Retrotechtacular: Fog Over Portland

In the early days of broadcast television, national spectrum regulators struggled to reconcile the relatively huge bandwidth required by the new medium with the limited radio spectrum that could be allocated for it. In the USA during the years immediately following World War Two there was only a 12-channel VHF allocation, which due to the constraints of avoiding interference between adjacent stations led to an insufficient number of possible transmitter sites to cover the entire country. This led the FCC in 1949 to impose a freeze on issuing licences for new transmitters, and left a significant number of American cities unable to catch their I Love Lucy or The Roy Rogers Show episodes.

The solution sought by the FCC was found by releasing a large block of UHF frequencies between 470 and 890 MHz from their wartime military allocation, and thus creating the new channels 14 to 83. An experimental UHF pilot station was set up in Bridgeport, Connecticut in 1949, and by 1952 the FCC was ready to release the freeze on new licence applications. The first American UHF station to go on air was thus KPTV in Portland, Oregon, on September 18th of that year.

UHF TV was a very new technology in 1952, and was close to the edge of what could be achieved through early 1950s consumer electronics. Though the 525-line TV standard and thus the main part of the sets were the same as their VHF counterparts, the tuner designs of the time could not deliver the performance you might expect from more recent sets. Their noise levels, sensitivity, and image rejection characteristics meant that UHF TV reception  did not live up to some of its promise, and thus a fierce battle erupted between manufacturers all keen to demonstrate the inferiority of their competitors’ products over the new medium.

The video below the break delivers a fascinating insight into this world of claim and counter-claim in 1950s consumer electronics, as Zenith, one of the major players, fires salvos into the fray to demonstrate the superiority of their products over competing models or UHF converters for VHF sets. It’s very much from the view of one manufacturer and don’t blame us if it engenders in the viewer a curious desire to run out and buy a 1950s Zenith TV set, but it’s nonetheless worth watching.

A key plank of the Zenith argument concerns their turret tuner. The turret tuner was a channel selection device that switched the set’s RF front end between banks of coils and other components each preset to a particular TV channel. Zenith’s design had a unique selling point that it could be fitted with banks of components for UHF as well as VHF channels thus removing the need for a separate UHF tuner, and furthermore this system was compatible with older Zenith sets so existing owners had no need to upgrade. Particularly of its time in the video in light of today’s electronics is the section demonstrating the clear advantages of Zenith’s germanium mixer diode over its silicon equivalent. Undeniably true in that narrow application using the components of the day, but not something you hear often.

Here at Hackaday we have a fondness for the analog TV and radio technology of  yesteryear, as for more than one of us it’s how we got into electronics. In the past we’ve featured videos on the first remote control TV from RCA as well as the manufacture of TVs in 1959, and if it’s Zenith that have piqued your interest here we featured an early Zenith FM radio when we looked at restoring tube radios.

23 thoughts on “Retrotechtacular: Fog Over Portland

  1. I easn’t previously aware that the Zenith turret tuners of that era allow for the change out of strips to customize the tuner to available stations in a market.. By the time I entered TV servicing terrent tuners and wafer switch tuners had no real advantage of one another. There was on terrent tuner where after a time yo had to bend the contact strips into position, and turn the tuner in on direction only because turning it in the other would bend the contact strips again, resulting in noisy connections. other than doing that trick on that particular turret tuner we send the tuners to a specialty shop for reconditioning, because few dealer or independant repair shops didn’t have the equipment to align the tuners in a time effective manner. Somewhere around here I have a portable 12″ Sanyo B/W TV with a turret tuner. Something satisfying about the feel of turret tuner, like the satisfaction of punching the buttons on the older car radios. I suppose no matter how light the effort manual labor brings satisfaction. The simplicity of programming the mechanical car radio tuners can be beat.

      1. Clearly a converter made more budget sense. I’d have to assume Zenith also marketed converters as well to cover all bases. Perhaps that had some sort of exchange or “trade in” program for the UHF turret strips?

      1. I think he forgot the non-meteorological definition.

        Fog definition #2.
        Something that obscures and confuses a situation or someone’s thought processes.
        “the origins of local government are lost in a fog of detail”

    1. Very interesting stuff starts at:
      8 minutes, 20 seconds.
      Worth a watch, some bad acting too!

      Intriguing video!
      Very different broadcast issues back then; WW2, FCC, New amazing state-of-the-art tuner tech…
      Let’s cut down a wide swatch of the forest, my TV is only picking up static! ;)

  2. That was the longest ad I have ever watched online. I’m actually a little impressed. Nice find hackaday.

    Those strips…. There’s gotta be a modern equivalent waiting to happen somewhere….. single board computers on a rotary hdmi selector?

    1. That would be kinda cool!
      How about NES, SNES, Atari, N64, ect. game ROMs outside of their cartridges. Turn a giant knob *click, click, kerCHUNK*
      Street Fighter starts up. Ready to play!

        1. Bah. Wouldn’t be me though. Love the tech, haven’t played the games in almost 2 decades.
          I’m getting more ideas on this though.
          I’ll want to grab an 80’s TV and hack the tuner to be a resistance selector, or something. Been a long time since I’ve come across one!
          I loved this, Jenny. Seriously great retro find!

      1. A rotary encoder and an emulator that can save and load state quickly would let you switch games as fast as you could switch analog channels. Could be fun.

        1. And the whole thing could look like a stock vintage set if done properly.
          Somebody make this!
          I don’t have the time to attempt it and learn coding at the same time. Too much overtime at work until Autumn comes around. This is going into my idea notebook.
          I will keep an eye open for projects for the ‘SD card rotary switch’ and throw suggestions at the first few, if anybody makes an attempt. :)

          1. Step one: Figure out an emulator that can save and load state from the command line, or sufficient xdotool foolery to fake it. Step two: Make a rotary encoder trigger stopping the current emulator and starting a new one, either the previous or next in the folder list depending on wheel turn direction (udev can probably do this, or maybe something like autohotkey). Step three: Hack hardware into retro tube TV and pray to bob it has a composite input or a hack available.

          2. @not a space lizard I know that would work, but I’m thinking or using multiple EPROM’s. No Arduino or Linux etc. preferably. :) At least for the final version.

            First prototype would output analog channel 3, if I can do it, and yeah it would be using some emulator.
            This could be awesome…

    2. Okay. Very dirty hack, data loss expected for this idea.
      Rotary HDD selector! IDE would be a nightmare to attempt. Or…

      SDcard selector. I think it would actually be doable, maybe someone already has. (I just searched, found nada.)
      Put the ROMs in them. :)

  3. Once those plated metal contacts went, it was a spray job every month or so. We had a channel 18 strip for our 12 channel set but it didn’t seem to work well. I still don’t know how they did it with out active electronics. Then we got cable in the mid 60’s and it wasn’t needed at all. I would take the detent out and make it easier to turn and park on a better spot than the worn spot set by the detent. Some knobs would split in two because of such stiffness, and I can remember more than one set-top pliers. Sometimes the half moon shaft would be worn down such that a new knob wouldn’t stay on. Yes they sold many replacement knobs.

  4. I recommend PF Reporter magazine on American Radio History ( The magazine grew up with TV technology and published from 1951 all the way to the end of the CRT era in 2000. Most tuners were made by a small number of companies, notably Standard-Kollsman; the turret tuner was a de facto standard. Interesting enough, the electronic varactor tuner is surprisingly old–the same firm built an experimental electronic tuner in 1969!

  5. UHF was a huge flop for many reasons.
    1. The early tuners where so bad that you had to have one or two channels between each station.
    2. It took years for the FCC to require all TVs to have UHF tuners so you had a chicken and egg issue. The networks worked really hard to keep VHF channels because they wanted large audiences. TV companies didn’t want to put in the tuners that customers really didn’t want.
    3. UHF has a shorter range than VHF.
    It is a real shame that it did not work out. It might have prevented the rise of the cable company.
    Of course today we have solved most of the problems of broadcast TV with the digital. The problem is that cable companies pay to carry the networks so networks have no interest broadcast. I live in a city of around 200,000 people and I can get one network channel. It is not the cost because I also get several religious and spanish channels.

  6. I find the turret tuner interesting, being able to replace strips to get different channels, I suppose the store, tv repairman did that? But it also must have meant new channel, new strip, and I’m sure there was a limit to the number of strips you could have in the turret. Crazy old technology, it sure isn’t SDR! Anyway here’s another interesting documentary in UHF, enjoy.

    1. You ass.
      Weird Al just jumped the crap out of me!

      That is a great video!
      I didn’t know that ‘Mr. Weird’ did a series on VH1 about the historical accuracy of radio and television broadcasting in the 1980’s. Awesome find! Trollolo

      I think some CB/ham radios did this as well. My Grandparents had a ‘scanner’ so they could hear the police and fire bands. He took the top off one day and showed me. Like 16 spots for crystals. It’s probably what got me interested in electronics.
      Wish that first frame wasn’t a closeup! Lol.

  7. The Zenith ad doesn’t just claim that germanium diodes are better than silicon, it also claims that triodes are better than pentodes, a single superheterodyne receiver is better than a double superheterodyne receiver, and that sets with continuous tuners have nightmarish drift problems. I smell marketing bullshit.

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