[Milsurplus] Pre-WWII Aircraft Radio Transmitters

[Mike Morrow]

Ray wrote:

>More on the primitive GO series, the pre 7 GO transmitters used two 860
>(VT-17) tubes in a MOPA circuit and  that tetrode was introduced
>in March of 1929, a oscillator PA type transmitter of that era (1930-33)
>would be inherently unstable and produce little power at frequencies
>above 20 MHz.

The information that Dewitt provided only told us:

(1)  Details of the 1933 GO made by Hygrade Sylvania.
     We have *NO* information telling us that any details of the GO apply
     to the later GO-series.  In fact, it's a safe bet they don't. 
     Hygrade Sylvania was in a world of its own.
(2)  Details of the 1937 GO-3 and the 1940 GO-9 made by Westinghouse.
     From the almost identical tube lineups it's a safe best that the
     GO-3, -7, -8, and -9 made by Westinghouse are similar, as one would
     expect on units from the same manufacturer, except for upper frequency
     limit.

We are still without many technical details of the GO-* made by the other
two manufacturers:

1934 GO-1 Western Electric  Highest Freq = 13575 kHz
1935 GO-2 Western Electric  Highest Freq = 13575 kHz
1938 GO-4 General Electric  Highest Freq = 26500 kHz
1939 GO-5 General Electric  Highest Freq = 26500 kHz
1939 GO-6 General Electric  Highest Freq = 26500 kHz

One thing we'd probably be safe in saying is the NONE of these use ANY of
the RF tubes in the original GO.  We'd also likely be correct in predicting
that GO-1 and GO-2 are similar (maybe even identical), and also that GO-4,
GO-5, and GO-6 are similar (maybe even identical).  And money could be made
betting that there are significant differences between the WECO models and
the GE models, and between these models and GO, and between these models
and GO-3/7/8/9.

>I can see the older series GO transmitters working great up to 9 or 12 MHz
>but 25 or 26 MHz another thing entirely.

All ten models of the GO-* covered up to *at least* 13575 kHz, including the
original 1933 GO.  It must have work acceptably, otherwise there would not
have been so many different orders for the GO-series, nor so many RU-* liaison
receivers to go with them that had 13575 kHz as their upper limit.

>all reasons to support a radical redesign as evidence by the apparent
>difference in GO-7 and above transmitters.

Why are you assuming that characteristics of the tube lineup of a 1933
transmitter made by one *odd* vendor can be applied to models that were
made years later by two other vendors (Western Electric, General Electric)
that are completely unrelated to the original? 

> Need a schematic to answer that question.

That's certainly true.  I'd love to know more about the WECO GO-1/2 and
especially, the GE GO-4/5/6.  I believe for the GE sets, in particular,
the development of an aircraft transmitter fully capable of operation at
26.5 MHz in 1938 was a technical achievement about which it is worth knowing
more.  It's as remarkable as the BC-224 was in 1937.  What's the chance
that manuals even exist any more for these transmitters?

Mike / KK5F