1944 BC-610 E back home!

Discussion in 'Amplitude Modulation' started by N6YW, Jan 28, 2019.

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  1. W2VW

    W2VW XML Subscriber QRZ Page

    Were there tubes in the HT-4 that were not Eimac or RCA?

    Anyone here use an HT-4 or 4-B on ten meters?
  2. N2EY

    N2EY Premium Subscriber QRZ Page

    Yes. Here's an ad:


    While the numbers are hard to read, it's clear that they are RK-xx Raytheons.

    The BC-610 was derived from the HT-4, but there were numerous changes to the design before it could meet military specifications. Some were for ruggedness, some for integration into the SCR-299 systems, and some to use different parts. Which isn't surprising; the HT-4 wasn't meant to go bouncing around a battlefield.

    Check this out. How many tubes which are not RCA or Eimac do you see on the list?

    http://www.audiotubes.com/VT crossreference.htm
  3. K5UJ

    K5UJ Ham Member QRZ Page

    How many have ever owned ( or anyone here) a genuine HT-4, i.e. not a BC610? I know of one guy who was nearby and once worked for Hallicrafters (sadly now S.K.). How many have ever owned a real SX-73 (not the mil. version)? Probably Vortex Joe.
  4. W2VW

    W2VW XML Subscriber QRZ Page

    Really interesting! Thanks Jim.

    I see the RK-63 looks similar to the 250TL and the RK-38 looks like a cross between an 810 and a 100TH.

    Always assumed the tube lineup was similar in the older models.

    I have only seen one HT-4 in person and there was no chance of looking closely.
  5. K4KYV

    K4KYV Premium Subscriber QRZ Page

    I have a modulation transformer from one. It's made by Kenyon, slightly different in construction from the Stancor one in the BC-610E. Otherwise same specs and about the same size.
  6. N2EY

    N2EY Premium Subscriber QRZ Page

    You're welcome!

    See QST for December, 1943 - "The Saga of the 299". There are probably other articles.

    WW2 standardized a lot of things. I don't know how many BC-610s were built, but the problem may have been that the production capacity for RK-xx transmitting tubes was less than that for Eimac-type tubes.

    One thing I know for sure is that during WW2 the demand for tubes for the war effort was so great that anyone who could make them could get a license and a contract to do so. Tube quality naturally suffered, but the solution was to have lots of spares.

    Note that ENIAC, the world's first true computer in the modern sense (high speed, Turing-complete, general purpose, electronic digital computer) used very common tube types. The designers got around the decline in tube quality by making the circuits work with wide variations in tube characteristics - and by letting ENIAC run 24/7, because so many failures happened at turn-on.

    If you look at Heathkit products from the 1940s and 1950s, you see a lot of "odd" tubes used. 1626 as a rectifier? 1619 beam power tube as a regulator? 1629 magic eye tubes in test gear?

    The reason is simple: Heath got a great deal on them in surplus.
  7. K4KYV

    K4KYV Premium Subscriber QRZ Page

    Plus, thy were intended for the duration of the war, so tube life wasn't a priority. A good example of that is the 6C21, basically a 450TL running with filament voltage boosted to 8.2 volts to achieve gobs of peak emission as a radar pulse modulator, at the expense of greatly shortened tube life.
  8. K5UJ

    K5UJ Ham Member QRZ Page

    That was true for many companies that made stuff for hams. Eldico was an outgrowth of Surplus Radio and their entire line was made with surplus parts. The TR-1 has a lot of ART-13 parts to it. The reason WRL had so many far out tubes (by today's availability) was that Leo could get zillions of them surplus. I think he got the parts, then got his engineer to design a rig around them.
  9. N2EY

    N2EY Premium Subscriber QRZ Page

    Sure - I just mentioned Heathkit because they're the best known and the biggest.

    But...were they all really surplus? I seem to remember AX9909s or similar being used.

    And it worked the other way too - the 4D32 is a prime example. Note that it is listed in the Allied catalog for decades (until 1970 and probably later) but at incredible prices (the 1970 Allied catalog lists the 4D32 at $74.30, while a pair of 6146As cost less than $9 and a pair of 6146Bs less than $11).

    Edited to add: the last listing for the 4D32 I found in the Allied catalog was 1973. $82.47 for a single 4D32. A pair of 6146As in the same catalog was $9.98, a pair of 6146Bs was $12.22

    Whether Allied actually had any 4D32s is a different question.....
    Last edited: May 15, 2019
  10. N2EY

    N2EY Premium Subscriber QRZ Page

    Yes, particularly since much of the equipment probably wouldn't survive long in combat.

    I seem to recall that some versions of the famous Rolls Royce Merlin engine were meant to get a major overhaul every 500 hours.....which doesn't sound like much, but is a very long time when people are shooting at you.

    Did you mean 1000T? Most of the references I have found list the 6C21 as being derived from the 1000T. Its filament current rating is closer to the 1000T than the 450TL.

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