4CM400,000G is probably costing around $45K new, but I am guessing.
The 4CM300000GA was $38K three years ago when I inquired.
It is not the highest power tube, but strictly radio transmitters, it
is one of them. The 4CM500,000G and the TH558 are the big boys for SW
broadcast, in thermionic devices. The X2159/8974 tetrode is certainly
a higher output power device, but is best for VLF and MW
transmitters. The Saudi's used them for a megawatt or two at one
time, I was told. But then they got the Harris solid state megawatt
rigs, with many transistors.
A year or so back, the VOA reduced the usage of 4CM300,000G or GA so
a lot of these tubes might be on the surplus market. These are
similar to the Thomson TH537. They were PDM modulators, now replaced
by solid state devices, in a massive retrofit by the manufacturer.
We have some 8974's at 50 MHz, in single pulse operation. They supply
a few MW (we think) but nobody put a real peak wattmeter on the
output. It only pulses once every 15 minutes or so, so the average
power is nearly zero. Driver is a 4CX15,000A.
The biggest bottle for RF coming out of San Carlos is the
X2274/4CM2500KG. It is a pyrolytic graphite gridded monster, for RF
power of a megawatt (CW) at up to 100 Mhz or so. Not too many
operating, the best example of operation is in Japan. These tubes
were targeted for long pulse (15 seconds) ICRH fusion applications.
I hope to have data and pix of a bigger bottle, the TH628 Diacrode,
from France, once we get it in the socket. First we have to build the
socket. Thats happening right now, and i hope to have cold network
analyer sweeps in a few months, and power by the spring of 2001. It
is a 3 MW peak, 600 kW CW amplifier, for 200 MHz. We have s/n 01 of
the production tube, and a need to replace four GG triode amplifiers
with this GG/GS tetrode amplifier, once we have the prototype
working. Anybody looking for work in high power RF?
73
John
K5PRO
Los Alamos Neutron Science Center
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