[BC] The last of the tube 1000 watt transmitters

[RichardBJohnson at comcast.net]

Eimac's help was both a blessing and a curse! The same with
Northern Engineering! I got the tubes, sockets, chimneys and
plate-caps for "free" from Eimac once they were convinced that
I could actually build the transmitter. Then they gave me "help"
which meant that they had copies of all the data which allowed
them to "consult" with other manufacturers who were anticipating
new designs. The only real technical help was Bill Orr's suggestion
for the grid resistor value in the finals and the bias voltage
necessary to get the correct range of idle currents in the
modulators; like do I need to build a 300 volt bias supply or
a 200 volt one?

I'm sure that when CCA was anticipating building their 1 kW
transmitter they contacted Eimac and got some advice about the
tubes to use. Naturally Eimac wanted to increase the size of the
customer base for a particular tube.

BTW, there were NO solid-state devices in that rig. It had
816 http://www.classiccmp.org/rtellason/tubedata/816.pdf
mercury-vapor rectifiers for the HV and 5R4
http://www.triodeel.com/5u4_p1.gif duo diodes for the LV and
bias supplies. It also had NO electrolytic capacitors. In my
opinion (at the time) they were unreliable consumer junk with no
place in broadcast transmitters. This meant that I had a lot of
filter chokes as well as oil capacitors in the supplies. 

About the vacuum crystals; I was the guy who petitioned the
FCC to remove the requirement for crystal ovens (and thermometers BTW)
so that me and others to follow could take advantage of the new
technology. Much later, I put the first programmable frequency control
in Broadcast transmitters (a Hughes PLL chip and a fixed-frequency
crystal). Before that time every transmitter had a crystal ground
to their specific frequency. This was before the first all solid-
state transmitter that Harris claims as the first, but in fact my
SS1000 (Cetec/Sparta) was Type Accepted and in production when
Harris's first contraption with the light bulbs was still being field
tested in Kalamazoo.

I did a lot of original work when I was designing broadcast
transmitters and many of the other companies followed the example.
They didn't necessarily copy my work because once an idea is proved;
it is relatively easy to improve upon it. The companies I worked for
were often the risk takers which allowed me to stay at the forefront
of the rapidly advancing technology.

Cheers,
Richard B. Johnson
Book: http://www.AbominableFirebug.com/

----- Original Message -----
From: "c gennaro" <cvgennaro at gmail.com>

Your design was exactly the same as used by CCA in their AM1000D's in
the late '60s ;)

Chuck Gennaro
Central Wisconsin