DIY cardboard tube-radio kit

Franzis's cardboard DIY tube-radio looks like a hell of a fun way to spend a snowy holiday weekend; EUR50, including "nostalgic high frequency-tubes" and machine-translated instructions in charming pseudoenglish.

Make your own radio, combining the new and old technique together. The tubes works for strong reception and for the tube radios typical plesant sound. A modern Audio-IC and high class loudspeaker works for optimal volume. With this tube radio you can catch stations from all over the world. In fact you can also receive the ham-radio with this device. The tube radio has strong reception a modern world receptor. You can let yourself carried -off in the good old times, as to make your own radio normally. This packet contains all the necessary components

FRANZIS-TUBES RADIO FOR SELF CONSTRUCTION (via Make)

• [nixiebunny]

  There is a schematic diagram in the German instructions, but not in the Dutch instructions. Weird.

  This looks like a superregenerative shortwave receiver. These were commonly used for shortwave work before WWII and sometimes after, if the hobbyist couldn’t afford to buy five or six tubes and the associated coils.

  The radio is battery powered, using four AA cells for the filament and 9V for the anode.(!)

  This radio uses the single tube for all sorts of work – it oscillates, amplifies and detects the AM signal at the same time. Tuning is tricky and involves a lot of whistling (by the radio).

  These things radiate a lot of RF. I don’t think they’re allowed by the FCC these days. The manual has a paragraph about interference, but I’m not enough of a German reader to make out what they’re saying.

• [Michael Smith]

  Brings to mind a tube radio which my dad built from parts in the 1950s or early ’60s. We used to use it to listen to The Goons and The Science Show on the Australian ABC, well into the 1980s. I really should make sure he hasn’t thrown that old thing out.

• [PFlint]

  No one else wondered, “where’s the cardboard tube?”

• [Quibbler]

  How does it work? I’ve looked at the manual (ok I’m not very fluent in Dutch) where does the high voltage come from for the anode of the tube? Tubes also need a low voltage heater supply. There also appears to be no i.f. stage – is this a not a hetrodyne (maybe it is a regenative) – I think we should know before purchasing.

  • [Anonymous]

    The ‘high voltage’ for the anode of the tube is a 9 Volt battery.

    Jan Hamer

• [Roy Trumbull]

  The super-regenerative receiver predated the IF strip radio developed by Armstrong. And yes, they radiate like crazy.

• [Anonymous]

  I don’t see how they can call it a “tube radio” when it uses 2 transistors and an IC.

  The downside of using tubes for the audio output is that they’d have to have a real high voltage plate supply, not some feeble little 9 volt battery. Real battery portable radios of 60-70 years ago used one or two C or D cells for the filaments, and typically 45, 67.5 or 90 volt batteries for the plate circuits.

  Besides, homebrew sets like this should be built on breadboard with point to point wiring. Pre-etched PC boards are for wusses.

• [braininavat]

  > machine-translated instructions in charming pseudoenglish.

  Couldn’t they find the person who translated Roland manuals in the 80′s? Figuring out what they meant was part of the fun of getting your rhythm tracks going.

• [PFlint]

  No one else wondered, “where’s the cardboard tube?”

• [Roy Trumbull]

  I would guess this is a replica of a 5 tube AC/DC radio. They came along in the 1950s. The AC/DC feature didn’t mean much as few were served by DC power at that late date. What it did mean was that the set had no power transformer. No metal parts were on the surface of the box to prevent potential shock. Even the best ones always had a slight hum in the audio. The tube compliment had filament voltages that added up to 120 volts. The tube filaments were connected in series. Two typical tubes were the 35W4 and the 50C5. That took care of 85 volts. The remaining 3 tubes would have 12 volt filaments taking us up to 121 volts. Today you could buy a pile of solid state radios for the cost of those tubes.
  The fact that this radio has an audio IC negates its claim to being a tube radio.
  If you want that tube sound without tubes, look for an amplifier based on power FETs.