1920's Crosley Trirdyn

This is a 1920's Crosley Model Trirdyn AM regenerative receiver. The decal on the inside of the lid states this is a Trirdyn Regular Type No. 1121.

It is battery powered and has 3 tubes and is a regenerative receiver. The first tube is an RF amplifier - audio amplifier combination. The second tube is a regenerative detector. The third tube is the second audio amplifier that drives an external speaker. If using headphones, the third tube is not used. Tuning is accomplished by selecting one of 4 taps on the internal antenna loading coil and then turning the 2 large dials until the desired station is heard. Feedback for regeneration is accomplished by pulling the knob located in the top center of the front panel in and out. Pulling it out increases the coupling and therefore the feedback. Optimum operating point for regeneration is just at the point of oscillation. Below the feedback knob is a brass post that is pulled out/pushed in for the on/off switch for the tube filaments. The two knobs with the arrows control the voltage to the filaments for the tubes. The arrow knob on the left controls the filament voltage for the first RF amplifier - audio amplifier tube and the second audio amplifier tube. The arrow knob on the right controls the filament voltage for the detector tube.

This is a large radio measuring 21 1/4 inches long, 7 inches high, and 7 3/4 inches deep. The radio is not very heavy.

Below is a picture of the inside of the receiver.

The radio worked when I received it. All three tubes were good and the two original audio transformers had no open windings. And the radio works quite well. The first long distance station I heard was a station on 590 kHz in Atlanta, GA. With a little tuning, I was able to pick up WSM (650 kHz) in Nashville, TN very clearly with loud volume and good tone from the speaker. Nashville is 100 miles north of Huntsville. With a little more tuning I was able to receive WLW (700 kHz) in Cincinnatti, OH. The regenerative control is critical to tuning. If it is not adjusted correctly, a squeal can be heard and/or local stations will be heard in the background. At the point of regeneration, the selectivity is quite sharp and distant stations can be clearly heard over the local stations.

This only similarity between this radio and the Crosley 51 I have is the regenerative detector. Otherwise the design is completely different. The RF signal from the antenna is applied to a loading coil with 4 selectable taps (mounted on the left inside of the case as shown above). The output of the loading coil is applied to one of two selectable taps of the coil of a tank circuit. This tank circuit is tuned by an open air variable capacitor using the large knob on the left of the front panel. The RF signal from the tank circuit is direct coupled to the grid of the first tube where the RF signal is amplified and applied to a coil that couples RF into a second tank circuit.

The second tank circuit is tuned by another open air variable capacitor using the large knob on the right of the front panel. The RF signal from this tank circuit is coupled to the grid of the regenerative detector. The signal from the plate of the detector is fed back to its grid through the variable feedback or "tickler" control - the knob in the top center of the front panel.

Detected audio from the detector is coupled back to the grid of the first tube through an audio transformer. The first tube amplifies the audio along with the RF. The auido of the first tube is transformer coupled to the grid of the third tube. The third tube amplifies the audio and is direct coupled to an external speaker.

If headphones are used, the audio is taken off the plate of the first tube and the third tube is not used. Gain of the RF/first audio amplifier is controlled together with the gain of the second audio amplifier using the arrow knob on the left of the front panel. Gain of the detector is controlled using the arrow knob on the right of the front panel.

Tube Compliment

RF & 1st AF	Detector	2nd AF	Rider's Manual Page #
01A, X99, or 12	01A, X99, or 12	01A, X99, or 12	1-16

This radio has three '01A tubes installed and all are good. The '01A tubes use 5 Volt filaments. I used +90 Volts for the RF/1st AF and 2nd AF B+ and +22.5 Volts for the detector B+. The antenna I used was a 75 meter dipole but any long wire antenna will work well. A good ground is also necessary. I used an Atwater Kent speaker to listen. I experienced good performance with this setup.