August 1965 Electronics World[Table of Contents] People old and young enjoy waxing nostalgic about and learning some of the history of early electronics. Electronics World was published from May 1959 through December 1971. All copyrights are hereby acknowledged. See all Electronics World articles. 
Even with the ready availability of programmable calculators and smartphone apps, there are still times when having a handydandy nomograph printed out and hanging on the wall for quick reference can be a great asset. This one provided ready conversion between voltage and power gain to volts or millivolts and watts or milliwatts.
Nomographs Available on RF Cafe:

Decibel Nomograph

Voltage and Power Level Nomograph
 Voltage, Current, Resistance,
and Power Nomograph
 Resistor
Selection Nomogram
 Resistance
and Capacitance
 Capacitance
Nomograph
 Earth Curvature Nomograph
 Coil Design Nomograph

Coil Inductance Nomograph
 Antenna Gain Nomograph

Resistance and
Reactance Nomograph
By Max H. Applebaum
Warwick Electronics, Inc. Pacific Mercury Div.
Power and voltage gain of amplifiers with equal input and output impedances are readily found.
To find the power gain of an amplifier, it is necessary to compute the ratio of its output to input power, take the log and multiply by 10. When the input and output resistances are equal, the voltage gain of the amplifier can be calculated by multiplying 20 times the log of the ratio of output to input voltages.
This nomogram eliminates the tedious calculations involved, and gain can be determined in a much simpler manner.
For values of 10^{n} or 10^{n} times those on the E_{1} scale, subtract or add, respectively, n times 20 db from or to the values on the voltagegain scale. (n times 10 db from or to the powergain scale when the P_{1} scale is used.)
For values of 10^{n} or 10^{n} times those on the E_{2} or P_{2} scales, add or subtract respectively n times 20 db to or from the values on the voltagegain scale and n times 10 db to or from the values on the powergain scale.
Example: Find the voltage gain of an amplifier whose input and output resistances are equal, when 6 volts output is measured for 200 mv. input.
Solution: Place one end of a straightedge over 6 on the lefthand scale and the other end over 200 on the righthand scale. Find 29.6 at the point where the straightedge crosses the center scale. This is the voltage gain in db.
Posted June 4, 2015