stations even when they are very strong and close together.
Some of the smaller TRF radios come with a ‘throw out’ wire aerial fixed to the back panel. This wire should not be lengthened as it might upset the alignment of the tuned circuits. Such radios were only meant to pick up a few local stations, not distant weak stations so leave the aerial as it is. I wouldn’t advise buying a TRF to use as an every day radio. They are lovely radios for collectors but, if you want to tune around the medium wave band and listen to various radio stations, then get yourself a superhet radio.