Warm-up Time
Most valve sets needed a few seconds for the valves to heat up, though there were exceptions. Warm-up times changed as valves went through several generations of design.
- Bright emitter valves universal in the early 1920s came on in a small fraction of a second, effectively instantly.
- Direct dull emitters typical of the late '20s and 1930s came on in around a second. This type of valve continued to be popular in battery sets for several decades more.
- Indirect emitters used in more or less all mains valve radios from the late 1930s onward were slow to reach emission temperature, with wait times routinely exceeding 10 seconds.
- The last generation of valves was nuvistors. These tiny devices reached emission temperature fairly quickly.
Read more about this topic: Antique Radio
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