Results tagged “tubes”

Radio 1946

Radio - Design, Production Operation, a technical magazine from 1946

I've always liked collecting old radio books and magazines, from kid's science project books to Popular Electronics.

Radio-April-1946-Cover-Blog.jpg

I enjoy reading the scans done by other radio freaks trying to preserve history, so here's a contribution from me, scanned several years ago. It's a trade magazine called Radio, with 56 pages, written for engineers and technical people. One could say it's like a 1940s version of Radio World.

I believe that this magazine came from the trash of Peter Granba here in Pittsburgh. In the 1980s there was a big curb side trash pile on a main road nearby, and the trove was so good that I asked my dad to drive me there so that I could pick up some of the radio-related items. Granba was apparently a Ham radio operator and electronics experimenter.

April 1946 contents include:

  • Cover: Western Electric's 'Clover-Leaf' FM broadcasting antenna
  • Inductive Tuned Loop Circuits
  • IF Amplifier Stability Factors
  • Electro-Mechanical Analogy In Acoustic Design
  • AM Transmitter Design
  • D-F For Static Pulses
  • Recent Radio Inventions
  • Bridged T And H Attenuators, Diode Conduction
  • Loss Due To Shunt Or Series Resistance
  • Capacitor Machine, Co-ax And TV, FM With Non-Linear L

In 1946, television and FM seemed to be well on their way, with the FM antenna tower on the cover, and high power FM, VHF, UHF and microwave tubes for airplane instrument landing being detailed. One advertisement is for the Eimac 3X2500A3 external anode tube, capable of 3500 watts output from 88-108 mhz, the modern FM band.

My favorite article is Modern AM Transmitter Design starting on page 30, which is about the latest 250 watt broadcast transmitter, as used in many communities across the country. It's fan-less, so it can be placed right in the studio, uses motorized final amplifier tuning, a high level plate modulator, and has a frequency response from 30 to 10,000 hertz.

250W-1946-AM-Transmitter-Blog.jpg
250 watt AM band transmitter

Get the full draft quality but readable PDF scan here:

Radio-Design-Production-Operation-1946.pdf

Boomer

Crosley radio

The story of my Crosley Model 125 'Litlfella' AM table radio, 1931-32

One day long ago I was hiking in a wooded area a few miles from my house, and came across a dilapidated little barn. One side of it was open and I peeked in and saw a big old radio sitting on a shelf, or a pile of wood. As you'd imagine, everything was gray with dust and webs, but I could tell what it was, I'd seen radios like it in old movies, where curved-top sets like that were part of the decor in parlor rooms.

I don't know why, but I left for home and came back later on my bike. I was around 11 or 12, and went everywhere on my one speed bike, so maybe I thought I couldn't carry a 17 pound radio all the way home without wheels. I sat it on the bike's seat and wheeled it home.

The Crosley had a couple of issues, the cloth behind the speaker opening was all torn up, though the speaker cone looked okay. A bigger problem was cracks in the '80' rectifier tube's glass envelope, which meant the radio couldn't possibly play without a replacement tube. My theory at the time was that since the power cord had been stored in the back of the radio, the plug had hit the tube, but I'll never know for sure.

For a speaker cloth, I went to mom's fabric box, where she kept lots of carefully folded scraps for patches to mend clothes with. I got something I thought would look good in the radio, took out the speaker and put the cloth in front of it. It looked a little like Hawaii, but I thought it was okay at the time, and I'm glad I put it in, since it's protected the speaker cone from damage over the years.

crosley-model-125-01.jpg

After that I stored the radio on the bar top in the basement, waiting until I could get an 80 tube for it. At the time I wasn't connected with the radio scene or collectors, so I didn't know how to get a tube, just thinking antique stores might have it, or I'd find another radio that had a good 80, but I never did. Years later I was at a radio gathering and made friends with someone who had an 80 tube, and he offered to send it to me free of charge! Thanks Workingman.

The new 80 brought the radio to life, the tubes lit and it had some hum and a scratchy volume control, but in spite of that the tuner was able to pull in a few local stations, weak but listenable. I put the radio away again and thought that sometime later I could restore it more. I was writing with a friend at Hobby Broadcasting's blog about his old radio restorations, and he mentioned that radio companies have made replacement speaker cloth for these old radios more recently, and asked what kind model of Crosley it was. I didn't know and went to check, and thought I might as well do a photo shoot while I was at it, inspiring this article.

It's interesting to think about the history of this radio, how it probably sat in someone's parlor and was the main source of electronic information a household would have at the time. Television wouldn't come to Pittsburgh for another 16 years yet, 1948.

Related links:

Here's a small gallery with more pictures of my Crosley:

http://boomerthedog.net/crosley/crosley-model-125.html

Someone has restored their 125, different cabinet, looks to be the same chassis:

http://mcclellans.com/Crosley125LitlfellaRestoration.htm

The 125's schematic:

http://www.nostalgiaair.org/PagesByModel/413/M0043413.pdf

Hobby Broadcasting's blog

http://hobbybroadcasting.blogspot.com/2014/02/philco-87-restoration-blog-thread.html

Boomer