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 May 1939 QST 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.

The ARRL (American Radio Relay League) might be considered as one of the first app developers. At 50¢ and \$1 per app, the price was in-line with one of today's typical not-for-free Apple or Android app. A user willing to shell out \$4 for all six had at his fingertips calculators and reference tables for capacitive and inductive reactance, resonant frequency, gain and power, conductor amperage, transformer turns ratio, resistor, capacitor, and inductor series and parallel combination, and other values. These six apps, dubbed "Lightning Calculators*," were comprised of bit of cardboard, plastic, and a metal eyelet, not data bits. Here is a for-real Type B "Lightning Calculator," graciously provided by Joseph Birsa, N3TTE.

* "Lightning" meaning lightning fast, not calculators for working out problems about lightning from the sky.

Lightning Calculators

Six Types Solve All Problems

Type A - For problems involving frequency, inductance and capacity, in design of radio frequency circuits. Direct reading answers for size of coils and condensers for any range between 400 kc. and 150 mc. Price, \$1, postpaid.

Type B - Gives direct reading answers to calculations involving current, resistance, voltage and power with scale for resistance of copper wire and scale for calculating decibel gain or loss. Price, \$1, postpaid.

Type C - More information on electrical conductors than you could find in a book full of tables. Price, 50c, postpaid.

Type D - Gives decibel gain or loss when in-put and output voltages, currents or power are known. Price, 50c, postpaid.

Type E - Direct reading total resistance of resistors connected in parallel, and total capacity of condensers connected in series. Price, 50c, postpaid

Type F - Permits measurement of resistance, from 1 ohm to 1 megohm by use of a voltmeter. Makes an ohm-meter of your voltmeter. Price, 50c, postpaid.

American Radio Relay League, Inc., West Hartford, Conn.

Posted May 25, 2022
(updated from original post on 5/18/2016)