4D32 rig is back!

Discussion in 'Amplitude Modulation' started by N2DTS, Sep 2, 2016.

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  1. N2DTS

    N2DTS Ham Member QRZ Page

    Took the screen modulator and 2x 4x150 rf deck out of the rack and plugged in the 3x 4D32 rf deck and the 811 modulator back in.
    Does 300 watts carrier, and its silent, no fans at all.[​IMG]
    N6YW likes this.
  2. WA3VJB

    WA3VJB Ham Member QRZ Page

    Brett, I've always loved the rugged look of the 4D32. I have only experienced them with my Collins 32V2, and I've wondered whether the model nomenclature came across from that of the tube itself.

    Another possible connection is with the appearance of the "Star Wars" character R2D2. When I first saw that creature and name, I immediately thought it looked like a 4D32 with mobility.


    The RK-4D32 has remained plentiful on the NOS market. Yet, 40+ years ago I was told by my "Elmer" that I should seek out some spares when he sold me the transmitter. So I did, and after testing and labelling them, they've been knocking around the shelves for more than 40 years on their own.

    It's a strong tube. I think I've only had one go soft, and I noticed it only on 10 meters!
  3. N2DTS

    N2DTS Ham Member QRZ Page

    A rugged tube.
    I run them at 1200 or more volts plate modulated, never an issue.
    Three will do 300 watts easy, no fans.
    As a lower voltage tube, they work well with 811's.

    I have a bunch of them, only one is bad, its got a piece of metal floating around in it, a support of some kind, and in the old days before they got cheap, I used to shake the tube till the metal was resting on the side of the cathode support and use it (it worked fine).

    I wonder if anyone ever tried triode connecting them in audio service...
  4. K9STH

    K9STH Ham Member QRZ Page

    The Hallicrafters HT-20, the Collins 32V- series, and the Johnson Viking I are the only commercial amateur radio transmitters, that I can "think of", that used the 4D32 tube.

    With an HT-20, one can load the transmitter into a dummy load to 100-watts output, lock the key, come back weeks later and the transmitter will still be putting out 100-watts! The tube is definitely extremely rugged.

    The Collins 32V- series, and the Johnson Viking I, are pretty common. However, not so the HT-20. The HT-20 is rarer than the "matching" SX-88 receiver. There were around 200, maybe as many as 300, of the HT-20 transmitters manufactured. My HT-20 is s/n 11.

    Glen, K9STH
  5. N2EY

    N2EY XML Subscriber QRZ Page

    Years ago, I read a story about the 4D32.

    Seems it was a pulse modulator tube developed during WW2, and only made by one or two manufacturers. The reason so few amateur transmitters used it was that the 6146 came out about 1951 and became the go-to tube for amateur transmitters between about 60 and 180 watts input.

    The story continues that 4D32 production continued for a few years in the 1950s or so, but then shut down. So the supply of 4D32s was slowly used up, resulting in high prices and scarcity.

    And then....sometime in the 1990s?.....somebody discovered a government warehouse full of them. They were spares that had been made for a particular radar system, and somehow had never been disposed of. All of a sudden, 4D32s weren't scarce any more.

    Any truth to that?


    btw, folks probably know this anyway, but just in case:

    The 4D22 is identical to the 4D32 except the 4D22 has a 25.2 volt, 0.8 amp heater (not center-tapped).
  6. N2DTS

    N2DTS Ham Member QRZ Page

    I heard many times that the government released the tubes after the equipment they were spares for was no longer used.
    Its not a uhf/vhf type tube so it seems odd that they would be used in a radar.
  7. WA3VJB

    WA3VJB Ham Member QRZ Page

    I've seen production date codes as late as 1990 on JAN-4D32, and as far as I know, Raytheon was the only manufactuer of that and the RK-4D32. One variant not seen often is a ceramic base, perforated with vent holes and fitted around the existing external pin structure, as if intended to be used with a chimney since it would provide a bit of a seal for air pressure.

    And in the late 1970s I also had heard that the purported uses of this tube included FAA-type radar. I can't imagine the government would actually know when all the gear was discontinued, to then decide to "release" a warehouse full of spares. They'd sooner hit the Dumpster with them, then or now.
  8. N2EY

    N2EY XML Subscriber QRZ Page

    That's the basis of the story I read.

    It's was originally a pulse modulator, which isn't a UHF tube. There are pulse-modulator versions of some popular transmitting tubes, which work well in transmitting applications too.
  9. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    I believe Al, w1vtp, worked for Raytheon and that was story he related on another site.

    I check my four 4D32 spares for my Viking I and two JAN tubes have 12/80 date codes, one JAN tube has a 1/78 date code, and the one in the Raytheon box has a 1/62 date code.

    AC0OB - A Place where Thermionic Emitters Rule!
    Besides, when you're a Ham, you experiment with and improve boat anchors - that's what you do!. [​IMG]
    N2EY likes this.
  10. W7UUU

    W7UUU Principal Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    Wow! I'd never heard of a 4D32 - maybe in passing years ago - sounds like an amazingly rugged tube!

    Cheap too:


    Obviously in great demand, base on how many that seller has sold....

    Why was it never seen more in the Homebrew circles - per Jim's comment about the 6146 coming along very close in time?


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