1924 Crosley 51

This is a 1924 Crosley Model 51 AM receiver. It is battery powered and has only 2 tubes and is a regenerative receiver. The first tube is the regenerative detector and the second is the audio amplifier. Tuning is accomplished by selecting one of 5 taps on the coil and then turning the large dial until the desired station is heard. Feedback for regenration is accomplished by pulling the knob to the upper right of the large dial in a out. Pulling it out increases the coupling and therefore the feedback. Optimum operating point for regeneration is just at the point of oscillation.

This is a small radio measuring only 11 inches long, 6 1/4 inch high, and 4 3/4 inches deep. I also have the original operating instructions for this radio. See below.

Below is a picture of the inside of the receiver. Note that the warranty card is still attached to the lid.

This radio has a open winding in the primary of the audio coupling transformer. To make the radio work I made the following modification:
I placed a 10k ohm resistor across the open widing to provide B+ to the detector tube. I connected the primary to the secondary through a 0.1 uF capacitor to couple detected audio to the audio amplifier.

The radio works now. And it works quite well. The first long distance station I heard was WLW in Cincinnati, Ohio, which is appropriate since the radio was made there! With a little tuning, I was able to pick up WSM in Nashville, TN very clearly with loud volume and good tone. Nashville is 100 miles north of Huntsville. 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.

Tube Compliment
AF Amplifier
Rider's Manual Page #
'71A or X'99
20 or 12

This radio has two '01A tubes installed and both are good. One has a date of purchase of 1934. The '01A tubes use 5 Volt filaments. The instructions indicate when using '01A tubes, you use +90 Volts for the audio B+ and +45 Volts for the detector B+. I used the battery connections (Figure 1) in the manual for 6 Volt tubes. 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 my Trimm "Featherweight" headphones to listen. I experienced good performance with this setup. Below is a picture of my receiving setup. You can see my homemade power supply next to the radio.