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The Rise of Radio Engineering 1920-29

Contrast of Two Great Radio Manufacturers- Atwater Kent vs Crosley

Atwater Kent Radios

Atwater Kent was a bright inventor and smart investor. He invented the point-distributor ignition system which is still the basis of car ignition. He is also famous for the breadboard radio (highly collectible). Atwater Kent made high quality radios and when the depression came he quit because he wouldn't make cheap radios to save money. Even though Philadelphia was his love he retired in Bel Air, CA, where his house still stands and his money was left to Philadelphia in the arts and culture.

1. Atwater Kent 20 (the Big Box) 1924- TRF radio using UX-201 and a UX-200 Tubes. AK before the rise of Zenith was the premier radio to own. $80 (1924)

BELOW:AK 20 with cabinet removed design based on the AK10 Breadboard. The tube sockets can accommodate older UV and UX based tubes.

2. Atwater Kent 33 a 6 Tube Battery Set for 1926-27 model year.  Uses 3-UX201A's as RF amp, UX200 detector, UX201 audio driver and UX112A audio output. The model 33 represents final upgraded TRF battery sets by AK. The radio features single knob tuning and antenna tune.

Compare the 1926 AK 33 layout to the 1924 AK 20.
BELOW: Metal drive belts used to gang the three adjustable tuning capacitors together.
Typical setup for radio operation. Left of radio is the A-B-C battery set. The A battery is a secondary 6 V while the B and C batteries are primary 90 v, 67 v, 22,5 v and 4.5 v batteries.

3. Atwater Kent 42 (the Bread Box) 1928 with matching E speaker. Early AC operated TRF radio Use UX-226, UX-280 and UX-171A tubes


BELOW:INSIDE an EARLY AC OPERATED RADIO The tube and black box is the power supply!

                                     Crosley Radios

Powell Crosley and his brother Lewis were  bright and resourceful business people. Their approach was to make affordable radios. Crosley radios are minimalist designs. Get the max from the minimum. Crosley survived the Great Depression which allowed them to invested in other ventures like appliances, cars and even a baseball team the Cinncinatti Reds. They made it into the mid 1950's.

3. Crosley Model 50, 51 and 52 Regenerative Receivers (1924) using Crosley patented Spider Web and Book Tuning Capacitor design. $14.50, $28.50 and $30 respectively (1924)


BELOW:Top: Model 50, Left Bottom: Model 51, and Right Bottom: Model 52 
Crosley 50 (1924)- 1 Tube Regenerative Receiver. UV / UX-201 grid leak detector and amplifier
Inside the Crosley 50. The key to their low cost amd popularity of the Crosley 50, 51 and 52 is the simple Book Capacitor that is compact and simple. Capacitance adjustment is done by opening and closing the plates with a rotating cam.. The Spider Web coils for regeneration and coupling. One coil is stationary while the tickler coil moves in and out.
Crosley 51 (1924)- 2 Tube Regenerative Receiver. UV / UX-200 grid leak detector, UV /UX-201 audio amplifier. Will accept UX-199 tubes with correct adapters.
Inside the Crosley 51. Note the extra vacuum tube and audio transformer (upper left) for greater output volume.
Crosley 52 (1924)- 3 Tube Regenerative Receiver. UV / UX-200 grid leak detector, UV /UX-201 amplifier and UX-201 Audio Output for speaker output. Will accept UX-199 tubes with correct adapters.
Inside the Crosley 52. ABOVE: the audio transformers (upper left) Spider web tapped coil, spring loaded book tunning capacitor provides tuning and regeneration and the grid leak capacitor and resistor (upper right). BELOW: Showing the typical bus wire interconnections of that time period.

4. Crosley Super Trirdyn Regular. Runs on Batteries (1924). Uses 3 tubes and two sets of adjustable spider web coils.

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SHOWCASE: 1920's Radio Electronic Restoration

Replacing capacitor and resistor in the Atwater Kent Model 20 (1924)  TRF Radio

Capacitor: The phone capacitor was open (Value 0.002 uF). Shown below are the steps from original to replacement. From left to right.

Resistor: One of the tube grid damping resistor was way out of tolerance. Should be 600 ohms but read 500,000 ohms. Shown the addition of a modern 680 ohm resistor in parallel and the final product.