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The Rise in Radio Engineering 1920-1929
Radio Speakers and Accessories
Radio Speakers and Accessories
Radio Speakers
Radio Speakers
These were optional. Until the latter part of the 1920's, radio listening was generally from a set of headphone. The radio speaker was an expensive option. So if it took months to save up for a radio, the addition of a speaker was take even longer. With the rapidly changing technology radios and speakers will become obsolete quickly.
Atwater Kent E (1924) Sold as an accessory for AK's that can drive a speaker such as the model 20 with a UX112 power triode as the final output tube. As better audio tubes came out AK updated the E series as well. A moving cone speaker, fore runner to the voice coil speaker.
RCA 100A (1927) Originally designed for the RCA Radiola 17 and 18. Replaces the RCA 100 and was a major step in speaker design. This speaker is an example of a cone-voice coil design providing better sound dispersion and reproduction. Price $29 in 1928.
Below: RCA 100A Cone Speaker
RCA UZ1325 Horn Speaker (1923), was a accessory for all RCA Radiolas capable to drive a speaker). A horn speaker was basically a modified headphone with a large passive sound radiator. Price $25 in 1923.
Rear side of the AK Model E.
BELOW
RCA 103 (Tapestry Speaker) 1928. Originally designed to pair with the Radiola 60 AC operated Superheterodyne. Speaker technology is similar to the RCA 100A. Unlike the metal cased RCA 100A, this model was a wood framed octagon shape and the back was furnished a hardboard speaker cover and a silk shroud bonnet to allow cleaning. Price $37.50 in 1928.
My Magnavox M-20 BELOW: Sometime in tghe past, a different speaker panel was substututed and the cabinet stripped but never completed. In order to duplicate the original panel a lathe is needed, which is expensive, so I tried to get close using premanufactured parts and I had a grille cloth that is close. So I made a new speaker panel with mahogany veneers.
RIGHT: ID Tag restored. BELOW: M-20 Horn Unit
Sonora Radio Speaker (1924) Sonora then a phonograph company formed by George Brightson sold speakers as an accessory to widen their market into radio. This is a horn type speaker. Price $30 in 1924.
Magnavox M-20 (1925) Oakland CA. Cabinet Loudspeaker ($25 in 1925) Originally a speaker accessory for the Magnavox model 10 radio. Magnavox was formed in 1917 by Peter Jensen and Cyril Elwell making speakers and amplifiers.
Photo of original unit (not my collection) from WorthPoint site.
Battery Eliminators and Chargers
Battery Eliminators and Chargers
Immediately after radios were being sold, the batteries became an expensive part of ownership. As technology in vacuum tubes permitted, battery eliminators replacing the B or power source and chargers to recharge rechargeable A or filament source were made available.
Tube Rejuvenator
Tube Rejuvenator
Jefferson Tube RejunvenatorJefferson Electric Mfg Co, Chicago IL
Like A batteries, replacing vacuum tubes were expensive. As vacuum tubes age due to continued use, the electron emission from the filament declines, due to the slow oxidation of the metal. This device adds extra like by providing a higher filament voltage, removing the oxidized coating, thus improving electron emission. Usually good for one more time, cannot repeat the process.
Jefferson was also a transformer maker and was in business for most of the 20th century.
ABOVE: Instructions on the front label. BELOW: Inside rejuvenator after partial restoration. Note the potted transformer (120 VAC to 18 VAC secondary tapped to provide the filament voltages for flash and aging the filaments.
Tungar Bulb Chargers
The Tungar Bulb was the first electronic device extensively used for charging batteries. Rechargeable A Batteries were popular because of the high cost of replacing these batteries to run the vacuum tube filament. For more details on Tungar Bulbs and Chargers go to this link in my website:
LINK: TUNGAR BULBS AND CHARGERS
RIGHT: A typical A Battery Tungar Bulb Chargermade by General Electric- the inventor. BELOW: Watch Tungar Charger demonstration.
Tungar Bulb DEMO (convert-video-online.com).movThe Jefferson can rejuvenate up to 2 tubes. Has low and high filament selection for flash mode and aging mode. When purchased- was modified to handle 2 UX-201A TUBES ONLY. I return the rejuvenator to test 201/201A tubes and 120 / 199 tubes. To test UV base, I found adapters that will plug into the sockets.
ABOVE: The rejuventaor board as found and then partially restored. BELOW: X201A tube at fillament aging stage after flash mode completed.
Video Demonstrating rejuvination process on a X201A tube.
Jefferson ElectricTube Rejuvenator.mp4
Battery Eliminator
Valley B Eliminator (early-mid 1920's)Valley Electric, St Louis MO
The B Battery or power supply source usually lasted much longer than the A Battery, but that didn't stop manufacturers from offering B vol;tage alternatives. Think of this as today's battery eliminator you plug into the wall socket.
The B Battery or power supply source usually lasted much longer than the A Battery, but that didn't stop manufacturers from offering B vol;tage alternatives. Think of this as today's battery eliminator you plug into the wall socket.
BELOW: This eliminator uses a tapped transformer fed into a UX-280 full wave rectifier which is filtered by a capacitor. The B+ outputs are 22, 45 and 90 VDC and filament power for detector and all other tubes.
The Valley Eliminator has 3 B+ terminals plus two filament adjustments.
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