Years ago I saw some vacuum packaged 4CX 250B tubes, at a military base MARS
station.
The 250Bs, were in OD green cans about half the size of a can of chili and had
molded plastic suspension inserts that kept the 4CX 250B softly floating in the
can. The can was evacuated, and when you needed the tube, you pulled the pop
top ring and pealed the top cover off the can, with the very recognizable
tseeeeeeeeee sucking sound of the broken vacuum the instant you cracked the can
open. I imagine that it would be useful for ham-consumer use, if one designed
a similar container to store a tube in, that you could evacuate, and seal off,
with ordinary (compressor in reverse) equipment. Maybe one of those food
vacuums that suck air out of plastic food (or for that matter, clothing)
containers. I dont think you would have to have anything close to a perfect,
or hard vacuum to be useful. If you lowered the air pressure inside by several
orders of magnitude, (I don't know how much of a vacuum is easy to produce)
with simple equipment and were able to seal off the por
t, with the tube inside, the differential pressure inside the tube and outside
the hard vacuum tube would be reduced substantially, perhaps substantially
reducing the ingress of gas inside the tube over time. If a ham had his set of
spare 3-500Zs in the closet inside such a vacuum jar, (periodically re cycled
with the reverse compressor to keep the vacuum,) the tubes, might have
substantially longer shelf life, and he (and tube makers) might buy such a kit
accessory for their tube storage.... what say?
Best Regards,
73, de Pat Barthelow AA6EG
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