I know early radios were powered from batteries because AC could not be used with the filament-type cathodes of early tubes. This problem was solved when insulated cathode tubes were developed. Can someone tell me when this was and when the change over from battery to AC-powered sets occurred?

Hi Nat

In 1927 the #27 tube was available (5 pin). It was the first popular triode with a cathode. Kellogg and others made triodes with cathodes. These all had 4 pins and were never very popular. Some used top or side connectors for filaments. Arcturus tied the cathode to one filament lead.

Norm

: I know early radios were powered from batteries because AC could not be used with the filament-type cathodes of early tubes. This problem was solved when insulated cathode tubes were developed. Can someone tell me when this was and when the change over from battery to AC-powered sets occurred?

Thanks Norm

Can you tell me who introduced this #27 tube? I would assume there had to be other AC tubes before a complete radio could be AC-powered so at what point did the AC-powered radio become standard?

And can you tell me when super-het designs replace TRF type radios?

-Nat

:Hi Nat
:
: In 1927 the #27 tube was available (5 pin). It was the first popular triode with a cathode. Kellogg and others made triodes with cathodes. These all had 4 pins and were never very popular. Some used top or side connectors for filaments. Arcturus tied the cathode to one filament lead.
:
:Norm
:

Hi Nat

A good book on tube history is 70 Years of Radio Tubes and Valves by John W. Stokes. RCA announced the UY227 in May 1927 but didn't make their own tubes.

AC power radios became standard around 1927 with Atwater Kent Model 37 and RCA Radiola 17 & 18. Others like Sparton made AC radios with Kellogg or Cardon tubes. These were TRF.

There were superhet radios along with TRF's in the 1920's. Performance was bad on superhets. Stations would be heard two places on the dial along with hetrodyne squeals. RCA made superhets like AR-812 which was so bad they went back to TRF. These radios had tubes & coils lined up in a row so would oscillate easily. The oscillator stage didn't have any protection. If it stopped the tube would burn out since there wasn't any series resistance in the circuit. RCA came out with a protection device, UV877, which was supplosed to protect the radio from incorrect battery hookup. It was really there to protect circuits when something went wrong.

Adding extra bypass caps to some early superhets helps but not the entire answer.

Superhets did get better and very early 1930's became popular. The first osc/mixer tube, 2A7, was out in 1933. There were good superhets before this tube. Atwater Kent used 57 pentode before the 2A7 was available.

Norm

:Thanks Norm
:
: Can you tell me who introduced this #27 tube? I would assume there had to be other AC tubes before a complete radio could be AC-powered so at what point did the AC-powered radio become standard?
:
: And can you tell me when super-het designs replace TRF type radios?
:
: -Nat
:
:
::Hi Nat
::
:: In 1927 the #27 tube was available (5 pin). It was the first popular triode with a cathode. Kellogg and others made triodes with cathodes. These all had 4 pins and were never very popular. Some used top or side connectors for filaments. Arcturus tied the cathode to one filament lead.
::
::Norm
::
:

Thanks Norm. You have been very informative. I've been fascinated with radios since I was a kid and someone gave me a old Hallicrafter S-20R communication receiver. I managed to get it going which led me to become a ham, open a radio repair business (at 15), then became engineer at a local radio station which lead to a long career in broadcast engineering. I'm pretty familiar with technology since the 1950s, but for some reason I've become intrigued with what came before- particularly 1920s transmitters and receivers. I'm glad I found this forum and hope maybe I can help out with questions about the newer stuff.

- Nat