[BC] when you had to bunk at the station

[Phil Alexander]

I am in the midst of getting ready to leave for Vegas
so there is not time for all this, however it is
necessary to stop the spread of mis-information,
especially about one of the most important pieces
of early day FM history.

It was, is and will ever be Phasitron. Google 2H21
which was the tube's first number and you may find
something.

The Phasitron was an electronic beam tube with
36 grids. Immersion in a magnetic audio field
caused "wobbling" of the three phase RF beam
disc which operated at 1/432 of carrier. A Scott
connection in 1T3 and 1T4 was used to convert RF
to three phase.

Once upon a time I worked on several of these
including rebuilding an exciter which had been
damaged in transit that required replacement of
aforesaid 1T3 and 1T4 although the manual said
that required return to Syracuse. 1T3 and 1T4
had two variable coils and there were five pots
for adjusting voltages etc. Thus, tuning the
exciter to a new tube was a nightmare of NINE
interactive adjustments necessary to achieve
a workable compromise between performance at 30 
and 50 cps audio. Aligning a 6T DA array is simple
and very easy in comparison.

And it was PHASITRON. The tube was GL-2H21/5593.
Using the wrong spelling makes finding correct
information difficult.

These sites may be interesting to those who wish
to learn more:
<http://encyclopedia2.thefreedictionary.com/phasitron>
<http://www.oldradio.com/archives/hardware/ge.htm>
<http://www.radioworld.com/article/7852>
<http://www.w9gr.com/phasitron.html>
<http://louise.hallikainen.org/BroadcastHistory/uploads/GeBT-1-B.pdf>
Warning - this PDF is > 19 megabytes, but is the
REAL deal - an IB for the 250 W GE FM.
<http://www.neazoi.com/technology/phasitron.htm>

Phil Alexander, CSRE, AMD (who cut his teeth on a Phasitron)

-----Original Message-----
>From: RichardBJohnson at comcast.net
>
>General Electric called their phase-modulator a Phasotron and the nameplates of the schematics listed (google Phasotron) in ebay also use that spelling and BTW, it is the current spelling for an electron device that uses an electron beam in a retarding magnetic field, the low-power principle upon which the FM modulator worked.