From the time Lee De Forest put a grid in the diode detector which he patent in 1906 to build the first audion (what he named the first triode which he patent
in 1908) amplifier engineers have struggled to build amplifiers with less spurious noise. An amplifier can not amplify a signal that is much lower then the spurious noise generated by the active device. This is the noise you hear in an AM radio when it is turned on with no antenna or signal or the noise that can be heard when a public address system is turned on and I don’t mean the squeal caused by the mike getting to close to the speaker. This is not to be confused with static which is atmospheric noise.
Very high gain amplifiers could be built even in the 1940’s and 50’s but they
were of very little use if the signal to be amplified was so weak that the noise generated by the amplifier covers over the desired signal.
The vacuum tube uses a hot cathode to emit electrons which are attracted to the positively charged anode (plate). This process generates a phenomenon known as “thermal noise”. Fortunately solid state amplifiers do not suffer with this problem but in the 1950’s and early 60’s the solid state
industry was just getting started. The first commercially available integrated circuit was in 1961 and they were a far cry from what we see today.
As more and more satellites were being sent up so there was a greater need for
low signal amplifiers. In 1958 the last significant receiving tube development was made available by the RCA Company. This little tube that was smaller then the end joint on a dainty lady’s little finger was called a Nuvistor. With this new device high gain amplifiers with relatively little noise could be built.
The Nuvistor could probably best be described as a little a vacuum tube in a metal can. They were developed mostly for industrial and professional applications but they caught the attention of some tinkerers, yours truly being one, that were fascinated
with the potential of this newest child of the De Forest generations.
The little tube bridged the gap for a few years and did a magnificent job but the life of the Nuvistor was doomed from its birth as the solid state industry grew and put the foot or hand warming amplifiers out to pasture.