Any RCA 806 tubes to be had?

Discussion in 'Amplitude Modulation' started by W7TFO, Jun 11, 2017.

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  1. N2EY

    N2EY Ham Member QRZ Page

    Of course! But....take a look inside the BC-610....

    There's a 250TH and 2 100THs, by Eimac, all right. Also a pair of 866As, two 5Z3s, a 6V6, two 807s, two 2A3s, and 3 0D3s.....all RCA designs.

    There were a considerable number of BC-610s made.....but a lot more ARC-5. Consider the tubes used in the ARC-5 series....the BC-312/342 and BC-348....

    seems to me RCA let Eimac have the big glass transmitting tube end of things, and took the receiving and small transmitting tube part.
  2. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    I have seen G-E and Sylvania VT- tubes, but those may have been manufactured after the war. I'm not sure if RCA made the 813s for the ART-13 transmitter or not. I have seen large transmitting tubes with VT- numbers and JAN markings, made by United Electronics as well. But since RCA had a virtual monopoly on tubes for so long, that may have carried over when manufacturing of smaller receiving type tubes was stepped up for the war effort.

    Interestingly, Heinz-Kaufmann manufactured a line of "gridless" transmitting tubes. Instead of using a grid to act like a valve regulating the electron flow, they used deflection plates, kind of like the ones in a CRT to sweep the electron beam across and away from the plate, to control the electron flow. This might have worked for class-C service, but I don't know how linear it was, so it may not have worked for class B and class A modulators and linear amplifiers. They were advertised in mid 1930s west coast Radio handbooks. According to the ads, this was supposed to be a new, more efficient design, because it used zero grid driving power. But in reality, this was an attempt to circumvent RCA's patent monopoly on tubes. This concept didn't last very long, since H&K eventually got a licence from RCA to manufacture conventional tubes, so evidently they didn't work very well, or H&K would have continued to make them and maybe revolutionised transmitter design.
  3. W7TFO

    W7TFO Premium Subscriber QRZ Page

    Please go back to the earlier post #3, I attached the PDF of 'Defiant West', the Eimac story.

  4. N2EY

    N2EY Ham Member QRZ Page

    I think what happened is that, during the war, all sorts of tubemakers built whatever was needed - if they had the facilities and if there was a defined military need. But they were all built under license from the tubemaker who originated the design.

    Wouldn't you like to have a penny (in 1945 money!) for every tube in an ARC-5 transmitter or receiver, regardless of who actually made the tube?

    The VT list also the tubes on it "popular" in the minds of all who dealt with tubes during the war, and de-popularized those tubes that weren't on the list. The 807 and its 12 volt sibling the 1625 are extremely well known, the HY61 (Hytron's version) is rare. Raytheon's RK- series and Taylor's T- and TZ- series practically disappeared......but we all know the 811 and the 813.
  5. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    Here is another titbit regarding WWII surplus tubes. The gov't must have purchased a jillion 211/VT4-C tubes for the BC-191 and BC-375 transmitters (which were already obsolete years before Pearl Harbor); those are one of the tubes the audiophools go apeshit over and have driven the price of a 211 up from less than $1 per tube to triple-digits. I use a single 211 in the driver stage of my HF-300 rig, but fortunately, I acquired plenty of spares before the price jumped up. Looking over the conversion charts, I see two VT- versions: The VT4-B is listed as the 211, while the VT4-C is listed as the JAN 211. crossreference.htm

    I thought the JAN prefix stood for "Joint Army-Navy" and meant only that the tube was produced under military contract, and had nothing to do with the characteristics of the tube. I have no clue what the difference is supposed to be between a 211 and a JAN 211 other than its production history.
  6. N2EY

    N2EY Ham Member QRZ Page

    Here's what I think that's all about....

    (the following is from memory)

    The 211 is a pretty ancient tube, dating from the 1920s. (See QST for April 1929 - "Modern Practice in High-Frequency Radiotelephony" - shows the UV-211 as a Heising modulator).

    Such early tubes often went through a series of improvements over time - better element supports, ceramic insulators, carbon vs. tantalum anodes, etc. Which leads me to suspect that the VT-4 is the original old-school 211, the VT-4A an early improvement, the VT-4B a later improvement, and the VT-4C the latest of all, with changes specifically required by JAN. (The BC-191/375 was used as an aircraft as well as "portable" ground transmitter, so the changes probably had to do with making the tube more rugged.)

    Just a speculation mixed with memory of stuff read....but it makes sense, doesn't it?
  7. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    Earlier versions of certain triode tubes carried the prefix UV. Later versions, UX.

    With receiving tubes, like the UV-201 and UX-201A, UV sockets usually used bottom-wiping contacts and the tube pins were solid brass; UX usually used side-wiping, and the pins were hollow. UX tubes were provided with bayonet pins to make them back-compatible with older UV sockets. A UV socket will take a UX tube with a bayonet pin, but a UX socket will not accept a UV tube since the pins are too small a diameter (and often too short). As for the larger base transmitting tubes, they all have the bayonet pin. Most sockets are side-wiping, but some like the ones in the BC-375/191 are bottom wiping. The latter tend to be prone to failure, since electrical contact is entirely at the solder blob at the bottom of the pin. The ancient bottom-wiping 4-pin receiving tubes had a solid brass pin with no solder blob at the bottom.

    As I recall, the older UV types had tungsten filaments, while later types used thoriated tungsten filaments.
    The pure tungsten filaments drew several times more current than do thoriated tungsten. For example, the 5-volt UV-201 receiving triode pulls 1 amp while the UX-201A pulls 0.25 amps.

    I believe the UV-203 and UV-211 had tungsten filaments; the 203-A and plain 211 have the thoriated.

    Early 5-pin receiving tubes carried the UY prefix, e.g. UY-227, later just plain "27".

    I was able to find this (on an audiophile/audiophool forum, so take it FWIW). Links are removed because none of them worked, but some of the historical information might be correct:

    UV211 was developed from UV203 accompanied with 203A

    I found the GE's Research Laboratory manual for Signal Corps.
    They said UV211 was low mu version of UV203A.
    UV211 & UV203A was born from UV203 with thoriated tungsten filament.
    UV203 has tungsten filament & UV211 and UV203A have new type.
    The thoriated tungsten filament is called as "XL tungsten filament".
    UV211 was designated as VT-4-B on 1st July 1923
    before WE 211D was manufactured.
    In 1923 WE211A/VT-4 & UV211/VT-4-B were used in Signal Corps.
    Later WE211D was manufactured & designated as VT-4-B.
    N2EY likes this.
  8. W8KHK

    W8KHK Ham Member QRZ Page

    Very good read! Thanks for sharing! Could you share some specifics on the origin of this document? 73...
  9. W7TFO

    W7TFO Premium Subscriber QRZ Page

    A lucky internet search...around the MIT archives.

  10. K5UJ

    K5UJ Ham Member QRZ Page

    Thanks for posting that pdf file DG--it has been most interesting and a lot revealed about the early days of tube manufacturing. Bay area was a technology incubator long before "silicon valley." More like "vacuum valley."

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