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February 1931 QST
 Table
of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
from
QST, published December 1915 - present (visit ARRL
for info). All copyrights hereby acknowledged.
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 Visit the ARRL website today for a complete digital archive of QST and their other publications.
Vacuum tubes all required some
level of hand assembly by human workers, at least for positioning grids and attaching/routing
the leads to external connection pins. A 1940s vintage film titled "Electrons
on Parade," produced by RCA, shows how laborious the process was. Tubes like this Radiotron UV-861
tetrode vacuum tube amplifier required a human glass blower to form each one individually, as
opposed to standard tube shells being formed by machine. The operating frequency
is not specified here, other than to say it is an R.F. power amplifier. The "RCA
Guide for Transmitting Tubes" (p41) lists the maximum frequency as 20 MHz. The
price in 1930 was $295, which is the equivalent of around
$5,409 in today's money. By 1943, the date of the aforementioned guide, the
price had dropped to $155.
RCA Victor Company Radiotron UV-861
 A screen-grid 500 watt R. F. Power Amplifier
The best operation of any power circuit is assured when it is equipped with RCA
Transmitting Radiotrons. This is because:
1. They are the result of the longest experience in the commercial manufacture
of power tubes.
2. They are the product of the world's largest and most famous radio engineering
laboratory.
3. They are guaranteed to be free from electrical and mechanical defects.
When you use RCA Transmitting Radiotrons, therefore, you get long service and
the maximum quality of performance.
Radiotron Type UV-861 (illustrated above) is particularly recommended for high
frequency use as a linear (Class B) amplifier. The fourth electrode - the screen
- makes neutralization unnecessary.
UV-861 Rating
Filament Volts: 11 | Filament Amperes: 10
Amplification Factor: 300 | Mutual Conductance: 2.25 Milliamperes/volt
Linear RF Amplifier-Class B | Normal Operating Plate Volts:
3000
Screen Voltage (Approximate):
500 | *Control Grid Bias Voltage:
- 60
Non-modulated Plate Current (DC):
188 M. A. | Peak Power Output:
600 Watts
Carrier output (100% modulated):
150 Watts | *Referred to midpoint of filament
Additional technical data will be furnished upon request.
Engineering Products Division
RCA Victor Company, Inc.
Camden, New Jersey
155 East 24th Street New York City
100 West Monroe Street Chicago, Ill.
Santa Fe Building Dallas, Texas
235 Montgomery Street San Francisco, Calif.
Posted June 26, 2024
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