These days the production lifetime of semiconductors is extremely short
compared to the life time for tube designs back in the day.
When key integrated circuits or custom designed chips are no longer
supported by the vendor, or the vendor closes down, or is bought out,
and their lines discontinued or altered, there is not much a
manufacturer can do but drop a product that has too many of the devices
that become obsolete or much higher priced. Designs are much more
integrated in solid state; but there were examples of tube designs that
could not continue with original tube selections. As recently as Yaesu
FT 101 rigs, a sweep tube became unavailable, and a conversion to the
venerable 6146 at higher cost had to be made.
Final bi polar power RF transistors have had a stormy, rocky road of
lifetime. With the demise of Motorola many mainstays of the RF world of
finals were taken away, and then the reorganization of Philips
semiconductor manufacturing, altered the market in Europe and much of
the world.
Unless a semiconductor was widely used by the military groups of the
world, it may not have a long lifetime. A few of the standard logic
families widely used in government projects were picked up for sustained
supply by Lansdale Semiconductor, to support legacy equipment.
It almost seems before designing a new radio, the engineer needs to
assess the fiscal stability of the transistor makers, the long term
outlook for that logic or RF family, and only then see if, oh by the
way, something might be good enough for the circuit design.
-Stuart Rohre
K5KVH
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