ARLA/CLUSTER: Existe ainda espaço para equipamentos a vavulas?

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Is there still room for the vacuum tube?

An interesting story from EE Times Europe.
This warms the heart of those of us brought up on Valve technology!

Feature Articles
Is there still room for the vacuum tube?
July 02, 2014 | Peter Clarke | 222906503
Bill Schweber asks if there is still a use for some of the old analog
components; in particular the vacuum tube, otherwise known as the
valve.

For most electrical engineers, the vacuum tube or, more formally, the
vacuum electron device (VED), is a quaint curiosity and artifact of
the past, and with good reason: The world of solid-state transistors
and ICs is where most electronics is these days. Advanced versions and
extensions of Lee DeForest's 1906 Audion triode – the first electronic
analog amplifier – were critical to making our industry the powerhouse
it became. Look at the products of the first half of the 20th century:
It's astonishing what skilled scientists, engineers, and manufacturers
accomplished using these devices. Even the classic five-tube AM radio,
which brought wireless to millions, is an outstanding example of
design, cost-effectiveness, and performance.

Various 12AU7 (ECC82) Vacuum Tubes / Valves (Courtesy of Diy Audio Projects.com)

Though no one today is going to build a VED-based computer or
cellphone, there are still plenty of VEDs in widespread use. Start
with the ubiquitous microwave oven in almost every home: It has a 2.4
GHz, 1 kW magnetron (a typical unit's maximum power) to excite the
water molecules in the food.

But the use of VEDs goes well beyond that single mass-market
application. I was surprised to read a summary of a report “Microwave
and Millimeter Wave High-Power Vacuum Electron Devices: Changes Are
Looming on the Horizon” from ABI Research, which claims the annual
market for specialized VEDs for military/aerospace markets is over $1
billion annually. Depending on where you sit with respect to the
active-electronics components business, that's either a big chunk of
money or too small to really think about. The key sentence from the
summary is this: "These tubes remain essential elements in specialized
military, scientific/medical, and space communications applications."

Reality is that if you need tens of RF watts, at frequencies in the
GHz range and higher, or kilowatts for your TV broadcast transmitter
in the 100-to-500 MHz range, you're looking at a VED solution. If you
are working with microwave and millimeter waves and need high power,
you don't have much choice -- at least, not yet.

But what about the future of VEDs?

Predictions about the future are always risky, as any look back at
predictions made in the past shows. Still, the report notes that
devices based on gallium nitride (GaN) may make significant inroads
over the next few years, judging from products that are available now
from many vendors or in the immediate pipeline. Perhaps that magnetron
in your microwave oven will go GaN solid state before too long?

Nonetheless, for the foreseeable future (which is an unknowable period
in the high-tech world), VEDs are here to stay in one form or another,
with their wonderful names such as klystron, magnetron, traveling wave
tube (TWT), crossed-field amplifier, to cite just a few of their many
versions. I just hope that as their use declines, we don’t lose the
manufacturing "secret sauce" it takes to make these complex marvels of
glass, metal, and ceramic, which can calmly produce and dissipate
kilowatts and more.

Are there any other products you know of that we might naïvely assume
are "obsolete" (such as the electromechanical relay) but which are
actually still going strong?

Bill Schweber, is an engineer, author and editor and this article
first appeared on EE Times' Planet Analog website.

Our thanks to John, G8MM for spotting this item