Trirdyn special

The Trirdyn Special is similar to a straight Trirdyn except for the vernier tuning and the RF amp was changed slightly. It is a 3-tube radio built in 1924. This is a unique radio as it incorporates some interesting technical features. The Trirdyn is a regenerative and also has a reflexed stage. The signal path is as follows:
The signal comes into the antenna terminals. It is then amplified (RF) thru the first tube. This is a TRF stage tuned by the left tuning knob. It is then coupled to the regenerative detector stage tuned by the right tuning knob. The audio output of the detector is transformer coupled back into the first stage which doubles as an audio amp. The audio output of this reflexed audio amp is transformer coupled to the audio output amp which drives a horn nicely even on the weakest signals.

The sensitivity of this set is very good, capable of getting down to the background noise. It is a little trickier to tune than the typical TRF set however. If the filaments are lit too hot, the gain increases until a nasty howl results. This howl is due to the reflexing nature of the set. Proper operation suggests to use only as much filament that is necessary to receive the desired station with adequate volume.